Spectroscopy studies of the B/sup 1//spl Pi//sub u/ state of Cs/sub 2/

More than 1000 rovibrational transitions between the first excited B/sup 1//spl Pi//sub u/ state and the ground X /sup 1//spl Sigma//sub g//sup +/ state of Cs/sub 2/ were observed and analyzed. The laser-induced fluorescence of Cs/sub 2/ molecules pumping with a solid-state-pumped single-mode Ti:sapphire laser was detected with an ultra-high resolution monochromator and photomultiplier tube. The high level density and small electronic separation of cesium dimers due primarily to the large dipolar interactions and heavy nuclei comparing with the lighter alkalis make the laser-induced fluorescence unresolvable. The ultra-high resolution monochromator acts as a band pass filter (about 1 cm/sup -1/ line width) and tuned to the favored transition to eliminate the other transitions. From the measured term values, Dumham coefficients, RKR potential of B/sup 1//spl Pi//sub u/ state have been calculated which yield the potential parameters T/sub e/ = 13043.638(5) cm/sup -1/, Re = 4.85 /spl Aring/, D/sub e/ = 2338.5(8) cm/sup -1/, B/sub e/ = 0.01077(1) cm-1, and /spl omega//sub e/ = 34.37(4) cm-1. This is in good agreement with Diemer' s results.