PAPE band (ν6+ν8)0 and the hot bands ν6+ν8-ν8 of CD3CN

The infrared spectrum of CD3CN around 1380 cm(-1) has been studied at a resolution of 0.0040 cm(-1). in this region the combination of two perpendicular fundamentals nu(6) and nu(8) is located. In the spectrum only the parallel component was observed although the path length was 150 m and the pressure 70 Pa. In this PAPE type band 1340 lines were assigned in 17 sub-bands. The vibrational e-doubling and -resonance together with strong effects of rotational l-resonances with the perpendicular component of the same vibrational level were observed. In addition, the Coriolis resonance with nu(3) + nu(8) and certain anharmonic perturbations complicated the analysis. To create a better model both the hot bands (nu(6) + nu(8))(0) - nu(8) and (nu(6) + nu(8))(2) - nu(8) were assigned (1508 lines) and analyzed together with the PAPE band. In the hot band (nu(6) + nu(8))(0) - nu(8) the Q branch (P)Q(1) around 1049.5 cm(-1) was found to have a doublet structure and the splitting in the sub-band gave direct information about the vibrational e-doubling. The splitting of K Delta K = 1 sub-band in (nu(6) + nu(8))(2) - nu(8) giving rise to two families of lines was detected, too. In the calculations attention was paid to the main features of the PAPE problem, Higher order fitting parameters were avoided to keep the results reliable. The standard deviation 2.7 x 10(-3) cm(-1) may be considered satisfactory, when taking into account the complexity of the whole system. (C) 2000 Elsevier Science B.V. All rights reserved.