Amanda Ross (WK03) Observation of the 5 1 u + and 5 1 u states of Rb 2 by polarisation labelling spectroscopy Jacek Szczepkowski, Włodzimierz Jastrzebski.

Amanda Ross (WK03)

Observation of the 5 1u+ and 51u states of Rb2

by polarisation labelling spectroscopy

Jacek Szczepkowski, Włodzimierz JastrzebskiInstitute of Physics, Polish Academy of Sciences, Warsaw

Paweł Kowalczyk, Anna GrocholaInstitute of Experimental Physics, University of Warsaw

Abdul- Rahman Allouche, Patrick Crozet and Amanda RossInstitut Lumière Matière, UMR 5306, Université Lyon1 & CNRS

Just two of many excited states lying about 26000 cm-1 above the electronic ground state.

PAN-CNRS€

Amanda Ross (WK03)

Intentions

A straightforward project to identify in electronic states seen by Han & Heaven J Mol Spectrosc. 268 37 (2011).

"Cold" excitation spectrum, vib. resolution, UV accessible with ns dye laser

Amanda Ross (WK03)

Key changes in the experiment heatpipe source ~250 °C

2 colour polarisation labelling spectroscopy

Work at higher J, but selectively

', v', (J-1), J, (J+1)

B 1u

"V" scheme

X 1g+ v", J

Pump (scan)

Label (fixed wavelength probe)Tuned to chosen B-X transitions

Amanda Ross (WK03)

Polarisation spectroscopy selection rules Label X state v",J" with a fixed laser wavelength (LABEL/PROBE)

Scan the other (Pump). Illustration for a 1u upper state

Label transition Rb2

B 1u – X 1g+

P(J) or R(J)

Q(J)

Pump lasernpolarisation

Circular strong P,R Linear strong Q + weak P,R

Circular nothing Linear strong Q + weak P,R

Combinations can confirm assignments.

Amanda Ross (WK03)

Experiment (IF-PAN)

Excellent sensitivity (crossed polarisers + spectrograph)

Laser used to 'label' has fwhm 0.25 cm-1.

Nile blue, DCM label B-X

BBQ + BBD

Amanda Ross (WK03)

Signals ? Yes. In fact, too many signals!

This experiment is NOT selective. The spectra are (very) hard to assign.

Supposed to show transitions from v"=1 J"=73

Pump laser with circ. polarisationLabel via P(73) 7-1 B-X ??

Amanda Ross (WK03)

Record another spectrum . Look for correlations

Amanda Ross (WK03)

Better way to correlate spectra : take products.

Multiply those two spectra. Sacrifice intensity information to some degree

Amanda Ross (WK03)

Iterate until something emerges

pump laser linear polarisation

pump laser circular polarisation

Both spectra labeled via

R(47) 5-1 and R(47) 6-1(products shown)

cm-1

Amanda Ross (WK03)

Quantum number assignments ?

J' reasonably secure (from correlated pump transitions)

v' Harder, G and F intervals not quite regular.

Two similar states,

1u

+ G ~31.7 cm-1 Bv ~0.0158 cm-1 acceptable

1u

+ G ~35.8(2) cm-1 Bv ~0.0159 cm-1 messy

1u

- G ~35.1(2) cm-1 Bv ~0.0164 cm-1

85Rb2 & 85Rb87Rb observations confirm v for 1u

+

FCF patterns suggest assignments for 1u

Amanda Ross (WK03)

Preliminary results Dunham type parameters,

levels v = 2 - 20

1u

1u+

Te 26131.4 26114.2

Y10 35.603 31.76

Y01 0.0159 0.0159

105 Y11 -3.73E-05 -3.874

105 q01 6.37

RMS dev. 0.3 0.1

Compare with ab initio results : likely assignment 5 1u and 5 1u

+

Amanda Ross (WK03)

RKR curves show how close these states are

Remarkably close to ab inito V(R)

5 1u

5 1u+

Points : RKR curve.

Lines : ab inito (A-R Allouche)

Data

Amanda Ross (WK03)

The pseudopotential CI theoretical point of view

AR Allouche : extension of calculations published in JCP 136, 114302 (2012)

4 1u+

5 1u+

5p + 5p

5s + 6p

Amanda Ross (WK03)

Conclusion so far.

1. The interesting parts of V(R) are not yet observed.

2. No progress at all with the original project, but

those states were possibly 4 1u and 1st well of 4 1u+ .

5 1u+

5 1u

E cm-1

28000

26000

5 10 15 20 R (A)