WIDTHS OF HCl OVERTONE LINES AT VARIOUS TEMPERATURES

In an effort to elucidate the roles of the various factors contributing to the self-broadening of molecular lines, width measurements have been made on the overtone band of HCl at several temperatures from 200° K (dry ice) up to 1283° K. The first 10 lines of the R-branch were chosen for study and the recorded data were subjected to treatment by the equivalent width method and by direct analysis of the transmission curve widths, peaks, and slopes.The general pressure broadening theory of Anderson as amplified by Tsao and Curnutte is readily adaptable to the conditions of the present investigation. Calculations based thereon and incorporating the resonant dipole interaction in combination with a non-resonant term which maintains a ("billiard ball") lower limit to the collision cross section at an intermolecular distance, r0, yield widths which generally agree well with the experimental data. The values of the billiard ball cross section ultimately chosen to give an adequate fit were r0 = 6.2, 6.0, 5.7, and 5.5 A corresponding to the temperatures 200, 300, 513, and 1283° K.