Kinetic and Electronic Energy Dependence of the Reactions of Sc + and Ti + with D 20

The reactions of Sc+ and Ti+ with D20 are studied as a function of translational energy in a guided ion beam tandem mass spectrometer. Both ions react to form three ionic products: MD+, MO', and MOD'. MO+ formation occurs exothermically by dehydrogenation of D20, even though this reaction is spin forbidden for reaction of ground state M+ in both systems. In the titanium system, the effect of electronic energy on product formation is probed by varying the conditions used for forming Ti+. The a2F state of Ti+ reacts much more efficiently than the a4F ground state at forming all three product ions. The relative reaction efficiencies are consistent with a recent study of the reverse reactions of MO+ + D:! [J . Phys. Chem. 1993, 97, 5441. State-specific cross sections and the competition between the various products indicate that the reactions occur primarily through a low-spin state of a D-M+-OD intermediate. Thresholds of the cross sections for endothermic formation of all three product ions are consistent with values calculated by using previously measured bond energies.