THE HIGH-RESOLUTION INFRARED-SPECTRUM OF THE NU(4), NU(5), AND NU(6) BANDS OF TRANS-DI-IMIDE REVISITED

The gas-phase IR spectra of the fundamental band nu5 around 3100 cm-1 and the a,b-Coriolis interacting band system nu4, nu6 around 1300 cm-1 of N2H2 have been recorded with a resolution of ca. 0.008 and 0.005 c m-1, respectively. In nu5 and nu6 an a as well as a b component are ob served. In nu4 a c component and a parallel component which obtains it s intensity from the strong a-Coriolis resonance with nu6 are observed . Both in nu4 and in nu6 we have also identified additional transition s with DELTAK(a) = +/-2, which are due to strong b-Coriolis interactio n. From a simultaneous analysis of ground state combination difference s from the three bands the following ground state rotational constants have been derived: A0 = 10.001203(5) cm-1, B0 = 1.3043373 (6) cm-1, a nd C0 = 1.1499757(6) cm-1. The nu4, nu6 band system has been analyzed by a dyad model which takes into account the a-and b-Coriolis resonanc es between the levels. For the analysis of the nu5 band a weak a-Corio lis interaction with the combination band nu2 + nu4 is included. Upper state spectroscopic constants for the nu4, nu5, and nu6 levels and a number of interaction constants have been determined from these analys es. (C) 1994 Academic Press, Inc.