THE DIFFERENCE BANDS OF TETRAHEDRAL MOLECULES - APPLICATION - THE 2V4-V4 AND V2+V4-V2 HOT BANDS OF CH4-C-12

This article presents a general method, based on the tensorial formalism in the T//d group, for the computation of difference bands of tetrahedral XY//4 molecules. This work is applied to the 2 v//4 minus v//4 and v//2 plus v//4 minus v//2 bands of **1**2CH//4. In the case of 2 v//4 minus v//4 we treated also the problem using the spherical formalism which yields more directly the selection rules. 295 transitions of the IR spectrum of methane recorded at O. N. E. R. A. in the region from 1216 to 1355 cm** minus **1 have been assigned to the 2 v//4 minus v//4 and v//2 plus v//4 minus v//2 bands. Among them 79 are concerned with the v//4 equals 2,1//4 equals 0 (A1) sub-level. 49 of them (J less than equivalent to 7) have been used in a new determination of the parameters of this sub-level.