Radio frequency-microwave double resonance as a tool in the analysis of microwave spectra

Abstract

The practical application of radio frequency-microwave double resonance as a spectroscopic technique in the analysis of microwave spectra has been investigated. Application of a high-power amplitude-modulated radio-frequency field to a gaseous sample in a waveguide cell provides a means of detecting microwave transitions, analogous to the situation in microwave-microwave double resonance. The sensitivity of the technique compares favorably with that of Stark modulation. Near-symmetric top molecules with allowed K-type doublet transitions are especially amenable to the technique. Accidental near degeneracies of dipole-connected rotational levels in asymmetric top molecules are also useful. A description of a radio frequency-microwave double resonance spectrometer is given together with a discussion of the special problems associated with radio frequency circuits. Applications of the technique are discussed with examples.