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

Abstract

The nonadiabatic fragmentation of excited water cations (and isotopomers) is studied by propagating wave packets on ab initio potential energy surfaces.

Toward a description of electron-induced dissociative excitation in H2O+ : Investigation of three resonances above the BRabadán1, Gorfinkiel2 2021Phys. Rev. ASelf Cite4070View full textAdd to dashboardCite

“…H 2 O + (Ã) has a dissociation energy of about 4.2 eV, which also rules out its contribution to fragmentation at 4 eV and below. On the other hand, H 2 O + (B), which only supports two bound vibrational levels, can easily dissociate above 0.3 eV via a conical intersection that populates statesà andX ; for energies above 2.7 eV, dissociation directly on theB PES is also possible [17].…”

“…The study of the PESs corresponding to the three resonances identified in the previous section has been carried out in the grid of points (set of geometries) used in Suárez et al [17]. This grid is defined in the Jacobi coordinates {R, r, θ} illustrated in Fig.…”

“…The resonance PESs are repulsive in the R and r coordinates around the equilibrium geometry of H 2 O + , so the capture of one electron into them will trigger the stretching of both O-H bonds. If the resonances decay into theB state, the remaining cation can dissociate as shown by Suárez et al [17], but if the resonance survives long enough to reach geometries where it can only decay intoà orX , then the dissociation of the cation will depend on the amount of electronic energy that is converted into nuclear kinetic energy.…”

“…The original set of geometries in Suárez et al [17] contained 278 382 points. Here, we choose a subset of these geometries for which the resonances are above stateB, as estimated using the fact that, as seen above, the positions of the resonances can, in general, be approximated by a small range of geometry-independent values of quantum defect.…”

“…Our results are presented in Sec. IV together with a discussion of the DE process that takes advantage of the recent studies by Suárez et al [16,17] on the fragmentation of theB state of H 2 O + . Finally, in Sec.…”