Pulsed spontaneous Raman scattering technique for luminous environments

Abstract

A gated photon counting system, cavity-dumped argon-ion laser, and a multipass retroreflecting light cell have been combined in a system to enhance spontaneous Raman scattering in luminous background situations. Signal-to-background ratio (SBR) has been improved a factor of 450 over a single-pass cw system with cw power equal to the pulsed average power. The improvement attributable to the gating and cavity dumping the laser is a factor of 30. A factor of 15 improvement is due to the retroreflecting light cell. Temperature and density data obtained from N₂Q-branch spectra of a luminous methane–air flame are presented to illustrate the utility of the system. A passband fitting technique is introduced to analyze the data.