Photodissociation as a probe of the H ₃ ⁺ avoided crossing seam

Abstract

Experiments are conducted to investigate the role of the avoided crossing seam in the photodissociation of H + 3 . Three-dimensional imaging of dissociation products is used to determine the kinetic energy release and branching ratio among the fragmentation channels. Vibrational distributions are measured by dissociative charge transfer of H + 2 products. It is found that the photodissociation of hot H + 3 in the near ultraviolet produces cold H + 2 , but hot H2. Modelling the wavepacket dynamics along the repulsive potential energy surface accounts for the repopulation of the ground potential energy surface. The role of the avoided crossing seam is emphasized and its importance for the astrophysically relevant charge transfer reactions is underlined.

Charge Transfer Processes for H + H2+ Reaction Employing Coupled 3D Wavepacket Approach on Beyond Born–Oppenheimer Based Ab Initio Constructed Diabatic Potential Energy Surfaces

“…It may be noted that this atom-ion charge transfer reaction is not extensively studied theoretically, whereas the experimental measurement of the rate constant was done by Karpas et al using the ion-cyclotron resonance (ICR) technique. Recently, experimental studies of the UV photodissociation of H 3 + to atom–diatom fragments were conducted by Urbain et al, which again signifies the role of the avoided crossing seam of the H 2 + + H reaction in an astrophysical context. However, to the best of our knowledge, there have not been any experiments for measuring the integral cross sections for such a process of this reaction over any energy range.…”

Hydrogen molecular ions: H 3 + , H 5 + and beyond

“…The H + 3 system itself has facets in its near-dissociation region that merit further investigation, including its near-dissociation spectrum, the possible presence of a whole series of weakly bound, long-range vibrational states [82] and exploring the nature of the H + 3 potential energy surface in the region above dissociation. In this region, there is interaction between surfaces which correlate with the two lowest dissociation asymptotes, H 2 + H + and H + 2 + H. The seam between these surfaces is now being probed using both photon processes and charge exchange; see Urbain et al [83]. Modelling these studies will require the extension of the accurate, global ground potential H + 3 potential energy surface [84,85] to forms which give multiple surfaces [86] accurately.…”

Unveiling Quantum Interference in the D+ + H2 Nonadiabatic Reaction Dynamics at Low Collision Energies

“…The H 3 + reaction system and its isotopic variants have been intensively studied theoretically and experimentally in the past decades. − One reason is that H 3 + plays a pivotal role in many astrochemical environments, − including interstellar clouds, planetary ionospheres, as well as the formation of stars. Therefore, the study of the corresponding reactive collisions is of great significance for understanding the chemical features of the interstellar medium.…”