Knowledge Bank

Absolute infrared absorption intensities have been measured for the fundamental CO stretching vibration of CO in the pure solid and for CO in Ar matrices. The band shape of the CO absorption has been carefully studied as a function of concentration in the Ar matrix, leading us to support the interpretation that the structure on this band is due to polymer”, dimer” and monomer” $absorption.^{1}$ The baseline for measuring the absolute intensity of the CO absorption in condensed phases has been chosen to give the same second $moment^{2}$ for the band in all phases, following a suggestion by R. G. $Gordon.^{3}$ This objective choice of baseline reduces the scatter in experimental intensities by about a factor of two. A detailed analysis of the second and fourth moments of the band in pure solid CO and for CO in Ar matrices provides an estimate of the intermolecular torque” acting to resist rotation of CO in these $systems.2$ Dipole time-correlation $functions4$ have been calculated for these systems. All these results are compared with corresponding measurements and calculations (made somewhat less carefully) for CO in $C6H6$, in $CCl4$, and in $SF6$ matrices. The authors are grateful to the National Science Foundation (Grant No. GP-17818) for partial financial support. Present address of George J. Jiang: Department of Chemistry, Bowdoin College, Brunswick, Maine, 04011. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ (a) G. E. Leroi, G. E. Ewing and G. C. Pimentel, J. Chem. Phys., 40, 2298 (1964); (b) J. B. Davies and H. E. Hallam, Trans. Faraday Soc., 68, 509 (1972). $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ R. G. Gordon, J. Chem. Phys., 39, 2788 (1963); ibid., 40, 1973 (1964); ibid., 41, 1819 (1964). $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ R. G. Gordon, private communication. $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}$ (a) R. G. Gordon, J. Chem. Phys., 43, 1307 (1965); (b) H. Shimizu, J. Chem. Phys., 43, 2453 (1965).