Competition between electronic energy transfer and relaxation in Xe-doped Ar and Ne matrices studied by photoelectron spectroscopy

Abstract

Thin films of solid Ar and Ne doped with 1-at.% Xe were excited with photons in the energy range from 10 to 20 eV in order to measure the energy distribution of the emitted electrons. Binding energies of the host and guest levels are deduced. When host excitons are excited, strong emission of electrons is observed indicating an efficient transfer of the host exciton energy to the Xe guest atoms. The energy of the free excitons is transferred as can be deduced from the kinetic energy of the photoemitted electrons rather than the energy of the bound (self-trapped) excitons which are observed in luminescence experiments. Furthermore, there is a striking difference between the Ar and Ne matrix: In the Ne matrix a fast relaxation from the $n=2$ to the $n=1$ state was observed and only the energy of the $n=1$ exciton is transferred even when higher excitons are excited, in contrast to Ar, where the transferred energy is higher for excitation of the $n=2$ excitons than for $n=1$. From these observations time hierarchies for the competition between electronic energy transfer and relaxation are deduced.