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Project Description;
Molecular photoruptures; energy properties and mechanisms
Content list:
pages:
A. State of the art …………………………………………………….. 2 B. Scientific
objectives and originality……………………………….
a) Objectives b) Originality
6
C. Research methodology, time plan and milestones………………… 8 C. a)
Research methodology.
C.a. 1) Quantitative, qualitative and energy resolved analysis
of radicals and ions formed by laser multiphoton
absorption……………………….
8
C.a.2) Data from A(see above) are analyzed by use of simulation
models developed within the research group at University of
Iceland……………….
10
C.a.3) Tracking Photorupture paths 1) by femtosecond laser
spectroscopy at Bergen University and 2) by kinetic energy
measurements of fragments in Germany………………………………..
11
C.a.4) Ab initio spectroscopic parameters and REMPI
Spectra……………………………………………………
14
C.b) Project plan………………………………………………… 15 C.c) Time plan and
project emphasis………………………….. 16
D. Co-operation (foreign and domestic) and collaborators
contributions, based on present status………………………….
16
E. Gradute student contributions (partly repeted above). 18 D-E.
Estimated contributions in terms of manpower / man-month (mm) 18 F.
Proposed deliverables and impacts………………………………….. 19 G. Proposed
publications of results…………………………………….. 20
References……………………………………………………………….. 20
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A. State of the art Molecular photoruptures (i.e.
photodissociation and photoionization) play vital rule in processes
such as,
a) –ozone depletion, where chlorine atoms react with ozone after
photodissociation of chlorine containing compounds.
b) –formations of organic molecules in interstellar space, which
are believed to occur by reactions of ions and/or radicals after
photoruptures of smaller compounds.
c) – photosynthetic processes as alternative processes for
productions of chemicals in industry or pharmacy.
d) Capability and expertise to perform research studies in the
above mentioned fields (a-
c) at University of Iceland is based on a facility which has
been built up in recent years to do Resonance Enhanced MultiPhoton
Ionization (REMPI) experiments and detailed analysis.
e) Various methods have been used to study photodissociation and
photoionization processes in molecules. Most of these methods are
based on the use of lasers or laser spectroscopy. i) Recently
energy-excitations and spectroscopic methods based on the use of
ultra-short laser pulses on the femtosecond time scale (10-15 sec.)
have allowed such processes to be studied in detail as a function
of time. ii) Kinetic energy resolved measurements of ion products
in photoionization processes are powerful tools to study
photorupture channels.
f) Most theoretical work on molecular properties deal with
molecules in ground electronic states. Recently number of standard
ab initio methods have been developed to handle excited states of
molecules which wait to be approved.
-------------------------------------------------------------------------------------------------------------
a) Generally it is believed that ozone depletion due to chlorine
containing reagents (RCl) such as the CFC´s is due to
photodissociation processes of the molecules in the stratosphere
forming chlorine atoms (Cl) [1-3]. The chlorine atoms are reactive
radicals catalyzing reaction of ozone with oxygen atoms: RCl + hν �
Cl + R; photodissociation; hν represents a photon. O3 + Cl � ClO +
O2 ClO + O � O2 + Cl This kind of information have caused reduction
in production of CFC worldwide, as is well known. In addition to
the CFC´s various other basic chlorine containing compounds can
release chlorine atoms by photodissociation in the stratosphere,
such as chlorine (Cl2) and hydrogen chloride(HCl). These can either
be formed in the stratosphere after photodissociation of CFC´s or
by diffusion from the earth surface. In recent years the
photochemistry research group at University of Iceland has been
involved in studies of these molecules and other related compounds,
mainly to map molecular energy structures [4-24]. Limited
information are available about transfer processes between energy
states and the actual photodissociation processes on a quantum
energy level scale. In last few years two research groups have used
the photofragment imaging technique coupled with REMPI for studying
the hydrogen halides to reveal several ionization channels[25-29].
Very recently our group has
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developed and used a two-dimensional REMPI (2D-REMPI) technique
to characterize and quantify state transitions within
electronically excited HCl molecules. This work has been accepted
for publication in J. Chem. Phys. in November, 2008[24].
b) Generally reactions of ions and radicals formed by
photorupture of small molecules or
atoms in the interstellar medium are believed to be the source
of bigger molecules. Big organic molecules, formed in such way,
along with water molecules, could be the source of life in space
analogous to that on earth[30-32]. Examples about rupture- and
reaction- processes important for formation of basic ions and
moleculs in organic- and bio-chemistry are seen in the figure below
(Figure 1). Due to interests along these lines there has been a
growing emphasis on studying photorupture channels of small
molecules in the field of astrochemistry [33-35]. Just recently our
research group performed studies along these lines on photorupture
of acetylene[36]. In a paper which we published in Chem. Phys.
Letter this year[36] , photodissociation channels of neutral
acetylene molecules are shown to be important channels for further
ion formations from the fragments.
Figure 1. Ion and molecular formation processes following cosmic
and UV radiations in interstellar space.
c) Emphasis on photoassisted synthesis is growing in the
chemical industry and
pharmacy. Reactions which do not easily occur by traditional
means by controlling temperature or pressure conditions may occur
more easily by photoassisted pathways. Classical example is
isomerization of the organic molecule stilbene and its
derivatives[37]. The cis-conformers of stilbene compounds are
difficult to produce by
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thermodynamic means since the trans conformers are more stable,
hence are the major species formed at thermal equilibrium.
Electronically excited species are formed by photoexcitation of a
mixture of stilbene-isomers in the visible and UV spectral region.
The π bond-rupture mechanisms involved in the isomerization process
differ largely in the excited state compared to that in the ground
state. (See figure 2). Thus, approximately 90% cis- stilbene (10 %
trans-stilbene) is formed by photolysis[38]. The photochemistry
research group at University of Iceland has worked in this field
and published papers on the effects of substituents on
photostationary states of stilbene derivatives[39, 40].
Excitedstates
Groundstates
Energy
Figure 2. Photoisomerization af stilbene.
d) Capability, expertise and facility to perform research
activities in the above mentioned
fields at University of Iceland: Facility to perform resonance
enhanced multiphoton ionization (REMPI ) studies of molecules has
been built and developed in the Science Institute, University of
Iceland in recent years. First, it involves use of equipments
suitable to perform multiphoton absorption and ionization of
molecules, using high energy laser pulses, as described in more
detail below in the section „C.a) Research methodology“. Second it
involves a simulation analysis technique which has been used and
developed within the research group and allows determination of
molecular energy properties. Descriptions of work in this field can
be viewed in numerous publications by the group listed in enclosed
publication lists. Just recently a new high-power and
high-efficiency dye laser, bought by supports from RANNIS and the
University of Iceland research fund, has been inserted
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into the equipment set-up. This has improved measurement
sensitivity and accuracy tremendously. Within the last year the
research group has worked on developing a model and an analysis
technique, based on ion intensity interpretations coupled with
perturbation theoretical treatment to evaluate state interaction
strengths and contributions to photorupture processes. Results
relevant to photorupture of the the molecule HCl will appear in J.
Chem. Phys., November issue, this year (2008)[24].
e) i) Femtosecond spectroscopy. Following development of
femtosecond (10-15 s) laser pulse equipments before about 1980 the
use of the technique to study processes on this timescale has grown
tremendously. Among processes which physical chemists have
emphasized to study by using this technique are molecular
dissociations, which typically occurs within picoseconds (say in
10-12 - 10-13 sec). Professor Ahmed Zeweil in Caltec., who was
nominated the nobel price in 1999 for his studies, is among
pioneers in this field[41, 42]. Typical experiments in this field
are based on energy excitations of molecules by use of femtosecond
laser pulses followed by absorption measurements by femtosecond
pulses (see figure 3). In those cases laser pulses are typically
focused on a molecular beam in a gas phase (see figure 4) followed
by laser pulses from the same laser source after a delay on the
femtosecond time scale for absorption measurements. The time delay
is performed by increasing the path of the absorption (latter)
pulse relative to that of the excitation(former) pulse. As long as
the absorption depends on the distance between the atoms in the
dissociating bond the dissociation process can be mapped indirectly
by performing such measurements as a function of the time delay.
Experiments of this kind require sophisticated and expensive
equipments in a vibration-free laboratory. One such is the “Bergen
multiphoton Laboratory” in the physics department, University of
Bergen run by the applicants collaborators. The main applicant and
his coworkers have been involved in femtosecond laser analysis
before, relevant to photoisomerization studies of the stilbene
derivatives mentioned above. This is presented in reference[39].
ii) The velocity map imaging technique where photoions and/or
photoelectrons with the same initial velocity vector after
dissociation / ionization are mapped onto the same position on a
detector is a powerful tool to investigate photorupture
mechanisms[25-29, 43-45].
A-B#
A-B
A + B
Formation by use offemtosecond laser pulses
Absorption measurements by femtosecond laser pulses
A-B#
Figure 3; Femtosecond analysis of an AB bond rupture.
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Figure 4. Schematic diagram showing a femtosecond experiment. f)
ab initio calculations:
Most theoretical work relevant to molecular properties deal with
molecules in ground electronic states. Recently number of standard
ab initio methods have been developed to handle excited states of
molecules. Equation-of-motion coupled cluster theory (EOM-CC)[46]
has been shown to reproduce experimental excitation energies very
well in certain cases [47]. It is of great interest to apply such
methods at different levels with a number of basis sets to study
the potential energy curves relevant to electronic excitations and
photorupture processes.
B. Scientific objectives and originality; a) Objectives:
Knowledge of photorupture (i.e. photodissociation and
photoionization) processes, important in fields such as ozone
depletion and formation processes for organic molecules in
interstellar space, on a quantum energy level scale, is limited. In
the past, the photochemistry research group at University of
Iceland, has emphasized to study energy properties of
electronically excited state of molecules. Very recently we started
to look at energy transfers between excited states and relevant
photorupture channels in molecules. These first attempts to study
photorupture channels have proven promising as seen in our most
recent publications this year on acetylene[36] and
hydrogenchloride[24]. We now whish to make use of our former
experience and knowledge about excited state molecular species and
the facility which has been built within University of Iceland and
expand our work towards studying photorupture channels of molecules
important in the above mentioned fields as well as in the field of
photosynthesis. In collaboration with colleges in Norway, we plan
to make use of a facility at Bergen University to perform
femtosecond spectroscopy studies for the same purpose. Furthermore,
experiments to determine kinetic
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energies of relevant fragments are planed to be performed by
collaborators at the Technische Universitaet Braunschweig in
Germany. The collaboration subproject are beneficial for all
partners and will broaden our and the collaborators view and
knowledge in fields of new techniques and theories.
b) Originality of the project is based on: 1) -Experimental
determinations of photorupture channels and channel contributions
by the
2D-REMPI. Apart from our first promising attempt along these
lines of study this year[24] this method has not been used before
by others. The 2D-REMPI analysis technique coupled with
perturbation theoretical treatment to evaluate state interaction
strengths and contributions to photorupture processes has been and
is planed to be developed further within our research group.
Briefly, ions formed by resonance enhanced multiphoton ionization
(REMPI) are characterized and quantified as a function of laser
excitation energy. The data are interpreted by quantum theoretical
methods and simulations to derive information about photorupture
channels and its contributions for chosen molecules. See text in
frame below for further clarification / specific example.
Photorupture mechanism of HCl following resonance enhanced
excitations to Rydberg states.
HCl
HCl*
HCl+
H+
E V
H+Cl+
H+Cl-
H + Cl* H* + Cl
Figure 5. Major photorupture channels for two-photon resonance
enhanced excitations to Rydberg states. In figure 5 are shown major
photorupture channels following two-photon resonance enhanced
excitation to a Rydberg state[24-26, 28, 29]. Initially a Rydberg
state (HCl*; Ry) is formed by two-photon excitation. HCl* can
transfer to an ion-pair state (H+Cl-; V). Further photon absorption
of (HCl*; Ry) can form HCl+ and H+, whereas H+ and Cl+ are the
major ion products of further excitation of (H+Cl-; V) via H* + Cl
and H + Cl* intermediates. Measurements of relative Cl+ and HCl+
ion formations allow determination of interaction strengths between
the Rydberg state (Ry) and the ion-pair (V) state as well as
relative contributions of the two states to the photorupture
channels.
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2) – use of simulation programs for two- and three-photon REMPI
spectra to characterize
energy properties of excited states involved. The model /
program has been developed and is under continuous construction
within the photochemistry research group in. U.I.
3) –combination of 2D-REMPI studies (in Iceland), femtosecond
spectroscopic studies (in
Norway) and kinetic energy resolved studies (in Germany) in
order to resolve photorupture mechanism of molecular systems of
interest in fields related to ozone depletion, organic chemistry in
interstellar space and photosynthesis.
4) –simultaneous search for new (i.e. not previously observed)
electronic states of
molecules capable to be observed by multiphoton absorption
only.
5) –the use of standard available ab initio methods (different
levels and basis sets) rather then state-of-the-art work[48, 49] to
explore properties of PES for electronically excited states of
molecules and to carry the theoretical treatment a step further and
evaluate spectrocopic constants to calculate “ab initio REMPI
spectra” for comparison with the experimental data[24].
C. Research methodology, time plan and milestones. C. a)
Research methodology. C.a. 1) Quantitative, qualitative and energy
resolved analysis of radicals and ions formed by laser multiphoton
absorption. i) High resolution REMPI-TOF measurements (see figure
6): Resonance enhanced multiphoton ionization (REMPI) of jet cooled
gas is performed. Ions are directed into a time-of-flight tube and
detected by a MCP detector to record the ion yield as a function of
mass and laser radiation wavenumber to obtain two-dimensional REMPI
(2D-REMPI) data. REMPI-TOF measurements in more detail: Tunable
excitation radiation is generated using a Lambda Physik COMPex 205
Excimer laser, either with a Lumonics Hyperdye 300 or a Coherent
ScanMatePro dye laser. Relevant dyes are used and frequency
doubling obtained with BBO crystals. The repetition rate is
typically 5 or 10 Hz. The bandwidth of the dye laser beam is about
0.05 – 0.10 cm-1 Typical laser intensity used is 0.2 mJ/pulse. The
radiation is focused into an ionization chamber on a molecular beam
between a repeller and extractor plates. Gas samples are pumped
through a pulsed nozzle into the ionization chamber. Ions are
extracted into a time-of-flight tube and focused onto a MCP
detector, which signal is fed into a LeCroy 9310A, 400 MHz storage
oscilloscope as a function of flight time. Average signal levels
are evaluated and recorded for a fixed number of laser pulses to
obtain mass spectra. The power dependence of the ion signal are
determined by integrating the mass signals repeatedly and averaging
over large number of laser pulses for different laser power.
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9
outoutout
Voltagedevider
HV-2Kv
HX nozzle
TurboPump
TOF
lense
MCP/iondetector
oscilloscope
computer
Excimer Laser
Inout
Dye-Laser
SHG
Timedelay
laser control
Pellin Brocaprism
SHG controlInInIn
REMPI-TOF
Laser beam
Figure 6. REMPI-TOF equipment.
ii) High resolution REMPI-current measurements (see figure 7):
Procedure resembles that described above for REMPI-TOF measurements
except instead of the use of a ionization chamber and a TOF mass
spectrometer a static cell with gas samples at room temperature and
low gas pressure is used. Ionization by means of laser pulses
occurs between electrodes. Voltage drops across the electrodes are
recorded as a function of absorbed photon energy to get 1D- REMPI
spectra. REMPI-current measurements in more detail: Laser radiation
is focused into an ionization cell between two stainless steel
electrodes for recording REMPI-Current spectra. The electrodes are
typically held at ± 200 - 300 voltages. The cell contains gas
samples at low pressure, typically 1 - 5 Torr and room temperature.
Current pulses in the gas due to laser pulse photoionization cause
voltage drops across the electrodes. After amplification and
integration the voltage pulses are fed into a LeCroy 9310A, 400MHz
storage oscilloscope. Finally average voltage values for a fixed
sampling time are recorded as a function of absorbed photon energy
to get one-dimensional REMPI (1D-REMPI) spectra. Typically spectral
points are obtained by averaging over 100 laser pulses.
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+
-
LASER beamLASER beam Figure 7. Schematic diagram for
REMPI-current measurements.
C.a.2) Data from A(see above) are analyzed by use of simulation
models developed within the research group at University of
Iceland.
2D-REMPI-TOF data, such as shown below (Figure 8) for the HCl
molecule, will be analyzed by simulation models to determine
energy-properties of relevant excited states, coupling strengths
between states and contributions of intermediate state to ion
products[24], when relevant. These information form the basis for
determining photorupture channels and photorupture mechanisms.
82833,6
82838,768
82842,88
82846,82857
82850,68
0,72
3624
1
1,32
098
33,1
081
34,8
49
36,6
345
38,4
646
40,3
393
-29967-28540-27113-25686-24259-22832-21405-19978-18551-17124-15697-14270-12843-11416-9989-8562-7135-5708-4281-2854-14270142728544281570871358562998911416128431427015697
2xhv
Mw /amu
35Cl+
37Cl+
H37Cl+
H35Cl+
H+
/cm-1
Figure 8. 2D-REMPI data for HCl
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C.a.3) Tracking Photorupture paths 1) by femtosecond laser
spectroscopy at Bergen University and 2) by kinetic energy
measurements of fragments in Germany.
i) femtosecond laser spectroscopy studies at Bergen University.
Recently facility to perform femtosecond laser spectroscopy studies
has been built within the physics department at Bergen University.
The main device for the new laboratory is a state-of-the-art
titanium sapphire tunable femtosecond laser from Coherent tunable
in the visible and near Infrared spectral region. Furthermore, the
laboratory holds a Nd:Yag pumped Dye laser system suitable to
create nanosecond laser pulses in the visible region. These
equipments are coupled to a gas sample holder and a field
ionization detector suitable to measure high energy Rydberg states
of atoms an molecules. The laboratory is headed by professor Öyvind
Frette (femtosecond studies, optics[50] and experience in studies
of ozone depletion[51]), Dr. Erik Horsdal Pedersen (field
ionization studies and expert in analysis of Rydberg states of
atoms[52]) and professor Jan Petter Hansen (head of physics dept.;
research field: theoretical atom and molecular physics[53, 54]).
These equipments as well as facility to perform laser frequency
doubling will form the basis for our studies of photorupture
channels by femtosecond spectroscopy. See more detailed description
in the frame below. The basic principle of our experiment can by
explained by reference to photorupture processes which are known to
exist for acetylene[36]. See Figure 9:
Orka
HCCH:
HCCH*:HCCH*:C2 CH2C CH2C
H2
Stepwise photoexcitationby a ns laser pulse anda fs laser
pulse
Excitation to Rydberg statesby fs laser pulses followed byfield
ionization
C2C+
*CH2
+
Excitation to Rydberg states by fs laserpulses followed byfield
ionization
Figure 9 Schematic Photorupture studies of acetylene by
femtosecond laser spectroscopy
Initially, acetylene (HCCH) will be excited to a long-lived
electronically excited state (HCCH*) by a ns laser pulse followed
by a fs laser pulse excitation to a dissociative
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electronically excited state (HCCH**). Deformed molecular
species (such as CCH2 or cis-C2H2; see figure 9) and/or fragments
formed by dissociation (such as C2, H2, C and CH2 ; see figure 9)
will be excited by delayed fs pulses to high energy (Rydberg)
states followed by field ionization detection.
Photorupture studies by femtosecond laser spectroscopy in more
detail: HCl as an example
180x103
160
140
120
100
80
E [c
m-1
]
4321r [Å]
H + Cl*(4P)
H + Cl*(2P)
H* + Cl
H + Cl+
H+ + ClX(HCl
+)2Π
HCl**
F(HCl*)1∆ V(H+Cl
-)1Σ
H + Cl*
ns laser pulse excitation
fs laser pulse excitation
field ionization
fs delayed laser pulse excitation
HCl*(Ry) (Ry)
Figure 10. Energetic for HCl relevant to femtosecond studies of
photorupture channels.
HCl gas will be ejected into a gas sample chamber. HCl molecules
will be excited to the F1∆, v´= 0 Rydberg state by two-photon
excitation using frequency doubled nanosecond pulses from a Nd:Yag
pumped Dye laser. F1∆, v´= 0, Rydberg state molecules will be
excited by femtosecond laser pulses in the visible or near infrared
region to a highly excited Rydberg state, which is known to couple
to the V1Σ+ ion-pair state, hence to cause the molecule to transfer
to the ion-pair state and to cause the atoms to move apart. This
process will be followed by two-photon excitations of the
HCl*(Ry)/H+Cl- (ion-pair) species to a highly excited repulsive
HCl** state to form Cl* which can be detected by field ionization.
Furthermore, disappearance of the HCl*(Ry) species can be followed
by field ionization detection of those species with time delayed
field ionization pulses. ii) Kinetic energy measurements of
fragments in Germany. The research group at the Technische
Universitat Braunschweig in Germany headed by prof. Christof Maul
uses REMPI/TOF delay-line detectors (DLD) equipment (see figure 11
and ref. [43]) to record 3D images of ion intensities as a function
of distances from the center of a microchannel plate (MCP) /ion
detector in the time of flight (TOF) mass spectrometer. This allows
derivations of kinetic energies for ions formed by photorupture
channels. Such data (see figure 12) along with the above mentioned
experimental data are very important to characterize photorupture
channels in detail.
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Figure 11. A schematic REMPI/TOF/DLD 3D imaging experimental
setup at Technische Universitat Braunschweig. (see ref. [43] )
H+ kinetic energy
H+
inte
nsity
Figure 12. Proton image following (2+n) REMPI of HCl using the
REMPI/TOF/DLD 3D imaging technique (from ref. [28] )
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14
Photorupture studies by kinetic energy measurements of fragments
in Germany in more detail; HCl as an example: The first project to
be performed along these lines in collaboration with prof. C. Mauls
research group at the Technische Universitat Braunschweig is based
on our observations made for photorupture channels via excitations
to the F1∆, v´= 1 states[24]. Rotational quantum level, J´=8 in
F1∆, v´= 1 is found to couple strongly to the V1Σ+, v´=14, J´=8
state whereas insignificant coupling is observed for other J´
states. This shows as dramatic difference in ion product species
formations. The REMPI/TOF/DLD 3D imaging equipment at Braunschweig
(see figure 11, above) will be used to derive kinetic energy data
for the ion species H+, Cl+ and HCl+ for two-photon excitations to
different J´ levels in F1∆, v´= 1. The data will be used to derive
quantitative and qualitative information relevant to photorupture
channels following interaction between the F1∆ Rydberg state and
the V1Σ+ ion-pair state.
C.a.4) Ab initio spectroscopic parameters and REMPI spectra:
Ab initio calculations at several levels with a number of basis
sets will be performed to study the potential energy surfaces
belonging to Rydberg states of small molecules relevant to the
above mentioned studies. The vibrational and the rotational
spectroscopic parameters can be evaluated by solving the nuclear
Schrödinger equation on a fit potential surface based on ab initio
energies with numerical methods, e.g. the Fourier Grid
Hamiltonian[55]. Based on the calculated spectroscopic paremeters,
the theoretical two-photon absorption spectra can be calculated.
This approach serves the double purpose of helping with the
interpretation of experimental photorupture data as mentioned above
and to act as a guiding tool for making plans about experiments.
This work will be headed by Dr. Andras Bodi at the Paul Scherrer
Institut, Villigen in Switzerland and professor Ingvar Árnason,
University of Iceland [56-59]. Recently, we published a paper
including our first attempt to calculate spectroscopic parameters
and ab initio REMPI spectra for HCl[24]. Slight but significant
improvements in the calculations compared to older calculations[49]
were obtained. Our major contribution in this work was to take the
theory to the next level, and directly compare experimental results
with theoretical predictions. In doing so, we have employed
single-reference methods to calculate excitation energies, e.g.
equation-of-motion coupled cluster singles and doubles[60] or a
renormalized, CR-EOM-CCSD(T)[61] approach. These “out-of-the-box”
methods were able to deliver slightly better results than previous
multireference calculations[49]. However, in order to come close to
experimental accuracy for simple systems, or to make reliable
predictions for more complex ones, a multireference (MR) approach
is needed in order to describe static electron correlation effects,
such as MR-CI[62, 63] or MR-CC[64]. Additionally, explicit
consideration of relativistic corrections and spin-orbit
coupling[65] may also be necessary to reach the desired accuracy.
Ab initio REMPI spectra calculations in more detail: Calculating
Rydberg potential energy surfaces (PES) has two aims. First, the
excitation energy and the rotational constants are known from
experiment. By comparing these with the calculated results, the
methods and basis sets are actually benchmarked. Second, if
computational methods are found that reproduce the experiment
reasonably well, it is worthwhile to try modeling the ensuing
photodissociation-photoionization processes with them. Single
reference coupled cluster methods (EOM-CC and CR-CC) are being used
in our group to study the potential energy surfaces belonging to
Rydberg states of small molecules. Correlation-consistent
Dunning-type basis sets are used (aug-cc-pVXZ, X=T,Q,5...) in order
to be able to systematically improve the wavefunction
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15
flexibility. Nevertheless, these basis sets are occasionally
further augmented with diffuse functions to improve their quality
in the Rydberg space. Test calculations are also carried out with
time-dependent DFT (TDFT). The program packages employed are
Gaussian03 (TDFT), ACES-II (EOM-CC), and/or NWChem (EOM-CC, CR-CC).
By using the NorduGrid network, which HI has recently acquired, the
plan is also to perform multi-reference calculations (MR-CI) using
the program package Molpro. Following either Morse potential or
spline fits to the ab initioPES average internuclear distances (re
/ Å), dissociation energies (De / cm
-1), vibrational frequencies (ωe / cm-1), anharmonicity
parameters (ωexe / cm-1) and the rotational parameter Be (cm
-1) are determined. These parameters coupled with quantum
theoretical formalism for multiphoton transition strengths[66]
allow ab initio REMPI spectra to be predicted.
C.b) Project plan: Research work along the lines as described
above (A-D) will be performed for four major groups of chemical
compounds:
I. Hydrogen halides, HX; X = Cl, Br, I II. Halogens, X2; X = Cl,
I III. Small organic compounds, CxHy IV. Small chlorine containing
organic compounds, CxHyCl as:
chemicals: Project:
Hydrogen halides/ HX; X = Cl, Br, I
Halogens / X2; X = Cl, I
Organic compounds / CxHy
Chlorine containing organic compounds / CxHyCl
A/ REMPI experiments
X= Cl, Br, I
(2+n) & (3+m) REMPI 1)
X = Cl, I; (3+m) REMPI2)
CH4;C2H6 C2H4; (2+n) REMPI3)
CH3Cl; (2+n) REMPI3)
B/ REMPI analysis and simulations
Simulations, photorupture analysis
Simulations photorupture analysis
photorupture analysis
photorupture analysis
C. 1) Femtosecond spectroscopy, 2) kinetic energy
measurements
X=Cl C2H2
D/ ab initio calculations
X=Cl X=Cl CH4
1) Both two- and three-photon resonance enhanced excitations /
i.e. (2+n) and (3+m)
REMPI. 2) Emphasis laid on three-photon resonance enhanced
excitations (i.e. (3+m)REMPI)
which has very limited been performed for the halogens. 3)
Emphasis laid on two-photon resonance enhanced excitations (i.e.
(2+n)REMPI).
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C.c) Time plan and project emphasis:
2009 2010 2011 Weight/ % 1)
A / REMPI measurements HX X2 CxHy CH3Cl 25
B / REMPI analysis HX X2 CxHy 30
C / 1) femtosecond spectroscopy2) Kinetic energy analysis
HCl CH4 /C2H2 15
D / ab initio calculations HCl CH4 / C2H2 15
E / presentations (publications etc.)
HX X2 15
yearProjects:
CH4
CH4
CxHy
1) only to be viewed as a rough estimate for manpower in the
project
D. Co-operation (foreign and domestic) and collaborators
contributions:
Collabor-ators:
A/ REMPI measure-ments
B/ REMPI analysis
C 1./ fs- spectro-scopy
C 2./ kinetic energy exp.
D / ab initio calculat-ions
E / present-ations; publ-ications
In Iceland: Victor Huasheng Wang; Research scientist, U.I.
Leading experiments, student advisor and performs
experiments
Simulations and data analysis
Scientific paper writing, conference presentations
Kristján Matthíasson, PhD student, U.I.
student advisor, performs experiments
Simulations, data analysis and detailed interpretat-ions;
student advisor
Experimental work and analysis
Scientific paper writing, conference presentations, PhD
Thesis
Arnar Hafliðason, MS student, U.I.
performs experiments
Simulations and data analysis
Experimental work and analysis
Data analysis
conference presentations; Thesis, contributions to scientific
paper writing.
Andreas Piekarczyk, ERASMUS /undergradute student from Freiburg,
Germany
performs experiments under supervision
Simulations and data analysis under supervision
BS thesis
Ingvar Árnason, professor in chemistry U.I.
Consultation and student advisor
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17
Collabor-ators:
A/ REMPI measure-ments
B/ REMPI analysis
C 1./ fs- spectro-scopy
C 2./ kinetic energy exp.
D / ab initio calculat-ions
E / present-ations; publ-ications
abroad: Frette Øyvind 1), Professor, Dept. of Physics,
University of Bergen
Leading experiments, student advisor and performs
experiments
Scientific paper writing, conference presentations
Erik Horsdal2), lektor, Dept. of Physics, University of Aarhus
and Bergen
Leading experiments, student advisor and performs
experiments
Scientific paper writing, conference presentations
Jan Petter Hansen3), professor, Dept. of Physics, University of
Bergen
Scientific paper writing, conference presentations
Christof Maul, professor, Technische Universitat Braunschweig,
Germany
Leading experiments, student advisor and performs
experiments
Scientific paper writing, conference presentations
Andras Bodi, postdoctor, Paul Scherrer Institut, Villigen,
Switzerland4)
Consultation, student advisor and performs calculations
Scientific paper writing, conference presentations
1) Öyvind Frette: femtosecond studies, optics[50] and experience
in studies of ozone
depletion[51]. 2) Dr. Erik Horsdal Pedersen: field ionization
studies and expert in analysis of Rydberg
states of atoms[52] 3) Jan Petter Hansen: head of physics dept.;
research field: theoretical atom and
molecular physics[53, 54] 4) Aims to move to Iceland in 2009,
temporarily(?)
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18
E. Gradute student contributions (partly repeted above).
D-E. Estimated contributions in terms of manpower / man-month
(mm) input (see also “C. Detailed budget and justification of cost
for the duration of the project.”)
Students: A/ REMPI measurements
B/ REMPI analysis
C 1./ fs- spectro-scopy
C 2./ kinetic energy exp.
D / ab initio calculat-ions
E / present-ations; publ-ications
Kristján Matthíasson, PhD student, U.I.
student advisor and performs experiments
Simulations, data analysis and detailed interpretat-ions;
student advisor
Experimental work and analysis
Scientific paper writing, conference presentations, PhD
Thesis
Arnar Hafliðason, MS student, U.I.
performs experiments
Simulations and data analysis
Experimental work and analysis
Data analysis conference presentations; Thesis, contributions to
scientific paper writing.
N1.N1., PhD student, U.I.
student advisor and performs experiments
Simulations, data analysis and detailed interpretat-ions;
student advisor
Experimental work and analysis
performs calculations
Scientific paper writing, conference presentations; PhD
Thesis
N2.N2., MS student, U.I.
performs experiments
Simulations and data analysis
Experimental work and analysis
performs calculations
conference presentations; MS Thesis, contributions to scientific
paper writing.
Year: 2009 2010 2011
Particiants: Months work
Months work
Months work
mm mm mm Victor H. Wang 10 10 10 Kristján Matthíasson(PhD) 10 0
0 Arnar Hafliðason (MS) 7 10 5 N1.N1. (PhD) 4 10 10 N2.N2.(MS) 0 4
10 Ingvar Helgi Árnason, prof. U.I. 0.5 0.5 0.5 Frette Øyvind 0.3
0.5 0.5 Erik Horsdal Pedersen 0.3 0.5 0.5 Jan Petter Hansen 0 0.2
0.2 Christof Maul 0.3 0.3 0.3 Andras Bode 2 2 2 Ágúst Kvaran 3 3 3
Total mm 37.4 41 42
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19
F. Proposed deliverables and impacts. Various deliverables are
to be expected as a result of the project. 1. Knowledge-related
benefits of the project: The project will result in additional
basic knowledge relevant to photorupture processes within molecules
for compounds of importance in fields of a) -atmospheric
photochemistry, b) – photoproduction processes of organic molecules
in interstellar space and c) – photosynthesis. Such deliverables
are according to the ideology of basic academic research, such as
“In order to be able to make maximum use of material properties for
applied purposes a complete understanding of its nature is vital.”
2. Environmental benefits: The project deals to large extend with
studies of photorupture processes in small gaseous chlorine
containing reagents which are of importance in the photochemistry
of the atmosphere and ozone depletion. Hence, results from the
project will add to our knowledge of environmentally important
processes in the atmosphere. Various impacts of the research
projects are to be expected, such as:
1) Scientific papers: the three years research project, as
planned, is expected to result in scientific publications in
international journals (say 3 to 5 papers) based on previous
experience. Emphasis will be laid on publications in highly cited
(high impact factor) journals.
2) Academic degrees: According to the plan, significant amount
of the scientific work for the three years project will be
performed by students aiming for academic degrees (MS and PhD). 2
to 4 academic degrees are to be expected.
3) Thesis: The work performed by the students aiming for
academic degrees will result in thesis including mored eitailed
results than to be found in scientific publications. Smaller
subprojects carried out by undergraduates also will result in
thesis.
4) New or improved methodology: The project involves use of a
experimental technique different from that used by others, i.e. use
of mass spectrometer analysis of ions formed by multiphoton
absorption and simulation analysis developed in Iceland in order to
study photorupture processes in molecules. Hence the project will
result in new and improved methodology.
5) A varification of a scientific statement: A statement has
been made that mass spectrometer analysis following multiphoton
ionization as a function of excitation energy coupled with use of
quantum chemical simulation analysis techniques can be use to
identify and quantify photorupture channels in molecules. This
waits to be approved.
6) Simulation model and relevant computer program: The project
involves development of models and relevant computer programs for
simulating data obtained from resonance enhanced multiphoton
ionization data.
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20
G. Proposed publications of results: As clearly seen by the
applicants presentation- and publication- lists emphasis has been
laid on oral and written presentations of research results in the
past. This will continue:
1. Papers will be published in international scientific
journals. Emphasis will be laid on publications in highly cited
(high impact factor) journals. Our first results on photorupture
channels already have been / will be publish in Chem. Phys.
Lett.[36] and J. Chem. Phys.[24] , 2008.
2. Oral presentations will be given at international and
domestic conferences. 3. Written presentations will be published at
conference proceedings, when
relevant. 4. Abstracts, relevant to presentations at conferences
will be distributed. 5. Poster presentations will be given at
international conferences. 6. Oral presentations will be given at
research institutes. 7. Useful thesis writing and clear
presentations by students will be emphasized. 8. Public
presentations about research emphasizes and methodology will be
given. References: 1. Solomon, S., Stratospheric ozone
depletion: A review of concepts and history.
Reviews of Geophysics, 1999. 37(3): p. 275-316. 2. Kvaran, Á.,
Er ey›ing ósonlagsins af völdum efnahvarfa? Náttúrufræ›ingurinn,
1991.
60: p. 127-134. 3. Basic chemistry of ozone depletion;
http://www.nas.nasa.gov/About/Education/Ozone/chemistry.html.
2007. 4. Huasheng, W., et al., Rotationally resolved (2+1) REMPI
spectra of gerade Rydberg
states of molecular iodine: The (v´=0,v´´=1) band of the Dalby
system. J. Mol. Struct., 1993. 293: p. 217-222.
5. Kaur, D., et al., Ion-pair (X++Y-) Formation from
Photodissociation of the Interhalogen Molecules BrCl,ICl and IBr.
Organic Mass Spectrometry, 1993. 28: p. 327-334.
6. Yencha, A.J., et al., Ion-pair formation in the
photodissociation of HCl and DCl. J.Chem. Phys., 1993. 99(7): p.
4986-4992.
7. Kvaran, Á., H. Wang, and J. Ásgeirsson, The Dalby System of
Iodine Revisited: Rotationally Resolved (2+1) REMPI Spectra of the
Rydberg State [2Π1/2] c6s;1g of I2. J. Mol. Spectrosc., 1994. 163:
p. 541-558.
8. Kvaran, Á., et al., REMPI spectra of I2: the [2Π3/2] c5d;1g
Rydberg state and
interactions with ion-pair states. Chem. Phys. Letters, 1994.
222: p. 436-442. 9. Yencha, A.J., et al., Threshold Photoelectron
Spectroscopy of Cl2 and Br2 up to 35 eV.
J. Phys. Chem., 1995. 99: p. 7231-7241.
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21
10. Kvaran, Á., H. Wang, and G.H. Jóhannesson, REMPI spectra of
IBr: Vibrational and rotational analysis of the b[2Π1/2] c6s;1
Rydberg states of I79Br and I81Br. J.Phys.Chem., 1995. 99(13): p.
4451-4457.
11. Jóhannesson, G.H., H. Wang, and Á. Kvaran, REMPI Spectra of
Cl2: Vibrational and Rotational Analysis of the 21Πg Rydberg State
of 35Cl2, 35Cl37Cl, and 37Cl2. J. Molecular Spectroscopy, 1996.
179: p. 334-341.
12. Kvaran, Á., G.H. Jóhannesson, and H. Wang, Rotational
perturbations in the (2+1) REMPI spectrum of the Rydberg state
[2Π3/2] c5d;1g of I2. Chem. Physics, 1996. 204: p. 65-75.
13. Kvaran, Á., H. Wang, and Á. Logadóttir, Rotational REMPI
Spectroscopy; Halogen containing Compounds, in Recent Res. Devel.
in Physical Chem. 1998, Transworld Research Network. p.
233-244.
14. Kvaran, Á., Á. Logadóttir, and H. Wang, (2+1) REMPI spectra
of Ω = 0 states of the hydrogen halides; Spectroscopy,
Perturbations and Excitation Mechanisms. J. Chem. Phys., 1998.
109(14): p. 5856-5867.
15. Kvaran, Á., B.G. Waage, and H. Wang, What to see and what
not to see in 3 photon absorption: (3+1)REMPI of HBr. J. Chem.
Phys., 2000. 113(5): p. 1755-1761.
16. Kvaran, Á., H. Wang, and Á. Logadóttir, Resonance enhanced
multiphoton ionization of the hydrogen halides; Rotational
structure and anomalies in Rydberg and ion-pair states of HCl and
HBr. J. Chem. Phys., 2000. 112(24): p. 10811-10820.
17. Kvaran, Á., H. Wang, and B.G. Waage, Three- and two-photon
absorption spectroscopy: REMPI of HCl and HBr. Can. J. Physics,
2001. 79: p. 197-210.
18. Wang, H. and Á. Kvaran, Three-photon absorption
spectroscopy: (3+1)REMPI of HCl (I1∆(2)-X1Σ(0+)). J. of Molec.
Structure, 2001. 563-564: p. 235-239.
19. Kvaran, Á. and H. Wang, Three-photon Absorption
Spectroscopy: The L(1Φ3) and m(3Π1) States of HCl and DCl. Molec.
Phys., 2002. 100(22): p. 3513-3519.
20. Kvaran, Á. and H. Wang, Three- and two- photon absorption in
HCl and DCl: identification of Ω = 3 states and state interaction
analysis. J. Mol. Spectrosc., 2004. 228(1): p. 143-151.
21. Kvaran, Á., K. Matthíasson, and H. Wang, Three-Photon
Absorption Of Open Shell Structured Molecules; (3+1) REMPI of NO As
A Case Study. Physical Chemistry; An Indian Journal, 2006. 1(1): p.
11-25.
22. Kvaran, Á., Ó.F. Sigurbjörnsson, and H. Wang, REMPI-TOF
studies of the HF dimer. J. Mol. Struct., 2006. 790: p. 27-30.
23. Wang, H. and Á. Kvaran, REMPI spectra of the hydrogen
halides. Acta Physico-Chimica Sinica;
http://www.whxb.pku.edu.cn/en/zxly.asp 2007.
24. Kvaran, Á., et al., Two Dimensional (2+n) Resonance Enhanced
MultiPhoton Ionization of HCl: Photorupture Channels via the F 1D2
Rydberg State and ab initio Spectra J. Chem. Phys. (accepted for
publication), 2008. 129(17): p.?
25. Chichinin, A.I., C. Maul, and K.H. Gericke, Photoionization
and photodissociation of HCl(B 1Σ+, J=0) near 236 and 239 nm using
three-dimensional ion imaging. J. Chem. Phys., 2006. 124(22): p.
224324.
26. Chichinin, A.I., et al., Intermediate state polarization in
multiphoton ionization of HCl. J. Chem. Phys., 2006. 125(3): p.
034310.
27. Romanescu, C. and H.P. Loock, Photoelectron imaging
following 2+1 multiphoton excitation of HBr. Physical Chemistry
Chemical Physics, 2006. 8(25): p. 2940-2949.
28. Romanescu, C. and H.P. Loock, Proton formation in 2+1
resonance enhanced multiphoton excitation of HCl and HBr via (Ω=0)
Rydberg and ion-pair states. J. Chem. Phys., 2007. 127(12): p.
124304.
-
22
29. Romanescu, C., et al., Superexcited state reconstruction of
HCl using photoelectron and photoion imaging. J. Chem. Phys, 2004.
120(2): p. 767-777.
30. Lunine, J.I., Astrobiology. 2005: Pearson; Addison Wesley.
31. Shaw, A.M., Astrochemistry; From Astronomy to Astrobiology.
2006: Wiley. 32. Nummelin, A., Observations of interstellar
molecules:
http://www.chl.chalmers.se/~numa/astrophysics/molecules/molecules.html.
2007. 33. Boye, S., et al., Visible emission from the vibrationally
hot C2H radical following
vacuum-ultraviolet photolysis of acetylene: Experiment and
theory. J Chem. Phys, 2002. 116(20): p. 8843-8855.
34. Campos, A., et al., The 5s-4d Rydberg states of C2H2 and
C2D2 studied by resonant multiphoton ionization and synchrotron
radiation: Structure and stability. J. Phys. Chem., 2001. 105: p.
9104-9110.
35. Shafizadeh, N., et al., Spectroscopy and dynamics of the
Rydberg states of C2H2 and their relevance to astrophysical
photochemistry. Philosophical Transactions of the Royal Society of
London Series a-Mathematical Physical and Engineering Sciences,
1997. 355(1729): p. 1637-1656.
36. Matthiasson, K., H.S. Wang, and A. Kvaran, (2+n) REMPI of
acetylene: Gerade Rydberg states and photorupture channels.
Chemical Physics Letters, 2008. 458(1-3): p. 58-63.
37. Mallory, F.B. and C.W. Mallory, Photocyclization of
stilbenes and related molecules. Organic reactions. Vol. 30. 1988:
Robert E. Krieger Publishing company. 456.
38. Waldeck, D.H., Photoisomerization Dynamics of Stilbenes.
Chem. Rev., 1991. 91: p. 415-436.
39. Evans, C., et al., Photochemistry of Substituted Methyl
a-Arylcinnamates: Ortho and Para- Substitution. J.
Photochem.Photobiol.A:Chem., 1998. 115: p. 57-61.
40. Evans, C., et al., Laser photoisomerization of methyl
α-arylcinnamates; effect of chloro substitution. J.
Photochem.Photobiol.A:Chem.,, 1993. 73: p. 179-185.
41. Zewail, A.H., The Birth of Molecules. Scientific American,
1990(Dec.): p. 40-46. 42. Zewail, A.H., Femtochemistry:
Atomic-scale dynamics of the chemical bond. Journal
of Physical Chemistry A, 2000. 104(24): p. 5660-5694. 43.
Einfeld, T., et al., Photodissociation dynamics of phosgene: New
observations by
applying a three-dimensional imaging technique. Journal of
Chemical Physics, 2002. 116(7): p. 2803-2810.
44. Einfeld, T.S., et al., Photodissociation of CSCl2 at 235 nm:
Kinetic energy distributions and branching ratios of Cl atoms and
CSCl radicals. Journal of Chemical Physics, 2002. 117(3): p.
1123-1129.
45. Einfeld, T.S., et al., Competing dissociation channels in
the photolysis of S2Cl2 at 235 nm. Journal of Chemical Physics,
2002. 117(9): p. 4214-4219.
46. Dunning, T.H., A road map for the calculation of molecular
binding energies. Journal of Physical Chemistry A, 2000. 104(40):
p. 9062-9080.
47. Gwaltney, S.R., M. Nooijen, and R.J. Bartlett, Simplified
methods for equation-of-motion coupled-cluster excited state
calculations. Chem. Phys. Lett., 1996. 248(3-4): p. 189-198.
48. Bettendorff, M., et al., Abinitio Cl Calculation of the
Effects of Rydberg-Valence Mixing in the Electronic-Spectrum of the
Hf Molecule. Zeitschrift Fur Physik a-Hadrons and Nuclei, 1982.
304(2): p. 125-135.
49. Bettendorff, M., S.D. Peyerimhoff, and R.J. Buenker,
Clarification of the assignment of the Electronic Spectrum of
Hydrogen Chloride based on ab initio CI calculations. Chem. Phys.,
1982. 66: p. 261-279.
-
23
50. Jain, M., et al., Effects of aperture size on focusing of
electromagnetic waves into a biaxial crystal. Optics
Communications, 2006. 266(2): p. 438-447.
51. Hamre, B., et al., Could stratospheric ozone depletion lead
to enhanced aquatic primary production in the polar regions?
Limnology and Oceanography, 2008. 53(1): p. 332-338.
52. Mogensen, K.S., et al., Coherent Elliptic States in Lithium.
Physical Review A, 1995. 51(5): p. 4038-4047.
53. Forre, M., et al., Molecules in intense xuv pulses: Beyond
the dipole approximation in linearly and circularly polarized
fields. Physical Review A, 2007. 76(3).
54. Saelen, L., et al., Optical control in coupled two-electron
quantum dots. Physical Review Letters, 2008. 1(4).
55. Stare, J. and G.G. Balint-Kurti, Fourier grid Hamiltonian
method for solving the vibrational Schrodinger equation in internal
coordinates: Theory and test applications. Journal of Physical
Chemistry A, 2003. 107(37): p. 7204-7214.
56. Arnason, I., A. Kvaran, and A. Bodi, Comment on "Relative
energies, stereoelectronic interactions, and conformational
interconversion in silacycloalkanes. International Journal of
Quantum Chemistry, 2006. 106(8): p. 1975-1978.
57. Bodi, A., et al., Conformational properties of
1-fluoro-1-silacyclohexane, C5H10SiHF: Gas electron diffraction,
low-temperature NMR, temperature-dependent Raman spectroscopy, and
quantum chemical calculations. Organometallics, 2007. 26(26): p.
6544-6550.
58. Girichev, G.V., et al., Conformations of silicon-containing
rings, Part 6 - Unexpected conformational properties of
1-trifluoromethyl-1-silacyclohexane, C5H10SiHCF3: Gas electron
diffraction, low-temperature NMR spectropic studies, and quantum
chemical calculations. Chemistry-a European Journal, 2007. 13(6):
p. 1776-1783.
59. Arnason, I., G. Thorarinsson, and E. Matern, Conformations
of silicon-containing rings. II a conformational study on
silacyclohexane. Comparison of ab initio (HF, MP2), DFT, and
molecular mechanics calculations. Conformational energy surface of
silacyclohexane. Z. Anorg. Allg. Chem., 2000. 626(4): p.
853-862.
60. Stanton, J.F. and R.J. Bartlett, The equation of motion
coupled-cluster method. A systematic biorthogonal approach to
molecular excitation energies, transition probabilities, and
excited state properties. J. Chem. Phys., 1993. 98: p. 7029.
61. Kowalski, K. and P. Piecuch, New coupled-cluster methods
with singles, doubles, and noniterative triples for high accuracy
calculations of excited electronic states. J. Chem. Phys., 2004.
120: p. 1715.
62. Werner, H.J. and P.J. Knowles, An Efficient Internally
Contracted Multiconfiguration Reference Configuration-Interaction
Method. Journal of Chemical Physics, 1988. 89(9): p. 5803-5814.
63. Knowles, P.J. and H.J. Werner, An Efficient Method for the
Evaluation of Coupling-Coefficients in Configuration-Interaction
Calculations. Chemical Physics Letters, 1988. 145(6): p.
514-522.
64. Kallay, M., P.G. Szalay, and P.R. Surjan, A general
state-selective multireference coupled-cluster algorithm. Journal
of Chemical Physics, 2002. 117(3): p. 980-990.
65. Berning, A., et al., Spin-orbit matrix elements for
internally contracted multireference configuration interaction
wavefunctions. Molecular Physics, 2000. 98(21): p. 1823-1833.
66. Bray, R.G. and R.M. Hochstrasser, Two-photon absorption by
rotating diatomic molecules. Molecular Physics, 1976. 31(4): p.
1199-1211.