Radiation trapping in a stepwise-excitation electron-laser coincidence experiment

The observation of radiation trapping effects in time-resolved, stepwise-excited, electron-photon coincidence signals is reported. Hg atoms were excited by electron impact to the 6 1P1 state and then by laser excitation to the 6 1D2 state. Coincidence signals were observed from the 6 1D26 3P1 (313-nm) transition. The decay time of these signals was found to depend upon radiation trapping of the electron-impact-excited 6 1P16 1S0 (185-nm) resonance line. An explanation of this effect is given in terms of the laser excitation coupling the 313- and 185-nm transitions. © 1991 The American Physical Society.