FESHBACH-TYPE ELECTRON RESONANCES IN SOLID AR, KR, AND XE FILMS - DECAY INTO MULTIPHONON EXCITATIONS

We show from high-resolution electron-scattering experiments on multil ayer films of Ar, Kr, and Xe that a core-excited electron resonance, w hich consists of the temporary attachment of an electron to an exciton , exists in the pure solid. It is located at 11.78, 9.70, and 7.85 eV, slightly below the lowest bulk exciton energy of Ar, Kr, and Xe, resp ectively. This resonance, which is more specifically identified as a F eshbach-type resonance, is long lived and decays by releasing a substa ntial amount of energy (0.1-1.0 eV) to the lattice. Its lifetime is es timated from a semiclassical analysis of the multiphonon electron-ener gy-loss data to be the same for all three rare-gas solids and equal to 5.6 x 10(-14) sec.