A quantum-rovibrational-state-selected study of the proton-transfer reaction H2+(X2 Σg+: v+=1-3; N+=0-3) + Ne → NeH+ + H using the pulsed field ionization-photoion method: observation of the rotational effect near the reaction threshold

Using the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully prepared H-2(+) (X-2 Sigma(+)(g): v(+) = 1-3; N+ = 0-5) ions in the form of an ion beam in single quantum-rovibrational-states with high purity, high intensity, and narrow laboratory kinetic energy spread (DElab Delta E-lab approximate to 0.05 eV). This VUV-PFI-PI ion source, when coupled with the double-quadrupole double-octupole ion-molecule reaction apparatus, has made possible a systematic examination of the vibrational-as well as rotational-state effects on the proton transfer reaction of H-2(+) (X-2 Sigma(+)(g) : v(+) ; N+) + Ne. Here, we present the integral cross sections [sigma(v(+); N+)'s] for the H-2(+) (v(+) = 1-3; N+ = 0-3) + Ne -> NeH+ + H reaction observed in the center-of-mass kinetic energy (E-cm) range of 0.05-2.00 eV. The sigma(v(+) = 1, N+ = 1) exhibits a distinct E-cm onset, which is found to agree with the endothermicity of 0.27 eV for the proton transfer process after taking into account of experimental uncertainties. Strong v(+) -vibrational enhancements are observed for sigma(v(+) = 1-3, N+) in the E-cm range of 0.05-2.00 eV. While rotational excitations appear to have little effect on sigma(v(+) = 3, N+), a careful search leads to the observation of moderate N+ -rotational enhancements at v(+) = 2: sigma(v(+) = 2; N+ = 0) < sigma(v(+) = 2; N+ = 1) < sigma(v(+) = 2; N+ = 2) < sigma(v(+) = 2; N+ = 3), where the formation of NeH+ is near thermal-neutral. The sigma(v(+) = 1-3, N+ = 0-3) values obtained here are compared with previous experimental results and the most recent state-of-the-art quantum dynamics predictions. We hope that these new experimental results would further motivate more rigorous theoretical calculations on the dynamics of this prototypical ion-molecule reaction.