The FT microwave spectrum of benzo[ b ]thiophene: first application of a new heatable beam nozzle

A new beam nozzle for a cavity FT microwave spectrometer has been developed that can be heated, even in close contact with massive aluminum mirrors, to temperatures up to 473 K (200°C). It has been used to evaporate a sufficient amount of benzo[b]thiophene to record and assign its rotational spectrum in the vibronic ground state of the normal and the 34S isotopomer. Spectra of some excited vibrational states of the normal isotopic species were also found and assigned. In both cases rotational and quartic centrifugal distortion constants are reported.