A SINGLE CONSISTENT SET OF 85 CONSTANTS FOR THE GROUND STATE, THE DIADE AND THE PENTADE OF $^{12}CH_{4}$
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Date
1981
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Ohio State University
Abstract
The simultaneous fit of transitions from the $v_{1}, v_{3}, 2v_{2}, v_{2}+v_{4}$ and $2v_{4}$ bands of $^{12}CH_{4}$ is presented. More than 1500 vibro-rotational energy levels involved in one or more observed transitions up to $J^{\prime} = 15$ have been included. The overall standard deviation is 20 mk. The originality of our theoretical approach lies in two main points: 1 - Off-diagonal terms are developed to the same order than diagonal terms (3rd order). 2 - Rather than using effective rotational parameters for each band, we expand the hamiltonian according to both vibrational and rotational powers. As a result, the only parameters to be refined involve small powers of J. This comprehensive study leads to a single consistent set of parameters reproducing the energy levels of the ground state and the first two polyades of $^{12}CH_{4}$ with a good accuracy. The extrapolation of such an approach for investigating higher polyades is discussed. [FIGURE]
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