Torsional Splittings and Assignments of the Doppler-Limited Spectrum of Ethane in the C-H Stretching Region

Abstract

The Doppler-limited absorption spectrum of the C-H stretching region of ethane has been recorded at T 119 K with a tunable difference-frequency laser spectrometer. The strong torsional hot band structure at room temperature is eliminated at 119 K, and the enhanced resolution from the Doppler width reduction allows us to observe small torsional splittings. The two fundamentals in the region, v., a perpendicular band and, v , a parallel band have been essentially completely assigned as have a large number of transitions in the parallel component of the v8 + V11 combination band. A number of perturbations of both global and local nature have been observed. The complete spectrum and a listing of transition wavenumbers, intensities and assignments are presented here to facilitate identification and quantitative analysis of ethane in a variety of monitoring applications. Precise ground state rotational constants have been determined from combination differences.

A NEWLY DEVELOPED FLUORESCENCE MODEL FOR C2H6ν5AND APPLICATION TO COMETARY SPECTRA ACQUIRED WITH NIRSPEC AT KECK II

“…The ground state rotational constants (cm −1 ) are provided in Pine & Lafferty (1982) The energy (cm −1 ) of each rotational level is given by Herzberg 1945), where J is the rotational quantum number, and K is the quantum number that corresponds to the component of the total angular momentum vector along the figure axis (K J, since K is the projection of J). We obtained statistical weights for the rotational levels from Dang-Nhu et al (1984;also Wilson 1938).…”

“…Upper state rotational constants for ν 5 are not presented in the literature; so we obtained them by fitting experimental data given by Pine & Lafferty (1982), for each K ladder (since each ladder is subject to perturbations; see Table 1). Pine & Lafferty recorded the absorption spectrum of ethane with a tunable differencefrequency laser spectrometer, and they provide a frequency and intensity for each measured line and identifications of J , K , J , and K for many lines.…”

Working Group 5: Molecular Spectroscopy

“…Gas phase infrared spectra are reported for A1F and KF (92), benzene (93), ethane (94,95), SnO(96), OCS far infrared(97), CO(98) LiF (99) and C02 (100).…”

Infrared excitation processes of C2H6 in comets

“…Cole et al (1980) listed some line positions of the band, but they did not present line strengths, and ground state energies. Pine and Lafferty (1982) recorded the band with a spectral resolution of 0.0043 cm −1 in the 2870-3050 cm −1 range and listed rotational quantum numbers, ground state energies, and experimentally obtained line intensities, along with line positions. However, the line list does not have line positions of sub-branches, such as R Q 0 , R Q 1 , etc., because the accumulated lines of the subbranches could not be resolved in their data.…”