High resolution investigation of the 7 mm region of the ethane spectrum

Building upon previous studies, we re-investigated the ethane spectrum between 1330 and 1610 cm -1 by combining unapodized spectra obtained at room temperature with a Bruker Fourier transform spectrometer (FTS) in Brussels and at 131 K with a Bruker FTS in Pasadena. The maximum optical path differences (MOPD) of the two datasets were 450 and 323.7 cm, corresponding to spectral resolutions of 0.0020 and 0.0028 cm -1, respectively. Of the 15,000 lines observed, over 4592 transitions were assigned to the n6 (at 1379 cm -1), n8 (at 1472 cm -1), n4 + n12 (at 1481 cm -1) and 2n4 + n9 (at 1388 cm -1) bands, and another 1044 transitions were located for the n4 + n8 À n4 hot band (at 1472 cm -1). Our new analysis included an improved implementation of the Hamiltonian calculation needed to interpret the complex spectral structures caused by numerous interactions affecting these four modes of vibration. From these results, we created the first line-by-line database containing the molecular parameters for over 20,000 12C2H6 transitions at 7 mm.