Photo-acoustic spectrometer with Ti:sapphire laser

Abstract

A dual-channel photo-acoustic (PA) spectrometer using a single mode 1 W Ti-Sapphire laser with 50 kHz linewidth is described. The value of minimal detectable absorption coefficient equals of 10 -8 cm -1 was determined from the measurements of water absorption lines with well-known intensities. The PA spectrometer was applied to record weak absorption spectra of water, HDO, SiH 4 , H 2 Se, AsH 3 in 11,300 - 12,800 cm -1 region. The photo-acoustic (PA) method based on the measurements of an optical radiation absorption by the substance under study. When the pulsed optical radiation passes through the cell containing an absorbing substance (molecular gas in our case) the last one heats due to the absorption. The heat of the gas in a closed volume of the PA cell produces the pulse of the pressure (Delta) p, which was detected by a sensitive microphone proportional optical radiation energy W and absorption coefficient of gas k(v).