Rotational Absorption and Dispersion of Ultrasonics in Hydrogen

The absorption and dispersion of the velocity of ultrasonic waves when the rotational degrees of freedom fail to follow the acoustic cycle were early predicted by Rayleigh, Jeans, and others. The anomalous absorption in hydrogen was first observed by Abello and carefully investigated by Van Itterbeck and his co‐workers to yield a value of the relaxation time. The dispersion of the velocity was first reported by the authors together with a rough observation of the absorption peak and determinations of the relaxation time. Rhodes and Zartman have reported on more precise and extensive measurements of the dispersion and absorption curves. In this paper new data on these curves and some new developments in the theoretical interpretation of these data will be presented.