Dissocn. efficiencies for excitation of the repulsive A 1P state of HCl were recorded in Xe, Kr, and Ar matrixes for photon energies between 5 and 10 eV from the content of dissocn. products and quantum efficiencies were derived with the absorption spectra. Influence of temp. and prepn. conditions was investigated. The quantum efficiency rises monotonically in Xe from an excess energy of 1.4 eV above the gas phase dissocn. energy on, sats. around 2.4 eV and remains then essentially const. up to 4 eV. In Ar and Kr, it sats. around 2 eV and in Ar an abs. efficiency of about 0.18 is detd. at 3.7 eV. Results of mol. dynamics calcns. and a statistical model agree qual. but the obsd. satn. at low excess energies is not well described and the absence of a temp. effect in Ar needs further consideration. [on SciFinder (R)]