PHOTO-ACOUSTIC SPECTROSCOPY OF THE V3 BAND OF HCN

All fundamental transition frequencies to the 25 lowest rotational levels of the nu //3 band of HCN have been measured for the first time using a photoacoustic spectrometer consisting of an F-center laser, a photoacoustic absorption cell, and an infrared wavemeter. The 49 transitions were measured at an HCN pressure of only 20 mTorr and an rms deviation of 0. 002 cm** minus **1 from the calculated values. Effects of pressure broadening and pressure shifts were examined. In addition, the techniques of intracavity photoacoustic spectroscopy and frequency-modulated photoacoustic detection have been demonstrated for investigating transitions in this band at low pressure.