Polarized infrared spectroscopy of photo-oriented 2-fluoroethanol in solid argon: Mechanism of the mode-specific isomerization

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Abstract
Single photon infrared (IR) photoisomerization of 2-fluoroethanol isolated in solid argon creates selectively photooriented reactant and product distributions. The IR dichroism resulting from polarized excitation of each of six different bands in the CH stretching region, the OH stretching band, and the ν(OH)+τ(OH) combination band is reported. Each irradiation imparts a dichroism to the spectrum of both the G′g reactant and the Tt product isomers. Analysis of this dichroism shows that during isomerization the CH2F end of the molecule remains essentially stationary in the solid; the photoisomerization occurs primarily by internal rotation of the CH2O and OH groups. New vibrational mode assignments in the CH stretching region and a confirmation of a C2 pseudosymmetry in the Gg isomer are also derived from this analysis. These results demonstrate the general efficacy of this novel application of polarized IR spectroscopy.