6S1/2-6P1/2 transition of Cs atoms in cubic and hexagonal solid 4He

We present a systematic experimental study of the absorption and fluorescence spectra of the 6S(1/2)-6P(1/2) transition in Cs atoms isolated in solid He-4 matrices. The bubble model developed earlier for alkali-metal atoms in liquid He is revised and applied to the present system. The analysis of the dependencies of absorption and fluorescence wavelengths on He pressure in liquid and solid He (cubic and hexagonal) environments leads us to modify the bubble model by taking the elastic deformation of solid He by the atomic bubble into account.