Rotational Spectrum and Structure of the Ar–HCCCN van der Waals Complex.
Aiko Huckauf and Wolfgang Jäger
University of Alberta, Edmonton AB T6G 2G2, Canada
We report the results of the first rotational spectroscopic investigation of the Ar–HCCCN van der Waals complex.
HCCCN was prepared from commercially available ethyl propiolate according to literature methods [1]. For our investigation, we used a dilution of 0.2% ethynyl cyanide in argon at a total pressure of 3 to 4 atm.
The spectrum was recorded in the frequency region from 4 to 26 GHz using a molecular beam Fourier transform microwave spectrometer with a resolution high enough to resolve the 14N nuclear quadrupole hyperfine components of the rotational transitions. Strong b- and much weaker a-type lines were observed, and the spectrum is consistent with a vibrationally averaged T-shaped complex geometry. The analysis yielded rotational, centrifugal distortion, and 14N nuclear quadrupole coupling constants which were used to derive structural parameters and information about the large amplitude intermolecular motion.
[1] C. Moureau and J. C. Bongrand, Bull. Chem. Soc. 5, 846 (1909).