Absorption Coefficient of Water Vapour in the Far Infra-Red Region

Abstract

In the present paper absorption coefficlent of water vapour in the far infra-red region beyond 5μ was calculated quantun-mechanically by the method of Elsasser. Main points introduced in the present papr are summarised as follows: i). intensity of an absorption line was calculated by the new method of King, Hainer and Cross instead of Randall, Dennison, Ginsburg and Weber's approximate calculation employed by Elsasser, ii). Van Vleck and Weisskopf's investigation on the line shape, and Becker and Autler's investigation on half-width of a line were referenced, iii) recent investigations of Van Vleck and King, Hainer and Cross were referenced, and several lines expected by their theory were employed in calculationg absorption coefficient. iv). absorption coefficient of ν₂ band between 5μ and 8μ, which Elsasser did not calculated theoretically owing to the lack of available data at that time, was calculated by employing Nielsen's and other data.
The comparison of our results with those of Elsasser shows that in band our values of generalized absorption coeffioient which is introduced by Elsasser are much larger than those of Elsasser. It must be remarked that Elsasser's values for ν₂ band are those assumed from the measurements of Fowle and Hettner, and are not calculated theoretically. Also in the intermediate region between 8μ and 25μ, our values of absorption coefficient are to some degree larger than those of Elsasser. This may probably due to the fact that the line shape assumed by us are different from Elsasser's assumption. In the rotational band beyond 17μ both Elsasser's and our values of generalized absorption coefficient are practically came.