Dissociative Charge Exchange of HeH+: An Experimental Study of the HeH Molecule

We have studied the dissociation of HeH molecules produced in the charge exchange between fast He${\mathrm{H}}^{+}$ ions and Cs. The released kinetic energy is measured by detection in a delayed coincidence technique of the neutral He-H pairs formed after dissociation. First direct evidence is reported for quasibound, predissociative states of HeH with energy levels in agreement with theoretical predictions. HeH* molecules are formed with large rotational and little vibrational excitation. The decay mechanisms of the low electronic excited states of HeH are discussed.