Broadening of CH3F in presence of Stark fields. II. Collisional coupling between the Stark components

The collisional line shape of methyl fluoride rotational transitions J,K=2, 2-->3,2 and 5,5-->6,5 is observed under the effect of a static electric fie ld. The collisional coupling between partially overlapping Stark components is studied under two particularly favorable conditions: first, the degree of overlapping can be set by both the electric field and the pressure, seco nd, we have a calculated collisional relaxation matrix checked on both well isolated and completely unresolved Stark components. This allows us to obt ain better insight into the collisional coupling effect and to show definit ely that this effect explains the difference between collisional linewidths of the CH3F rotational transitions and of their Stark components. (C) 1999 American Institute of Physics. [S0021-9606(99)01119-8].