Observations of infrared absorbance by the B(2u) and B(3u) fundamentals of rhombic Li(2)F(2) matrix isolated in Xe and Ar.
Infrared absorption spectra of the Li(2)F(2) rhombic dimer isolated in Xe, Ar, and Ar-mixed matrices suggest that rotational stereodynamics occurs for Li(2)F(2) in its Xe trapping site. Providing evidence for this, the absorbance peak for the B(3u) fundamental at 617 cm(-1) changes little upon annealing and heating processes, which cause the B(2u) peak at 534 cm(-1) to lose most of its absorbance strength-despite their common provenience. The explanation is rooted in (a) the volume compatibility of Li(2)F(2) and the Xe vacancy, (b) the D(2h) symmetry of Li(2)F(2), (c) the state-specific generation of rotational stereodynamics by vibrational relaxation of the 534 cm(-1) B(2u) mode, and (d) the IR transparency manifested by Li(2)F(2) isolated in Xe crystallites providing rough alignments between the B(2u) transition dipole and the spectrometer IR beam. Analogous behavior appears to occur for the Xe-isolated LiF monomer.
Redington
Richard L
RL
Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409, USA.