Ultraviolet and visible absorption spectra of potassium and potassium-xenon mixtures

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 nm, 575 nm, 478 nm 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. The 575 nm band is found to arise from the free -bound (excimer) 23rr + 13I:+ transition of the g u molecule, and the band peaking near 722 nm, which has been previously attri13rr 13 + . i h bid buted to t he + I: trans~t on, as een reexam ne • The blue and violet g u features are shown to probably arise from the c1rru + XlI:; transition of K2• The ultraviolet and visible absorption spectra of potassium vapor -xenon 17 -3 mixtures have been studied for [K] and [Xe] as large as 7·10 cm , respectively. Collision-induced absorption is observed in the ultraviolet (285 < gamma < 370 nm) for the 4S + nF, nD (4 < n < 8) transitions as well as for the 4S + 5S transition in the visible, but peak absorption lies an average of ~ 0.6 nm to the red side of the position of the electric dipole forbidden line. The 4S + 4F, 5F transitions, in particular, are quite strong, having peak reduced absorption coefficients measured (within a factor of 2) to 5 cm, respectively. The KXe (C2Sigma) excimer has been observed in absorption for the first time. Absorption at the band peak (reduced absorption coefficient of ~2.10-40 cm5 at gamma = 507 rum) is roughly two orders of magnitude weaker than that for the analogous bands of CsXe and RbXe and is displaced at least 5 rum to the blue side of the peak (~520 rum) in the emission spectrum. Six reproducible undulations to the blue side of the absorption maximum display a periodicity of III ± 17 cm. KXe absorption bands associated with the 3 D 2 and 5 P states of potassium, which were first observed indirectly by Webster and Rostas, have also been examined.U of I OnlyThesi