The ν12-ν9 band of ethane:: A global frequency analysis of data from the four lowest vibrational states

The nu(12) - nu(9) difference band of ethane in the region around 385 cm(-1) has been recorded with a Bruker IFS-120 HR Fourier transform spectrometer at a resolution of 0.003 cm(-1) to characterize interactions between the torsional stacks of symmetric rocking mode nu(12) with its analog motion the anti-symmetric rocking mode vs. This spectrum is analyzed with data from the nu(3) and nu(9) fundamentals, the nu(9) + nu(4) - nu(4) hot band and torsional transitions from the nu(4), 2 nu(4) - nu 4, and 3 nu(4) bands. The combined data set includes more than 4800 frequencies, and was fitted to within experimental accuracy using a 67-parameter model The first determination of molecular parameters for the nu(12) state from a high resolution Hamiltonian. spectrum has been made. The selection rules for the nu(12) - nu(9) band, the development of the coupling terms between nu(9) and nu(12) states and the possible extension of the model to treat the bands of ethane in the 1300 to 1600 cm(-1) region are discussed. (c) 2008 Elsevier Inc. All rights reserved.