PRODUCTION OF HALOMETHYLENES IN FREE-JET EXPANSIONS FROM A HOT NOZZLE- IDENTIFICATION AND CHARACTERIZATION OF HCBR AND DCBR BY LASER-INDUCED FLUORESCENCE EXCITATION SPECTROSCOPY

The efficient production of chloromethylene and bromomethylene by hot- nozzle pyrolysis and subsequent supersonic free-jet expansion has been demonstrated. In the case of the bromocarbene, the LIF-excitation spe ctral measurements represent the first direct observations of this spe cies. Visible spectra for both HCBr and DCBr have been obtained and ar e in accord with expectations for a species with nonlinear ground-stat e and quasilinear excited-state geometries. For the protonated species the excited-state bending frequency is near 840 cm-1 when v2 = 5 and the C-Br stretching frequency is nu3 almost-equal-to 783 cm-1.