Some Infrared Spectra of Matrix-Isolated Lithium Fluoride

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Abstract
Infrared spectra of LiF species suspended in solid Ne, O2, CO, and CH4 at liquid‐helium temperature have been obtained. The monomeric LiF frequency (in cm−1) is 869 in Ne, a doublet at 819–824 in O2, 787 in CH4, and a doublet at 710–725 in CO, compared to 895 cm−1 in the gas phase. Some of these values seem consistent with Linevsky's statement that the solvent shift in LiF is primarily of electrostatic origin. Electrostatic calculations were made for the rare‐gas matrices in order to observe the effects of asymmetric solute positions in the ideal lattice substitutional site and to test ideal lattice breakdown, or ``solvation'' of the monomeric LiF solute. For reasonable distance parameters, both types of calculation can account for most, or all, of the observed solvent shift. These simple calculations show ways to reduce the dispersive contributions to commonly observed values but likewise illustrate the presently unsatisfactory state of a genuine understanding of the LiF—matrix systems.