Creation of free excitons in solid krypton investigated by time-resolvedluminescence spectroscopy

Abstract

The creation and relaxation of secondary excitons in solid Kr was investigatedusing energy-and time-resolved luminescence spectroscopy in the vacuumultraviolet region. The spectrally selected emission of the free exciton (FE) wasused as a probe for an investigation of the different exciton creation processes.Delayed FE creation via electron–hole recombination and ‘prompt’ (in terms ofthe time-resolution of the experiment) creation of excitons were separated. The‘prompt’ creation of a FE appears in the region above threshold energyEth,which is equal to the sum of the band gap energy and thefree exciton energy. ‘Prompt’ creation of excitons aboveEth isascribed to a superposition of two processes: (i) creation of the electronic polaroncomplex (one-step process) and (ii) inelastic scattering of photoelectrons describedin the framework of the multiple-parabolic-branch band model (two-step process).In addition, the ratio spectrum of the time-integrated FE and self-trapped exciton(STE) emission was analysed. The behaviour of the ratio spectrum is a proof thatelectron–hole recombination leads to STE states through FE states as precursors.