The first high-resolution analysis of the low-lying ν9 band of propane

Abstract

The ν 9 fundamental band (C–C–C deformation) of propane (C 3H 8) at 369 cm −1 has been studied at high-resolution (0.0011 cm −1) with spectra recorded using the synchrotron radiation from the French light source facility at SOLEIL coupled to a Bruker IFS 125HR Fourier transform spectrometer. A 2.526 m base multipass cell with optical paths from 10.296 to 151.78 m was used. In addition, a spectrum was also recorded using a conventional globar source. Comparison of these experimental spectra shows clearly the gain obtained on the signal-to-noise ratios with the synchrotron radiation. The spectra have been thoroughly analyzed and transitions up to J=65 and K a=33 have been assigned. The upper-state rotational levels were fitted using an A-type Watson Hamiltonian written in the I r representation. An accurate band center ν 0 ( ν 9)=369.228080(25) cm −1 as well as accurate rotational and centrifugal distortion constants have been obtained and used to simulate a synthetic spectrum. These parameters should be useful to simulate hot bands of propane involving the 9 1 vibrational level as their lower state.