Far-Infrared Synchrotron Spectroscopy of a Potentially Important Interstellar Isotopologue of Vinyl Alcohol: CH₂CHOD

The far-infrared spectrum (100-500 cm^-1) of a d₁ isotopologue of the astrophysically important molecule, vinyl alcohol, is reported. We observed several low energy (OD) torsional bands: the fundamental and first two hot bands of the syn rotamer and the fundamental and first hot band of the (higher energy) anti rotamer. While the bands corresponding to the anti rotamer are somewhat obscured by rotational lines of water (making a full spectroscopic analysis unfeasible at this stage), the syn-vinyl alcohol bands are not, and a global fit was performed that included 4404 distinct infrared lines assigned in this work, in addition to 59 previously reported microwave lines. This simultaneous analysis of the torsional fundamental, torsional hot band, and pure rotational band of syn-vinyl alcohol allowed for determination of spectroscopic parameters in the first two torsionally excited states and for refinement of them in the ground state. These parameters should be useful in searches for both cold and warm CH₂CHOD in interstellar molecular clouds.