Imprisonment of Resonance Radiation in a Planar Gas Discharge with Reflecting Walls

The imprisonment time of Doppler-broadened resonance radiation in a planar gas discharge is calculated numerically and compared with the analytic approximation of Walsh. This comparison shows that Walsh's results are higher than the numerical results by as much as 17% for no electronic collisional deexcitation, and by as much as 63% for copious electronic collisional deexcitation (at an optical thickness of 10). In addition, the effect of diffusely reflecting walls on the imprisonment time is calculated numerically and compared with the analytic approximation of Weinstein where possible. The numerical results are rigorously valid in the optically thick limit and approximately valid in the optically thin limit.