Line strengths, line widths, and dipole moment function for HCl
Abstract
Previous expressions for the dipole moment matrix elements of the vibrationrotation bands of diatomic molecules, based on a quintic anharmonic oscillator potential, a cubic dipole moment function, and third order perturbation theory, are extended for the 10 and 20 bands to include secondorder contributions. Line intensities in the 10 band of HCl are measured with 0.02 cm ^{1} resolution and analyzed to obtain a band intensity S _{0}^{1} of 135 cm ^{2} atm ^{1} at 300°K and the following HermanWallis factor: F _{0}^{1}(m) = 1  0.0260 m + 4.5 × 10 ^{4}m ^{2}. Similar measurements are made in the 20 band of HCl with 0.04 cm ^{1} resolution and yield S _{0}^{2} = 3.73 cm ^{2} atm ^{1} and F _{0}^{2}(m) = 1  0.0086 m + 4.1 × 10 ^{4}m ^{2}. These results and the previous 30 band intensity data are incorporated with the dipole moment matrix elements above to obtain the following dipole moment function for HCl: M( r) = 1.095 + 0.905( r  r_{e})  0.066( r  r_{e}) ^{2}  0.73( r  r_{e}) ^{3}, where r  r_{e} is in angstroms and M( r) is in Debyes. The halfwidths of selfbroadened lines of HCl in the 20 band are measured directly. The results are somewhat lower than previous measurements for  m < 8. Previous results for the dipole moment function of HCl are discussed as is the importance of secondorder contributions to the dipole moment matrix elements. It is pointed out that the Morse oscillator results for HCl for a quadratic dipole moment agree reasonably well with those of the anharmonic oscillator.
 Publication:

Journal of Molecular Spectroscopy
 Pub Date:
 July 1970
 DOI:
 10.1016/00222852(70)901694
 Bibcode:
 1970JMoSp..35..110T