The [formula omitted] band of ethane: A global frequency analysis of data from the four lowest vibrational states

Abstract

The ν 12 - ν 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 ν 12 with its analog motion the anti-symmetric rocking mode ν 9 . This spectrum is analyzed with data from the ν 3 and ν 9 fundamentals, the ν 9 + ν 4 - ν 4 hot band and torsional transitions from the ν 4 , 2 ν 4 - ν 4 , and 3 ν 4 bands. The combined data set includes more than 4800 frequencies, and was fitted to within experimental accuracy using a 67-parameter model Hamiltonian. The first determination of molecular parameters for the ν 12 state from a high resolution spectrum has been made. The selection rules for the ν 12 - ν 9 band, the development of the coupling terms between ν 9 and ν 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.