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Cusp satellite bands in the spectrum of Cs2 molecule

We report measurements and a theoretical explanation of the cusp-shaped satellite bands in the blue wing of the cesium D2 resonance line which have been observed for the first time. The bands are identified as 1 /sup 3/ Pi /sub g/(2/sub g/,1/sub g/,0/sub g//sup +/,0/sub g//sup -/) from a /sup 3/ Sigma /sub u//sup +/(1/sub u/,0/sub u//sup +/) transitions where the upper state dissociates into the 6 /sup 2/P/sub 3/2/+6 /sup 2/S/sub 1/2/ atomic asymptote. The experiment has been performed using a standard absorption setup, computer controlled data acquisition and computer data processing. We have shown that the peculiar shape of the 1 /sup 3/ Pi /sub g/(0/sub g//sup +/)-a /sup 3/ Sigma /sub u//sup +/(1/sub u/) difference-potential curve is solely responsible for the spectrum containing the cusp-shaped satellite bands. The appearance of these satellite bands has been discussed and explained relating the theory of satellite bands to the catastrophe theory. The shape of the line wing and of the satellite bands have been calculated using the Fourier transform technique. To ensure a more stringent comparison between the experimental and the theoretical spectrum, we have analyzed and compared the derivatives of the measured and the calculated satellite band shape. On the contrary to the customary direct comparison between the measured and the calculated absorption coefficient, the derivative clearly shows all differences and resemblances between satellite band profiles. The degree of coincidence of the experimentally observed and the theoretically calculated satellite band shape can be used as an ultimate check on the assessment of the quality of potential-energy curves involved in the formation of satellite bands.

cusp satellite bands; visible absorption spectra; Fourier transform spectra; satellite band shape; absorption coefficient; potential-energy curves; Cs dimers; predissociation; D2 resonance line; blue wings Cs2

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