INFRARED SPECTROSCOPY AND PHOTOCHEMISTRY OF NITROMETHANE ADSORBED ON ALKALI HALIDE FILMS: CONFORMERS AND QUENCHING

Author Institution: Department of Chemistry, University of ScrantonNitromethane was adsorbed at low temperature onto sublimited alkali halide films. We have observed two conformational isomers on these surfaces, manifest as a temperature-dependent splitting of the asymmetric C-H stretching modes. The energy difference and barrier height to interconversion between these conformations were determined for molecules adsorbed on NaCl, NabR, KCL, and KBr films over temperatures ranging from 12K to 160 K. Irradiation of the adsorbate at wavelengths above 250 nm does not yield any observable photoproducts, while irradiation using wavelengths below 250 nm produces a variety of photoproduct species. The surface apparently has little effect on the $\pi-\pi^{*}$ (198nm gas phase) photochemistry, but quenches the $n -\pi^{*}$ photochemistry (singlet-singlet: 270 nm; singlet-triplet: 326nm) to an undetectable level