Population rate equations modelling of a resonant ionisation process

Abstract

A four level population rate equations model is described and is used to interpret published resonant ionisation data for the Yb atom. Three different laser wavelenghts were used in the experiment for the excitation steps. The ion-yield graphs as a function of laser fluences are well reproduced. From the analysis, the Einstein coefficient for the transition of the 17³P₂ state to the 7³S₁ state is determined to be 9940 s^–1 with an uncertainty of 10%. The sensitivity of multi-photon processes to a time structure in the laser pulse is studied and important differences in ion yield are calculated for excitation steps involving simultaneous absorption of two or more photons.