The ground state of methane 12CH4 through the forbidden lines of the ν3 band |
| |
Authors: | G Tarrago M Dang-Nhu G Poussigue G Guelachvili C Amiot |
| |
Institution: | Laboratoire de Spectroscopie Moléculaire I, Université de Paris VI, tour 13, Place Jussieu 75230 Paris, France;Laboratoire Aimé Cotton, C.N.R.S. II, Bat 505,91405 Orsay, France |
| |
Abstract: | High resolution spectra of the ν3 band of methane, 12CH4, were recorded by using a “third generation vacuum Fourier interferometer”; a large pressure range (from 0.009 to 10 Torr) with a sample path fixed at eight meters was used, enabling observation of transitions with intensity ratios as low as . More than 350 forbidden transitions of the ν3 band, including about 125 transitions of the Q+ branch, were unambiguously identified. Of the 277 transitions retained for computations, one-hundred have 11 ≤ J ≤ 16. From combination difference relations using pairs of transitions having the same upper state energy level (forbidden-allowed and forbidden-forbidden pairs were used), 276 independent differences between ground state energy levels could be determined with uncertainties of about 0.001 cm?1.These data yielded the following values for the ground state structure constants of 12CH4 along with their standard deviations (in cm?1): , , , , , , Thus, for the first time, the scalar constant π0 has been evaluated and ir values have been obtained for the two tetrahedral constants ?0 and ξ0; furthermore, these values are in very good agreement with the ones recently determined from radiofrequency data, i.e., in cm?1: , , From these values, the 276 differences can be reproduced with an overall rms deviation equal to 0.0009 cm?1.Finally, the ground state energies of 12CH4 have been calculated for J ≤ 16. |
| |
Keywords: | |
本文献已被 ScienceDirect 等数据库收录! |
|