Argon-broadened line parameters in the nu(3) band of (CH4)-C-12

Prompted by improved measurements of collisional line shapes in the v(3) band P, Q and R branches of (CH4)-C-12, we have performed semi-classical line broadening calculations for methane perturbed by argon. We have used the theoretical approach developed by Robert and Bonamy as an extension of the well-known Anderson-Tsao-Curnutte theory. The semi-classical theory as reformulated here is shown to fully account for the tetrahedral symmetry of methane type molecules. The variation of argon-broadened linewidth coefficients in the vl band of (CH4)-C-12 with the branch, J, symmetry and energy level fine structure is discussed. (C) 1997 Elsevier Science Ltd.