ABSOLUTE INFRARED INTENSITIES IN CRYSTALLINE HCI AND HBr$^{\ast}$

$^{\ast}$ This work was supported in part by the U. S. Army Research Office (Durham). $^{1}$ Hollenberg J. L. and Dows D. A. J. Chem. Phys., 34, 1061 (1961). $^{2}$ Hornig D. F. and Hiebert. G. L. J. Chem. Phys., 27, 752 (1957). $^{3}$ Person W. B. Erickson R. E. \& Buckles R. E. J. Am. Chem Soc., 82, 29 (1960).Author Institution: Department of Chemistry, University of IowaUsing the technique of Hollenberg and $Dows^{1}$ we have measured the absolute intensities of the fundamental X-11 stretching vibration in polycrystalline sample of HCI and HBr. The measured values are approximately $16 \times 10^{43}$ darks for HCI, and $15 \times 10^{43}$ darks for HBr, or an increase of about 12,000 darks over the values measured for the isolated molecules in the gas phase. Surprisingly enough, these intensities are approximately equal to those predicted by Hornig and $Hiebert^{2}$ from consideration of the coupling force constant between adjacent HCl molecules in the crystal and the dipole-dipole coupling model. Alternatively, the observed intensification is approximately equal to that predicted from the observed frequency shift and the relationship given by Person. Erickson and $Buckles^{3}$