LASER PHOTOACOUSTIC SPECTRA OF GASEOUS MOLECULES

<正> Photoaeoustic spectroscopy (PAS) has become a valuable technique for detection of weak signals. The photoacoustic effect, on which PAS is based, was discovered as early as 1880 by A. G. Bell, but for a long period afterward, it did not find widespread application. In the 1970s, it was revived primarily because of technological advances made during the preceding two decades. One of these important achievements was the development of laser. Compared to incoherent sources of radiation, laser sources offer an enormous improvement in collimated optical intensity per unit optical bandwidth, so that increased sensitivity may be obtained by the use of lasers as sources of exeitation.