Breakup ofH2+by photon impact

Abstract

Total and partial cross sections for breakup of ground rovibronic state of H + 2 by photon impact are calculated using the exact nonadiabatic nonrelativistic Hamiltonian without approximation. The converged results span six orders of magnitude. The breakup cross section is divided into dissociative excitation and dissociative ionization. The dissociative excitation channels are divided into contributions from principal quantum numbers 1 through 4. For dissociative ionization the fully differential cross section is calculated using a formally exact expression. These results are compared with approximate expressions. The Born-Oppenheimer expression for the dissociative ionization amplitude is shown to be deficient near onset. A Born-Oppenheimer approximation to the final state is shown to give accurate results for kinetic energy sharing, the doubly differential cross section, between the electronic and internuclear degrees of freedom. To accurately calculate the triply differential cross section, including the angular behavior, it is shown that nonadiabatic wave functions for both initial and final states are required at low electron energies.

Qualitative failure of a multiconfiguration method in prolate spheroidal coordinates in calculating dissociative photoionization ofH2+

“…In this figure the present results are compared with an exact numerical treatment using the full grid in the electronic coordinates and bond length, and with the Born-Oppenheimer approximation at the equilibrium bond length of 2a 0 . As already mentioned, such exact results have previously been reported by us [61] and more recently in Ref. [62].…”

“…As in Ref. [61], we additionally compare the results of the Chase approximation [69] which entails a convolution of the Born-Oppenheimer result over the wave packets of the initial and final vibrational states,…”

“…The dissociative ionization and dissociative excitation cross sections were recently calculated using numerically exact methods within the nonrelativistic approximation and reported in Refs. [61] (including non adiabatic couplings) and [62] (in the Born-Oppenheimer approximation). The effect of the nonadiabatic coupling terms in the Hamiltonian was analyzed in Ref.…”

“…The effect of the nonadiabatic coupling terms in the Hamiltonian was analyzed in Ref. [61]. Among other things, it was found that the doubly differential cross section (differential with respect to kinetic energy of the electron) is accurately calculated using a Born-Oppenheimer final state wave function, but is incorrect near onset when calculated with a Born-Oppenheimer initial state wave function.…”

A pump–probe scheme with a single chirped pulse to image electron and nuclear dynamics in molecules

“…We use atomic units unless otherwise stated. The theoretical description of the hydrogen molecular ion has been achieved in previous works employing cylindrical [28,29] or prolate spheroidal coordinates [30][31][32][33][34]. For the numerical respresentation of the molecular wave function, we here employ a single-center expansion using spherical harmonics, Y r l m ( ) to treat the angular degrees of freedom of the electron and a discrete variable representation combined with a finite element method (DVR) for the radial part of both the electronic (f i (r)) and nuclear (χ j (R)) components of the wave packet.…”