High-resolution measurement of water-vapor overtone absorption in the visible by frequency-modulation spectroscopy

We demonstrate the use of near-shot-noise-limited frequency-modulation spectroscopy in the study of a weakly absorbing transition of water vapor at 16 940.27 cm−1. The high sensitivity of the technique allows a detailed study of the line shape to yield accurate air-induced pressure-broadening and line-center shift coefficients and the self-induced pressure-broadening coefficient of the transition.