Sensitive gas-phase photoacoustic spectrometer with provision for simultaneous recording of absorption spectrum

Abstract

The design of a sensitive pulsed photoacoustic spectrometer system for studying media in gaseous phase in the visible and ultraviolet regions is described. The system provides for simultaneous recording of the laser absorption spectrum of the sample by measuring the radiation transmitted through the sample cell. A highly sensitive optogalvanic detection subassembly for recording the calibration spectrum and analog signal processing/averaging electronics including gated integrators also form part of the system. Typical sensitivities of detection are a few tens of picobar acoustic pressure disturbances induced through two-photon absorption in iodine vapor in the sample cell and 0.1 pC charge fluctuation induced in the neon/uranium hollow cathode discharge through optogalvanic effect. Typical recordings of the photoacoustic, laser absorption, and two-photon photoacoustic spectra of the saturated vapor of iodine at room temperature in the presence of air at atmospheric pressure are presented together with the optogalvanic calibration spectra.