THE MILLIMETER - AND SUBMILLIMETER - WAVE SPECTRUM OF METHYL FORMATE $(HCOOCH_{3})$ AND SYMMETRIC MONODEUTERATED METHYL FORMATE $(DCOOCH_{3})$

Abstract

Although deuterated isotopomers of organic molecules have been detected in various interstellar sources, singly deuterated isotopomers have not yet been detected in the interstellar medium due to a lack of laboratory spectroscopic data. To aid in the study of interstellar spectra, the analysis of the rotational-torsional spectrum of deuterated $methy^{l}$ formate has been extended into the millimeter-wave and submillimeter-wave regions of the electromagnetic spectrum. The A (symmetric) and E (asymmetric) torsional substates of the ground $(\nu_{t} = 0)$ torsional state of deuterated methyl formate have been fit to a rms deviation of 85 kHz using a direct digonalization procedure of an extended global internal -axis method (IAM) Hamiltonian. Using this global IAM approach, the A and E states of the ground torsional state for methyl formate have been reanalyzed and a rms deviation of less than 100 kHz has been obtained for the global fit of our data.