The Cs(7p)+H2→CsH+H reaction. III. Quasiclassical trajectory study.

A quasiclassical trajectory study of the Cs(7p)+H2→CsH+H harpooning reaction at thermal energies is carried out on a single potential energy surface. Extensive calculations are performed in a 2D space since 3D calculations show that all trajectories are nearly confined into the collision plane. Calculated rotational and angular distributions of CsH products are in good agreement with experimental data. The best agreement is obtained using a potential energy surface with no potential barrier in the exit valley. Some dynamical features are demonstrated through an analysis of correlations between various collision parameters. Migrations of the electronic charge ‘‘-’’ from one H atom to the other during the collision induce important dynamical effects; in particular, they increase the collision time and reduce CsH product vibrational energy. The duration of the collision, the deflection angle, the angle between J’ and L’ (internal and orbital output angular momenta) and the translational energy of products are closely related to the impact parameter; there is a radical change in the behavior of the system according to the impact parameter being smaller or greater than the critical value bc[bar_over_tilde:_approx._equal_to]2.8 Å. For b≤bc, the collision time is constant, the deflection function is linear, J’ and L’ are either parallel or antiparallel; for b≥bc, the collision time increases with b, an isotropic component appears in the deflection function, and J’ and L’ are always parallel. The geometry of approach has no influence on the dynamics of the collision. Angular and rotational distributions are not modified when taking into account the nonreactive channels correlated to Cs(6s,6p,5d,7s)+H2. [ABSTRACT FROM AUTHOR]