A Study of the Pressure Broadening of Three Pure-Rotation Lines of Hcl

摘要

Communication systems of the future will use the far-infrared region of the electromagnetic spectrum extensively. Before use of the submillimeter region of the spectrum becomes practical, components such as filters must be developed and synthesized. The study experimentally establishes the feasibility of using HCl as a variable bandwidth, band-elimination comb filter at specific far-infrared frequencies. The pressure broadening of the J(1), J(2), and J(3) transitions of HCl has been studied using a far-infrared interferometer. Line parameters obtained with the method of equivalent widths are compared with parameters calculated on the basis of Lindholm's pressure-broadening theory. Disagreement with theory and earlier experimental studies are discussed. The observed half-widths of all three transitions are much smaller than predicted by Lindholm, but qualitative agreement with theory is obtained. Thus, the use of a molecular gas, HCl, is shown to be a practical means of constructing far-infrared filters. (Author)