Yr. Ou et al., Quasiclassical trajectory study of Mg(3s3p(1)P(1)) plus H-2 reaction on fitted ab initio surfaces, J PHYS CH A, 103(40), 1999, pp. 7938-7948
Quasi-classical trajectory calculations for the reaction of Mg(3s3p(1)P(1))
with H-2 are performed on two potential energy surfaces (PES), the excited
state (1)A' (or B-1(2) in the C-2v symmetry) in the entrance channel and t
he ground state (1)A' (or (1)A(1)) in the exit channel. A many-body expansi
on procedure is adopted for the construction of the analytical fit function
s from the ab initio results. The title reaction involves a nonadiabatic tr
ansition between the two potential surfaces. For simplicity, the transition
probability is assumed to be unity when the trajectory goes through the re
gion of surface crossing and changes to the lower surface. The calculated t
otal collisional deactivation and reaction cross sections decrease with the
increase of translational collision energy. The calculated rotational prod
uct distributions are characterized by a bimodal feature both fur the MgH v
= 0 and 1 states. The trend of bimodality is consistent with the observati
on reported in experimental studies. Our inspection of individual trajector
ies reveals that the low-rotational and high-rotational populations are cau
sed by two distinct reaction pathways. This observation supports our previo
us expectation for the microscopic branching via the PES anisotropy. The an
gular product distribution indicates that the reaction proceeds predominant
ly via a linear collision complex. An increase of the collision energy from
2.026 to 8.104 kcal/mol has resulted in a shift of the distribution toward
forward direction. The vibrational product distribution tends to decrease
with the quantum numbers. The ratio of MgH(v = 1) to MgH(v = 0) yields a va
lue of similar to 0.3, which is nevertheless underestimated as compared wit
h the observation of 0.7 +/- 0.2. The reasons for the discrepancy are also
discussed.