High-resolution infrared and microwave study of the ν20 and ν21 levels near 300cm-1 in 1,2,4-triazine

The gas phase far-IR spectrum of the v(20) (A", 367.88 cm(-1)) and v(21) (A", 311.28 cm(-1)) bands of 1,2,4-triazine, a five membered ring having the point group C,, has been studied at a resolution ranging from 0.002 to 0.003 cm-1. From the MW spectrum 58 transitions in the v(20) level and 64 in the v(21) level have been assigned. The v(20) and v(21) modes which are due to non-planar motions of the ring system are found to be nearly unperturbed. From a simultaneous analysis of IR and MW transitions band centers, rotational constants, and the quartic centrifugal distortion constants Deltaj, Delta(JK), Delta(K), delta(J), and delta(K) have been obtained using the Watson Hamiltonian, A-reduction, IIIr-representation. (C) 2002 Elsevier Science (USA). All rights reserved.