Absorption by dissociative continua and Rydberg states in condensed matter: HCl in rare gas matrixes

The absorption spectra of HCl in rare gas matrixes were recorded in the 1st continuum (A 1P->X 1S+) region in Kr and Xe matrixes and up to 100 nm in Ar matrixes. Concn. and temp. effects were used to distinguish between absorption from monomers and that from clusters. The 1st continuum band of the monomer is seen to shift red by .apprx.0.36 eV in Ar matrixes, while it shifts blue by .apprx.0.3 and .apprx.0.08 eV in Kr and Xe matrixes, resp. Simultaneously, the oscillator strength of the A 1P state increases drastically in the sequence Ar-Kr-Xe. These trends can be interpreted by the fact that the excited state is solvated in Ar by dispersive and inductive interactions with the environments, while in Kr and Xe matrixes, absorption is dominated by HCl--Rgn+ charge transfer states (Rg = Kr, Xe). At higher energies and in Ar matrixes, discrete absorption by the b 3P, C 1P, H 1S+, K 1P and M 1P states occurs and their relative intensities reproduce well those of the gas phase. However, the b and C states are blue shifted with respect to their gas phase energies by .apprx.0.6 eV, in agreement with their predicted Rydberg character, while the H, K and M states are just slightly red shifted casting some doubt about their classification as Rydberg states. [on SciFinder (R)]