Absorption Spectrum of Na and K in Rare-Gas Matrices

Abstract

The absorption spectrum of Na and K in Ar, Kr, and Xe matrices in the region from 2000 to 8000 Å has been studied as a function of temperature and, at 4°K, as a function of concentration. Observations on some spectra of Na in Ne are also included. The first member of the principal series, ${}^2{P}_{\frac{3}{2},\frac{1}{2}}^{\circ }{\leftarrow }^2{S}_{\frac{1}{2}}$ , can be observed in all matrices. Higher members are weak and can, in most matrices, not be assigned. At alkali concentrations≥0.5%, strong additional absorptions are observed which seem to be due to alkali—alkali interaction. Most transitions appear blue shifted and have triplet structure. The spectra are sharp in xenon but become increasingly diffuse in lighter rare‐gas hosts. The line shape indicates fine structure in most absorption features. During the warm‐up, the ²P←²S absorption broadens and shifts to the red. For a given ratio of observation temperature to melting point of host lattice, atomic absorption of the alkali metals seems to have the same linewidth in all of the observed matrices.