Aiko Huckauf

The Ar-HCCCN van der Waals complex: Microwave spectroscopy and coupled cluster calculations

Large-scale coupled cluster calculations have yielded an almost T-shaped equilibrium structure for the Ar–HCCCN van der Waals complex, with an equilibrium dissociation energy of De=221 cm−1. The theoretical predictions are confirmed by pulsed-nozzle Fourier transform microwave spectroscopy in the frequency range from 3 to 26 GHz. Strong b-type and much weaker a-type transitions have been observed, and the 14N nuclear quadrupole hyperfine components of the rotational transitions have been resolved. The spectral analysis has produced rotational, centrifugal distortion, and 14N nuclear quadrupole coupling constants. Structural parameters describing a (vibrationally averaged) T-shaped complex geometry have been derived.

NC3NC: a combined millimetre-wave spectroscopic and ab initio investigation

Abstract The millimetre-wave spectrum of 2-isocyano-3-propynenitrile, NC 3 NC, was observed in the vibrational ground state (0000) and in the excited bending states ( v 6 v 7 v 8 v 9 )=(1000), (0100), (0010), and (0001). Pure rotational transitions J +1← J were recorded in the ranges 40–120 and 240–315 GHz. The analysis of the spectra, aided greatly by accompanying ab initio calculations, yielded precisely determined rotational, centrifugal distortion, and l -type doubling constants. They are in excellent agreement with the results of coupled-cluster calculations. Wavenumbers and infrared (IR) intensities of various stretching vibrational transitions were calculated variationally. Good agreement with results from high-resolution IR spectroscopy is observed for the highest fundamentals ν 1 – ν 3 , with deviations amounting to 15.4 cm −1 ( ν 1 ), 1.2 cm −1 ( ν 2 ), and 7.0 cm −1 ( ν 3 ).