Continua in the visible absorption spectrum of k2

The visible absorption spectrum of the potassium dimer has been studied using a new type of optical cell designed specifically for the alkali vapors or alkali-rare-gas mixtures. Particular emphasis has been placed on examining the diffuse K2 bands lying at 722, 575, 478, and 402 nm. Measurements of the reduced absorption coefficient for each feature are presented, and band assignments are made in light of ab initio potential energy-level calculations for K2 that were recently made by Konowalow and Fish [D. D. Konowalow, State University of New York, Binghamton, N.Y. (personal communication)]. All the observed features are attributable to extrema in the difference potentials between various pairs of K2 electronic states. In addition, the 575-nm band includes contributions from free (formula presented) bound (excimer) (formula presented)Hg absorptive transitions of the molecule. Undulatory structure on the short- wavelength side of the 402-nm band has a periodicity of 58 ± 4 cm-1 and is associated with the well-known bound (formula presented) bound (formula presented) transition of K2.