Transcript WK03.ppt
Observation of the 5 1Su+ and 51Pu states of Rb2 by polarisation labelling spectroscopy Just two of many excited states lying about 26000 cm-1 above the electronic ground state. Jacek Szczepkowski, Włodzimierz Jastrzebski Institute of Physics, Polish Academy of Sciences, Warsaw Paweł Kowalczyk, Anna Grochola Institute of Experimental Physics, University of Warsaw Abdul- Rahman Allouche, Patrick Crozet and Amanda Ross Institut Lumière Matière, UMR 5306, Université Lyon1 & CNRS Amanda Ross (WK03) PAN-CNRS € Intentions A straightforward project to identify L 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 L', v', (J-1), J, (J+1) Pump (scan) B 1P u Label (fixed wavelength probe) Tuned to chosen B-X transitions "V" scheme X 1Sg+ Amanda Ross (WK03) v", J Polarisation spectroscopy selection rules Label X state v",J" with a fixed laser wavelength (LABEL/PROBE) Scan the other (Pump). Illustration for a 1Pu upper state Label transition Rb2 Pump lasernpolarisation B 1Pu – X 1Sg+ Circular strong P,R Linear strong Q + weak P,R Circular nothing Linear strong Q + weak P,R P(J) or R(J) Q(J) Combinations can confirm assignments. Amanda Ross (WK03) Experiment (IF-PAN) Nile blue, DCM label B-X BBQ + BBD Excellent sensitivity (crossed polarisers + spectrograph) Laser used to 'label' has fwhm 0.25 cm-1. Amanda Ross (WK03) Signals ? Yes. In fact, too many signals! Supposed to show transitions from v"=1 J"=73 Pump laser with circ. polarisation Label via P(73) 7-1 B-X ?? This experiment is NOT selective. The spectra are (very) hard to assign. 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 Both spectra labeled via R(47) 5-1 and R(47) 6-1 (products shown) pump laser circular polarisation cm-1 Amanda Ross (WK03) Quantum number assignments ? J' reasonably secure (from correlated pump transitions) v' Harder, DG and DF intervals not quite regular. Two similar states, 1 + Su 1 1 + u P P u DG ~31.7 cm-1 DG ~35.8(2) cm-1 DG ~35.1(2) cm-1 85Rb 2 & 85Rb87Rb Bv ~0.0158 cm-1 acceptable Bv ~0.0159 cm-1 Bv ~0.0164 cm-1 + observations confirm v for 1Su FCF patterns suggest assignments for 1Pu Amanda Ross (WK03) messy Preliminary results Dunham type parameters, levels v = 2 - 20 1P 1S + u u 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 1Pu and 5 1Su+ Amanda Ross (WK03) RKR curves show how close these states are Remarkably close to ab inito V(R) 5 1Pu Data 5 1Su+ Points : RKR curve. Lines : ab inito (A-R Allouche) Amanda Ross (WK03) The pseudopotential CI theoretical point of view 5p + 5p 5 1 Su + 5s + 6p 4 1 Su + AR Allouche : extension of calculations published in JCP 136, 114302 (2012) Amanda Ross (WK03) Conclusion so far. E cm-1 5 1P u 5 1Su+ 28000 26000 5 10 15 20 R (A) 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 1Pu and 1st well of 4 1Su+ . Amanda Ross (WK03)