Articles you may be interested inEffect of state-selective reactive decay on the evolution of quantum systemsThe endoergic reaction He + Ht --+ HeH + + H is investigated in a molecular-beam experiment as a function ofH 2 + vibrational energy at c.m. collision energies between 0.3 and 1.9 eV. Reactant ions generated by resonantly enhanced four-photon ionization are impulsively accelerated to collide with a beam of He. Time-of-flight velocity distributions of HeH + , measured at one laboratory angle, yield the differential cross section at c.m. angles () = a· and 180·. A shift from "He rebound" to "H + stripping" behavior accompanies the enhancement in the cross section as the H 2 + vibrational energy increases, which matches previous studies at higher collision energy. Small-impact-parameter events produce HeH + with less recoil velocity (more internal energy) than those at large impact parameters. Within the limits of sensitivity and resolution U~E::::: 0.15 e V), definitive resonance features in the collision energy dependence of du/d(J) are not evident. Improvements in the technique to enable such observations are suggested.