Browsing by Author "S. Singhj"

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Far-infrared absorption in gaseous CH4 and CF4 a theoretical study
(1985) C.G. Joslin; C.G. Gray; S. Singhj
We present a simple theory of the gas-phase far-infrared collision-induced absorption spectra of two molecules with tetrahedral symmetry, methane (CH4) and tetrafluoromethane (CF4). We assume that in these molecules CIA arises through octopolar and hexadecapolar induction. By neglecting the small anisotropics in the intermolecular CH4-CH4 and CF4-CF4 potentials, we can express the spectral profiles as convolutions of single-molecule free rotation spectra with intermolecular translational components. Information theory is used to estimate the ‘least biased’ form for the latter, based on our knowledge of their spectral moments (the calculation of the zeroth through sixth moments is described in an appendix). In this way we avoid the need to make questionable assumptions about the system dynamics. The computed lineshapes are in excellent agreement with the available experimental data. © 1985 Taylor and Francis Group, LLC.