Quantum reaction dynamics of Cl+HCl→HCl+Cl:: vibrationally non-adiabatic reactions

Quantum reaction dynamics of Cl + HCl --> HCl + Cl for J (total angular momentum)= 0 is studied with use of the hyperspherical elliptic coordinate approach recently proposed by the authors. Thanks to the numerical efficiency of this approach, the reactions involving vibrational quantum jumps up to three are calculated accurately. Actually, all transitions among the states up to nu = 3 and j = 15, in other words up to the total energy E = 1.3 eV, are covered, where nu and j represent vibrational and rotational quantum numbers, respectively. Because of the symmetry of the system, the vibrationally adiabatic reactions are generally more probable than the non-adiabatic ones. However, some specific vibrationally non-adiabatic reactions even with two or three vibrational quantum jumps are found to occur efficiently. The concepts of potential ridge and non-adiabatic transitions at avoided crossings near the ridge lines enable us to comprehend the reaction mechanisms nicely. (C) 1999 Elsevier Science B.V. All rights reserved.