High-resolution infrared and theoretical study of the fundamental bands nu(2), nu(4) and nu(9) and the c-Coriolis interacting dyad nu(5), nu(14) of 1,3,4-thiadiazole

摘要

The Fourier transform gas-phase IR spectrum of 1,3,4-thiadiazole, C2H2N2S, has been recorded with a resolution of ca. 0.003 cm(-1) in the 800-1500cm(-1) spectral region. Five fundamental bands nu(2)(A(1); 1391.9cm(-1)), nu(4)(A(1); 964.4cm(-1)), nu(5)(A(1); 894.6cm(-1)), nu(9)(B-1; 821.5 cm(-1)), and nu(14)(B-2; 898.4 cm(-1)) have been analysed using the Watson model. Ground state rotational and quartic centrifugal distortion constants as well as upper state spectroscopic constants have been obtained from fits. The nu(4) and nu 9 bands are unperturbed while a strong c-Coriolis resonance perturbs the close-lying nu(5) and nu(14) bands. This dyad system has been analysed by a model including first and second order c-Coriolis resonance using the theoretically predicted Coriolis coupling constant zeta(c)(14,5). The nu(2) band is strongly perturbed by a local resonance, and we obtain a set of spectroscopic parameters using a model including second order a-Coriolis resonance with the inactive nu(10) + nu(14) band. Ground state rotational and quartic centrifugal distortion constants, anharmonic frequencies, and vibration-rotational alpha-constants predicted by quantum chemical calculations using a cc-pVTZ basis and B3LYP methodology, have been compared with the present experimental data, where there is generally good agreement. (c) 2008 Elsevier Inc. All rights reserved.