Laser fluorescence spectroscopy of three‐level systems

In common laser fluorescence spectroscopy a quasi‐instantaneous distribution of the laser‐coupled levels according to their statistical weights is assumed. This saturation case can only be achieved by a fast rising laser pulse of sufficient intensity. Otherwise, losses from the laser‐pumped levels and the time dependence of the laser pulse have to be taken into account. In this paper a model including losses is investigated. Normalized fluorescence curves result which are characterized by one fit parameter. Into this parameter the rise time of the laser pulse, the overlap of the laser line and of the corresponding atomic line and its oscillator strength enter. The influence of the loss processes on the peak of the fluorescence curve can be shown. The model is applied to measurements at a nonthermal neon plasma of a microwave discharge. Transitions from the levels 2p5 3s 3P0, 3P1, 3P2 to a common upper level 2p5 3p 3P1 have been pumped. Evaluation of the fluorescence signal (2p5 3p 3P1→2p5 3s 1P1) leads to...