Nonadiabatic Nuclear Dynamics after Valence Ionization of H₂O

Abstract

The gas-phase photoelectron spectrum of water in the 12-20 eV energy range is simulated. The potential energy surfaces (PESs) of the three cationic states involved show several degeneracies. The ground state (X(2)B(1)) and the first excited state (A(2)A(1)) are degenerate components of a (2)Pi(u) state in linear geometry leading to Renner-Teller coupling while the PESs of the A state and the second excited state (B(2)B(2)) exhibit a conical intersection. Thus, an adiabatic approach that relies on sufficiently separated surfaces deems inappropriate. However, an orthogonal transformation of the electronic states removes the diverging matrix elements in the kinetic energy. These diabatic states permit a correct treatment of the nuclear dynamics near a conical intersection as well as in the Renner-Teller zone. The quantum mechanical equations of motion of the nuclei are solved using the multiconfiguration time-dependent Hartree (MCTDH) method. Quantum chemical calculations for the cationic states had been performed before, using a multireference configuration interaction method.

Toward a description of electron-induced dissociative excitation in H2O+ : Investigation of three resonances above the BRabadán1, Gorfinkiel2 2021Phys. Rev. A4070View full textAdd to dashboardCite

“…We start our description and discussion of results by presenting the elastic and inelastic cross sections at the equilibrium geometry of H 2 O + (X ): we locate the lowest resonances above theB state of H 2 O + that could be reached in electron collisions with H 2 O + (X ).B is the third electronic state of H 2 O + and appears as a broad band, made of broad vibrational peaks, in the photoelectron spectra of H 2 O [28], which points to the predissociating character of most of its vibrational states.…”

Nonadiabatic fragmentation of H2O+ and isotopomers. Wave packet propagation using ab initio wavefunctions

“…4,5 It can be formed in collisions of electrons, ions or photons with H 2 O and, given the importance of this molecule, many works have studied its ionization, and the ensuing dynamics of the remaining cation. Several experimental [6][7][8] and theoretical 9,10 works have addressed the photoionization of H 2 O with photon energies below 21.2 eV. At these energies, the photoelectron spectrum shows three bands that correspond to the formation of H 2 O + in the electronic states X 2 B 1 (hereafter denoted X), Ã 2 A 1 (Ã) and B 2 B 2 (B).…”

High-resolution photoelectron-spectroscopic investigation of the H2O+ cation in its electronic state

“…This degeneracy is lifted by the Renner-Teller effect as soon as the molecule bends, the coupling being mediated by the bending mode ν + 2 . This pair of states and the vibronic interaction between them have been the object of extensive work, both experimental [1][2][3][4][5][6][7][8][9][10][12][13][14] and theoretical [15][16][17][18][19]. The most extensive set of high-resolution spectroscopic information on the X+ and Ã+ states of H 2 O + have been obtained from spectra of the Ã+ − X+ band system in the visible and near infrared ranges of the electromagnetic spectrum [1,3,10,11].…”