Toward a description of electron-induced dissociative excitation in H2O+ : Investigation of three resonances above the B

Abstract

Electron-induced dissociative excitation (DE) is a little studied process of significant applied relevance. Our aim is to provide a theoretical counterpart to earlier experiments [M.

Resonant Fragmentation of the Water Cation by Electron Impact: a Wave‐Packet Study

“…In this two-state simulation, the potential energy matrix, V, is diagonal; it stores the PESs calculated at the grid points. Since we consider electronic states of the neutral molecule and the cation, the non-adiabatic couplings between the two electronic states vanish, and it is not necessary to perform an adiabatic-to-diabatic transformation that would introduce off-diagonal matrix elements in V. To describe the autoionization, the potential energies of 2 3 A 00 determined in the R-matrix calculations [9] have an imaginary part related to the resonance lifetime.…”

“…In the simulation, the electronic energy of the resonant state 2 3 A 00 has been approximated by shifting that of the parent state of H 2 O + ( C 2 A 00 ) by À 0.2 hartree. This was determined to be a good approximation [9] to the resonant PES obtained from the R-matrix calculations using the UKRmol + suite. [17] This approximation is, in general, valid, except for some regions where the C 2 A 00 PES exhibits avoided crossings with other states of H 2 O + .…”

“…[1] OH radicals are also important in the Earth's atmosphere, where they clean the air by breaking down organic molecules. DR and DE in electron collisions with H 2 O + were studied in the ASTRID experiment of Jensen et al [2] In addition, DR was also investigated by Mul et al [3] and in CRYRING experiments [4][5][6] and DE by Fogle et al [7] The theoretical works are scarce: Nkambule et al [8] studied DR, and, more recently, Rabadán and Gorfinkiel [9] carried out R-matrix calculations [10] to characterize resonant states with energies of up to 13 eV above the X 2 A 00 ( X 2 B 1 in C 2v symmetry) state of H 2 O + at its equilibrium geometry. Molecular resonant states in that energy range include the complete Rydberg series converging to the à 2 A 0 ( à 2 A 1 ) and B 2 A 0 ( B 2 B 2 ) of H 2 O + and the low members of the Rydberg series converging to the dissociative cation states C 2 A 00 ( C 2 A 1 ), ã 4 A 00 (ã 4 B 1 ) and D 2 A 0 ( D 2 A 1 ).…”

“…Schematically, we start with a nuclear wave packet corresponding to the ground vibrational state of the H 2 O + cation in its ground electronic state X 2 A 00 . The colliding electron is captured by the molecular cation to form the resonant state of H 2 O (2 3 A 00 ), whose main [9] autoionization (AI) channel is the X 2 A 00 state. Therefore, the resonant state can decay through the reactions:…”

Theory of electronic resonances: Fundamental aspects and recent advances

“…• core-ionized states that undergo Auger decay, 7,70,71 • core-excited states that undergo resonant Auger decay, 72,75 • related species involving more than one molecule that decay through intermolecular Coulombic decay, 83,86 • anionic states formed by electron attachment to Rydberg states, [111][112][113] • superexcited Rydberg states, 107,[114][115][116] • states of high spin multiplicity that decay only by spin-orbit coupling. [117][118][119][120] Shape resonances can be easily understood in real coordinate space: The shape of the effective potential is responsible for the metastable nature of the resonance, meaning the electron is trapped behind a potential wall but it can leave the system by tunneling.…”