DETECTION OF VAN DER WAALS VIBRATIONAL TRANSITIONS USING A NEW MW-THz DOUBLE RESONANCE TECHNIQUE

A new double resonance technique has been developed that can be used for the detection of low frequency van der Waals vibrations. The technique uses backward wave oscillators (OB-24, OB-30, ISTOK), which are phase-locked to a KVARZ mm-wave synthesizer (78-118 GHz), as pump $sources,^{b}$ and a pulsed jet cavity Fourier transform microwave spectrometer for detection. Initial measurements were done on the Ar-CO $system^{c}$ for which the THz frequencies of ro-vibrational transitions from the ground to the first excited van der Waals bending state were known from previous $measurements.^{d}$ Resolving power and sensitivity of the technique will be discussed.