The high-resolution FTIR spectrum of the ν4 + ν8 band of trans-d2-ethylene (trans-C2H2D2)

The FTIR absorption spectrum of the hybrid A-B type nu(4) + nu(8) combination band of trans-C2H2D2 centered at 1845.98737 cm(-1) in the 1730-1940 cm(-1) region was recorded at an unapodized resolution of 0.0063 cm(-1). A total of 2725 a- and b-type transitions was assigned and fitted to upper state (nu(4) + nu(8) = 1) rovibrational constants up to sextic terms using Watson's A-reduced Hamiltonian in I-r representation. The b-type feature of the band was analyzed for the first time. The root-mean-square deviation of the IR fit was 0.00059 cm(-1). The most accurate set of ground state rovibrational constants up to sextic terms was also derived from the simultaneous fit of 3340 ground state combination differences from the present analysis and the nu(4) band of trans-C2H2D2. The transition dipole moment ratio vertical bar mu(a)/mu(b)vertical bar was found to be 1.95 +/- 0.06. (C) 2011 Elsevier Inc. All rights reserved.