Microwave spectra and electric dipole moments for low-J levels of interstellar radicals: SO, C2S, C3S, c-HC3, CH2CC, and c-C3H2

Abstract

A number of low-J rotational transitions have been measured for the radical or transient molecular species, SO, C2S, C3S, c-HC3, CH2CC, and c-C3H2. Measurements were made with a pulsed nozzle, Fabry-Perot cavity, Fourier transform microwave spectrometer equipped with a dc voltage, electric discharge nozzle. Helmholtz coils around the outside of the vacuum chamber were used to maintain the magnetic field within the active volume element of the Fabry-Perot cavity to less than 10 mG. The transition frequencies measured are accurate in most instances to 4 kHz, thus allowing the molecular dynamics of cold interstellar cloud to be determined with improved accuracy. In addition, the molecular electric dipole moments have been determined for SO, C3S, c-HC3, and c-C3H2 from Stark effect measurements.