Phonon Relaxation and Resonant X-Ray Emission Spectrum in 1s Core Exciton State of Diamond

Abstract
The phonon relaxation dynamics in the creation of the C Is core exciton in diamond is investigated theoretically by calculating the X-ray absorption and resonant X-ray emission spectra. The C Is core exciton state in diamond strongly couples with the lattice local phonon mode. As a result of this, the excited C atom relaxes to a new equilibrium position lying in the [111] direction. Due to the relatively short lifetime of the core excited state, this off-center displacement is exhibited as the hot luminescence in the resonant X-ray emission çpectrum. Spectral features experimentally obtained by Ma et al. are qualitatively well reproduced by the simple vibronic cluster model.