10min:
OBSERVATION OF THE 5~1 Sigmau+ and 5~1 Piu STATES OF Rb2 BY POLARISATION LABELLING SPECTROSCOPY .

JACEK SZCZEPKOWSKI, ODZIMIERZ JASTRZEBSKI, Institute of Physics, Polish Academy of Sciences, Al. Lotnikóv 32/46, 02-668 Warsaw, Poland ; PAWE\L KOWALCZYK, ANNA GROCHOLA, Institute of Experimental Physics, Department of Physics, University of Warsaw, ul. Hoza 69, 00-681 Warsaw, Poland ; ABDUL-RAHMAN ALLOUCHE, PATRICK CROZET AND AMANDA J. ROSS, Institut Lumière Matière, Université Lyon 1 & CNRS UMR5306, Université de Lyon, France.

Two-colour polarization labeling experiments have been used to explore the excitation spectrum of the rubidium dimer in the region 25500 - 27000 cm-1, aiming to establish the symmetry of excited states observed by Han and Heaven in earlier work. The spectra we recorded in fact probe quite different electronic states; we identify them from ab initio calculations as the 5~1 Sigmau+ and 5~1 Piu states, dissociating to Rb 5s + Rb 5d atoms. The home-made pulsed laser used to label levels in the electronic ground state, with nominal linewidth of 0.3 cm-1, is not sufficiently selective for this heavy-alkali species. The spectra are a tangled confusion of short and rather irregular progressions of P,R doublets and/or Q lines. We have had to use cross-correlation techniques to identify transitions seen in different spectra that share a common ground state level, to establish assignments. Analysis confirms unusual vibrational patterns in the lowest vibrational levels, from avoided crossings with ion pair states.