High resolution spectrum of the v=1 Π state of ArHCN

Submillimeter Detection of the van der Waals Stretching Vibration of the Ar-CO Complex

With the Cologne submillimeter-wave supersonic jet spectrometer, we extended molecular jet spectroscopy with backward wave oscillators up to frequencies of about 600 GHz. For the first time, the van der Waals stretching vibration of the Ar-CO molecular complex was detected in direct absorption. We measured 13 ro-vibrational transitions (Kvstretch = 1 <-- 0, Ka = 0 <-- 0) in the frequency range from 528 to 600 GHz and additionally the two R(3) K doublet (Ka = 4 <-- 3) pure rotational transitions at 447 GHz with an accuracy of about 200 kHz. The ro-vibrational transitions were assigned and fitted within experimental accuracy to a simple Hamiltonian taking into account the Coriolis interaction between the stretching and bending states, i.e., between vstretch = 1, Ka = 0, and vbend = 1, Ka = 1. The intensity of the transitions in the van der Waals stretching mode was estimated to be a factor of 5-10 less than that in the bending mode of Ar-CO. Copyright 1999 Academic Press.

Submillimeter-Wave Absorption Spectroscopy of the Ar-CO Complex: Detection of the van der Waals Bending Vibration

Van der Waals bending rovibrational transitions of the Ar-CO complex were observed between 308 and 383 GHz using submillimeter-wave absorption spectroscopy in a pulsed supersonic jet. The submillimeter radiation was generated by a phase-stabilized backward wave oscillator source. Fourteen transitions of the P and R branch of the bending vibration were measured with an accuracy of about 100 kHz. The frequencies were fitted using effective molecular parameters including the band origin and the rotational constants for the ground state and for the excited bending vibrational state.