Four-photon dissociation and ionization ofH2

Abstract

We report a quantitative investigation of competition between dissociation and ionization in four-photon excited Hz. The C 'II"v =0-4, N=1 -3 states are prepared by three-photon excitation from the ground state. Absorption of a fourth photon from the same laser pulse leads either to H2++e or H+H(n =3,4). This branching is monitored in photoelectron spectra, taken with a novel magnetic bottle electron spectrometer based on a permanent magnet design. The competition between dissociation and ionization shows a pronounced dependence on the symmetry, vibrational, and rotational quantum numbers of the C state. We attempt to explain this dependence in terms of excitation of dissociative H& states in the H2+ ionization continuum from which both autoionization and dissociation may occur.

Photoionization and photodissociation dynamics of H2 after (3+1) resonance-enhanced multiphoton ionization via the B 1Σu+ state

“…However, these higher H 2 ϩ yields can be explained by the observation that the R(1) transitions to the vЈϭ14 and 16 levels are nearly coincident with the three-photon transitions to the C 1 ⌸ u (1s g )(2p u ) vЈϭ3 and 4 levels, respectively. As demonstrated previously 11,14 and confirmed by the present experiments, one-photon absorption from the C 1 ⌸ u state leads predominantly to molecular photoionization, with the dissociation pathway playing only a very minor role. The ''slow'' photoelectrons observed for vЈϭ14 and 16 should consequently be attributed to molecular photoionization via the C 1 ⌸ u state, while the excited hydrogen atoms result predominantly from excitation of the B 1 ⌺ u ϩ state.…”

Photodissociation dynamics of doubly excited Rydberg states of molecular hydrogen

“…In other experiments, H + formation has been observed in the multiphoton excitation of H2 via the B I~u+ (Refs. 4,6,9,13), B' I~u+ (Ref. 7), C Illu (Refs.…”

“…Photoelectron kinetic energy analyses of both the Ht parent and H + fragment ions produced in multiphoton excitation schemes via the B I~u+ (Refs. 4,6,9,13) and C Illu (Refs. 6,8,16) states have provided the most insight into this problem.…”

Spectroscopic study of the second 3Πg state of H2 : A bound triplet state perturbed by a doubly excited state

“…(1) and (2) is equal to the amplitude of the difference (double-resonance) spectrum. In the Ionization + Dissociation limit where each laser depletes a small fraction of the neutral beam, this difference may be expressed as (3) wherefd 1 is the fraction of the neutral current No that laser I would, if acting alone, deplete by dissociation and is constant throughout the scan; 1.2 (v 2 ) is the fraction of neutral current that laser II would, acting alone, convert into ion current, and is dependent on the frequency of laser II. As a result, the difference spectrum exhibits features that reveal levels ionized by the tunable laser.…”