H⁺-H^- coincidences from the three-body dissociation of excited H_3⁺

Authors

Orhan Yenen, University of Nebraska-LincolnFollow
D. Calabrese, University of Nebraska - Lincoln
L.M. Wiese, University of Nebraska - Lincoln
Duane H. Jaecks, University of Nebraska-LincolnFollow
Gordon A. Gallup, University of Nebraska-LincolnFollow

Date of this Version

2-1-1993

Comments

Published by American Physical Society. Phys. Rev. A 47, 1059 (1993). http://pra.aps.org. Copyright © 1993 American Physical Society. Permission to use.

Abstract

The laboratory energy distribution of protons in coincidence with an H^- ion, resulting from the dissociation of excited H_3⁺, has been measured for H⁺-H^- pairs emitted along the beam for 4.0-keV H_3⁺-He collisions. An approximate energy distribution of H⁺-H^- pairs for the collinear configuration of the dissociation products is obtained by transforming the measured laboratory spectrum to the H_3⁺ center-of-mass (c.m.) frame. Coincidence data suggest that the reaction producing H⁺-H^- pairs where the H⁺ ion has near-zero energies (3⁺ ions using a full configuration-interaction calculation with a basis set of atomic orbitals consisting of 1s, 1s’, 1p’, 2s, and 2p centered on the protons forming an isosceles (C_2vsymmetry) or an equilateral (D_3h symmetry) triangle. The states leading to asymptotic H⁺+H⁺+H^- limits have been identified by calculating 〈1/r₁₂〉^-1, the inverse of the expectation value of the electron-electron repulsion term. The states identified by this procedure have adiabatic Born-Oppenheimer energies of 40–45 eV above the H_3⁺ ground state at the H_3⁺ equilibrium separation. The limits on the total available internal energy to be shared by the three dissociation products that one obtains from the experimentally determined H⁺-H^- coincidence spectrum are consistent with the identified H_3⁺ excited states.