Abstract

Optoacoustic spectroscopy has many advantages in the study of weakly absorbing gases, liquids, and solids. However, to date this capability has not been exploited for obtaining new spectroscopic information on interesting liquids and solids. In this paper I shall review the application of optoacoustic spectroscopy to cryogenic liquids and solids. Among the cryogenic liquid studies, overtone absorption spectra of liquid methane and ethane and those of solid hydrogens (H₂, D₂, and HD) are described in detail because of their importance to scientific understanding as well as to understanding of optical astronomical data of outer giant planets such as Jupiter, Uranus, and Neptune. In solid parahydrogen, I report the first observation of the fourth vibrational overtone (Δv = 5) in the 19,000-cm^-1 region. Further, I describe the measurements of lifetimes of vibrational levels of solid hydrogen. These lifetimes are anomalously short for homonuclear diatomic molecules and provide a risk data for theoretical physics. I conclude by providing a view into the other profitable areas that can be explored through the study of weak absorption spectra.

© 1986 Optical Society of America