Precise ground state molecular parameters of chloromethane

This paper presents results of new microwave studies of two chloromethane isotopologues 12CH335Cl and 12CH337Cl. The microwave spectra were obtained using the Prague millimeter wave semiconductor spectrometer with an estimated uncertainty of individual well-developed (well-separated, not saturated with low noise) lines about 5 kHz. The spectra were measured at different pressures and a pressure dependence of the molecular parameters was studied. The measurable pressure dependence was found only for the B constant. Moreover, our new data were merged with top quality data previously published and an additional set of the precise ground state molecular parameters B, DJ, DJK, HJJ, HJK,, HKJ, eQq, and CN was derived for both the isotopologues.