Infrared Matrix Spectra of Lithium Fluoride

Evidence for a linear dimer Li₂F₂ has been obtained by extending the spectral measurements for matrix isolated lithium fluoride into the far infrared region. The vapors from solid ⁶LiF, ⁷LiF, and ⁶LiF/⁷LiF mixtures were deposited in argon matrices at liquid hydrogen temperatures. Vibrational assignments were made on the basis of the following linear species: ⁶Li₂F₂,⁷Li₂F₂, ^{6, 7}Li₂F₂ and ^{7, 6}Li₂F₂. Although the specific geometry of the dimer could not be determined, a normal coordinate analysis supported the spectral interpretation of a linear structure (C _∞ ).