Time-resolved secondary emission from three-level electron-phonon coupled systems: Numerical study of radiative and nonradiative transitions

摘要

The spectral structures of the transient resonant secondary emission are investigated in a three-level electron-phonon coupled system in order to clarify dynamical properties of the nonradiative transitions occurring in the crossing region of the potential-energy curves. The time-resolved resonant secondary-emission spectra are calculated for an instantaneous excitation pulse; in the calculation, we take into account the uncertainty relation between energy and time for emission processes by introducing explicitly a temporal form of the resolution function of the measurement system. The time evolution of the excited state is solved numerically by using the real-time Trotter's formula, without assuming any a priori trajectories. We study how the lattice relaxation and the nonradiative transition contribute to the processes of secondary emissions by analyzing the temporal behaviors of the emission spectra. It is found that, in addition to the peaks due to the radiative transitions from the excited states during the lattice relaxation, the oscillatory structures appear in the spectra in the energy domain, which is due to the quantum-mechanical interference effects of the excited states in the potential crossing region. [References: 12]