PROBE: a new technique for measuring the density profile of a specific constituent using counterpropagating laser pulses

A new approach at attaining density measurements of a specific constituent with spatial resolution using two counterpropagating laser pulses is proposed. This PROBE (Profile Resolution Obtained by Excitation) concept involves exciting the species of interest with one pulse then probing the wake of excited atoms or molecules with a second laser pulse. The lifetime of the excited state, in terms of the time for the laser pulse to cross the region of interest, turns out to be an important parameter in specifying the form of the relation needed to ascertain the profile of the species under investigation. This new technique could find application in several areas, ranging from remote atmospheric pollution monitoring in the ir to trace species profile evaluation within plasma or chemical reactors.