INTRACAVITY ABSORPTION SPECTROSCOPY

Intracavity Absorption Spectroscopy is a very sensitive means of studying very weak absorption lines. With cw dye lasers, peak absorption coefficients as weak as 10('-8) cm('-1) can be detected in a 50 cm optical path. The apparatus described herein was used to make the first laboratory detection of the extremely weak 3-0 band of the atmospheric bands in ('16)O(,2). The system could maintain this sensitivity at ambient pressures as low as 50 Torr.

With slight modifications to the laser system, the 2-0 band of ('18)O(,2) was measured. From this measurement the first experimental B and D constants of the b('1)(SIGMA)(,g)('+) (v' = 2) state were calculated.

A close examination of the models governing the physics of intracavity absorption was made to determine how to maximize the sensitivity. As a result, an alternate steady-state model was developed. Qualitative agreement was found between experimental results and the model.

Recently, investigators have noticed curious phenomena associated with the spectra obtained by Intracavity Absorption Spectroscopy. Some of these peculiarities were investigated and explanations are offered.

This study has shown that Intracavity Absorption Spectroscopy is a useful spectroscopic tool.