THE RAMSAUER MINIMUM OF METHANE

Vibrationally elastic, rotationally-summed cross sections for electron collisions with CH4 are calculated with ab initio static + exchange ( SE) interactions and using a symmetry-adapted, single-centre expansion (SCE) representation for the close-coupled (CC) equations. The dynami cal correlation forces are included through a local density-functional theory (DFT) approach. Both integral and differential cross sections are calculated at the Ramsauer-Townsend (RT) minimum and at energies c lose to it. Comparisons with experiments and with previous calculation s show that the present approach exhibits one of the best overall acco rds with measurements while still keeping the computational effort wit hin modest limits.