The Ramsauer minimum of methane

Vibrationally elastic, rotationally-summed cross sections for electron collisions with CH 4 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 dynamical 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 close to it. Comparisons with experiments and with previous calculations show that the present approach exhibits one of the best overall accords with measurements while still keeping the computational effort within modest limits.