Time-dependent quantum wave packet studies of the F + HCl and F + DCl reactions

Full three-dimensional time-dependent quantum wave-pack calculations have b een carried out for the F+HCl and F+DCl reactions on a many-body expansion of the ground 2A(')HClF potential energy surface. The calculated energy-dep endence of reaction probability exhibits oscillating structure in the F+HCl reaction but not in the F+DCl system. The effects of initial state excitat ion on the total reaction probabilities as a function of collision energy a re investigated for reactions from various initial vibrational and rotation al states of HCl and DCl. Our results show that reagent vibrational and/or rotational excitation can generally lead to an increase in reaction probabi lity at low collision energy and a slight decrease at relatively high colli sion energy. Thermal rate constants for the title reactions are calculated and they are in generally good agreement with experimental measurement. Inv estigation of steric effects for the reactions indicates that the H (or D) side of HCl (or DCl) molecule is only slightly favored for reactive attack and reaction proceeds from almost all attack angles. The present results in dicate that the H/D kinetic isotope effect should not be totally neglected. (C) 2000 American Institute of Physics. [S0021- 9606(00)01746-3].