Dependence of the effective total cross sections [panels (a) and (b)] and [panels (c) and (d)] for collisions of CH2 in its [panels (b) and (d)] and [panels (a) and (c)] states with helium as a function of the collision energy. Red curves: 000 level; blue curves: 808 level. The black curves were computed with the spherical average (V 00 term in the angular expansion) of the respective PESs. Also included in panels (a) and (b) is the elastic contribution to the effective total cross section for the 00 level, computed with the full PES.
State-dependent collision integrals in units of 10−11 cm3 s−1 as a function of the rotational angular momentum j for –He at a temperature of 300 K. Red and blue symbols denote ortho and para levels, respectively. In panels (a) and (b), levels with different values of the body-frame projection quantum number are denoted by the following symbols: k a = 0, circles; k a = 1, plus signs; k a = 2, diamonds; k a = 3, upward-pointing triangles; k a = 4, downward-pointing triangles; k a = 5, left-pointing triangle; k a = 6, right-pointing triangle; k a = 7, squares.
The collision integrals Ω(1, 1) and Ω(2, 2) as a function of temperature, computed for the –He systems. The full PES and the spherical average of the PES was employed for both electronic states.
Differential cross section for elastic –He collisions at a relative translational energy of 300 cm−1: Blue, full PES for the 00 initial level; red, spherically averaged potential. The inset shows the angle-dependent contribution to the Q (1) effective elastic cross section for the two potentials; the area under a curve multiplied by 2π equals the effective elastic cross section.
Diffusion coefficients for the –He systems, computed with the full PESs and their isotropic, spherical averages.
Diffusion coefficients for the CH2–He system: Black and red lines, quantum scattering calculations using ab initio CH2–He PES for the and states, respectively; blue and green lines, classical scattering calculations using Lennard-Jones 12-6 and 9-6 potentials, respectively.
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