Rotational energy transfer in CH$_4$ collisions with He atoms*

Methane is an active constituent in the Earth's atmosphere, is one of the important greenhouse gases, is an important species in the atmospheres of T dwarfs, and is likely present in the carbon-rich atmospheres of circumstellar shells. Quantitative determinations of state-to-state cross sections and rate coefficients for the CH$_4$-He scattering system are therefore of interest for numerical models of atmospheric and astrophysical environments. In this work, quantum close-coupling and coupled-state approximation scattering calculations for quenching of rotationally excited CH$_4$ due to collisions with He are performed for collision energies between 10$^{-7}$ and 3000 cm$^{-1}$ using the MP4 potential of Calderoni {\it et al.} [J. Chem. Phys. {\bf 121}, 8261 (2004)]. State-to-state cross sections and rate coefficients from selected initial rotational states of CH$_4$ in symmetries $A$, $E$ and $F$ are presented. Comparison of cross section with available theoretical results and experimental data are also presented.