Vibration-Rotation Interaction Constants, l-Type Doubling Constants and Cubic Force Constants of CH3I and CD3I

Abstract
The harmonic parts of the vibration-rotation interaction constants and the l-type doubling constants were calculated for CH3I and CD3I from the harmonic force field. The harmonic parts were subtracted from the experimental values to obtain the anharmonic parts which give relations among the cubic normal-coordinate force constants. Some of the individual values for the cubic force constants associated with the bending modes were obtained by using the derived relations and the previously estimated values for the stretch-stretch-stretch cubic force constants of the methyl group.