Progress in measurements of Progress in measurements of dissociative recombinationdissociative recombination CRP on Atomic and Molecular Data for Plasma ModellingCRP on Atomic and Molecular Data for Plasma Modelling
Mats Larsson
Department of Physics
Stockholm University
Task for Stockholm according Task for Stockholm according to minutes of 2005to minutes of 2005
BeH+ and BeH2+
Problem: The Manne Siegbahn Laboratory reluctant to deal with Be.
Some pointsSome points
The Stockholm group has no national funding for fusion related research
The storage ring CRYRING is still in operation and beam time will be scheduled for the fall of 2007. The decision to shut down the lab was taken 2002, so the damage control has been quite successful!
Beam time during 2008 unclear
ProgressProgress
Experiment on C4D2+
Results on CF2+ and CF3
+
The H3+ and its isotopologues
Development of data base for dissociative recombination
Doubly excited neutral molecule
A2+B
AB+A
A+A+B
+
e-
DR of polyatomic ions
A2B+ + e- (Ee)
For example:
C2H+ + e- C2 + H + 6.60 eV
CH + C + 3.98 eV
C + C + H + 0.43 eV
3 possible DR -
channels
Research programme
What do we measure?:
• Branching fractions of dissociative recombination• Thermal rate constants/Cross sections of dissociative recombination (energy/temperature – dependence)
Which ions do we study?:
- hydrocarbon ions (so far C2H+, C2H2+, C2H3
+, C2H4+, C2D5
+
C3H4+, C3H7
+, C4D9+, C4D2+), CFn+, H3
+
Manne Siegbahn Laboratory
52 meters circumference
ExperimentExperiment
• Long storage time – internal relaxation
• Multi-pass experiment
CRYRING Heavy Ion Storage Ring
electrons
neutrals
ions
Interaction - DR
ions
dipole magnet
SBD
• Electron cooling – well defined beam size
• Ions interact with electrons – dissociative recombination
• Well defined collision energies - velocity matched conditions
• Detect neutral fragments (from DR process)
A2+ + e A + A; no grid
2A
Energy
Pulse height spectrum
A2+ + e A + A; grid with 30% transmission
2A
A
Energy
All fragment from one DR event hit the detector at the same time yield a pulse at an energy corresponding to full beam energy
Gives no information about
how the molecule breaks up
DR Branching DR Branching fractionfraction measurement measurement
C2H++e-
Relate the fragments to different dissociation channels!
C2H++e-
2C
C+H
C
2C+H
DR Branching DR Branching ratioratio measurement measurement
C2H+ + e- C2
+ H
CH + C
C + C + H
e-
γN
βN
αN
T)-2T(1T)-T(10
T)(12TT)-T(10
T)-(1T0T)T(1
TTT
CN
HCN
2CN
H2CN
2
2
2
322
DR Branching DR Branching ratiosratios – Hydrocarbon – Hydrocarbon ionsions
Products Ratio Products Ratio Products Ratio Products Ratio Products Ratio
C2+H 0.43 C2H+H 0.50 C2H2+H 0.29 C2H3+H 0.11 C2D4+D 0.12CH+C 0.39 C2+H2 0.02 C2H+H2 0.06 C2H2+H2 0.06 C2D3+D2 0.00C+C+H 0.18 C2+H+H 0.30 C2H+H+H 0.59 C2H2+H+H 0.66 C2D3+D+D 0.27
CH2+C 0.05 C2+H2+H 0.03 C2H+H2+H 0.10 C2D2+D2+D 0.28CH+CH 0.13 CH3+C 0.01 CH4+C 0.01 C2D2+D+D+D 0.13
CH2+CH 0.03 CH3+CH 0.02 C2D+D2+D2 0.00CH2+CH2 0.04 C2D+D2+D+D 0.00
CD4+CD 0.02CD3+CD2 0.17CD3+C+D2 0.00
C2D5+C2H
+ C2H2+ C2H3
+ C2H4+
Results have been compiled by Janev and Reiter (2002, 2004), and byFlorerscu-Mitchell and Mitchell (2006) and Adams, Poteryaand Babcock (2006)
Viggiano et al. 2005
CF2+ + e CF + F 714
CF3+ + e CF2 + F
8010Ehlerding et al. 2006
New theory: PRL 90, 133201 (2003), PRA 68, 012703 (2003)
CRYRING
2000
Theory
ke[cm3s-1]
2003
AISA
Kreckel et al., Phys. Rev. Lett. 95, 263201 (2005)
TSR
CRYRING
H3+
H3+ D3
+
D2H+ May 2007, CRYRING
-900 V/ring
electrode
H2
para
Gas inlet/2 atm
Solenoid valve
Pinhole flange/ground
electrode
Insulating spacer
Skimmer
Planned experimentPlanned experiment
Ion source will be characterised at the University of Illinois, in Ben McCall’s group with cavity ring-down spectroscopy; critical question: can we produce para-H3
+
using para-H2 as feed gas?
Experiment planned for September 2007, one week of beam time has been allocated
Advanced Intergrated Stationary AfterglowGlosik et al. 2005
Glosik et al. 2005
Summary HSummary H33++
Good agreement experiment-theory for dissociative recombination of H3
+, D3+ and H2D+
Several storage ring experiments agree with each other, but disagree with theory
Stationary afterglow experiments for H3+ give
almost factor 100 lower rate coefficient than storage rings and theory
Para-H3+ will be used in experiment in CRYRING