TRANSLATIONAL ENERGY EFFECTS IN THE EXCITED CA(D-1(2))-]CACL(A)+H REACTION - EXPERIMENTS AND A HARPOONING MECHANISM(HCL)

By using the time-of-flight technique under crossed-beam conditions, t he collision energy dependence of the Ca(D-1) + HCl --> CaCl(A) + H re action cross-section has been measured over the 0.2-0.5 eV collision e nergy range and found to have a broad peak at 0.3 eV. An empirical des cription of entrance covalent channels-including orbital alignment eff ects due to the open-shell nature of calcium atoms-and a harpooning me chanism, involving ionic charge-transfer states, account for the obser ved translational energy dependence of the reaction cross section.