Quantum dynamics, isotope effects, and power spectra of H2+ and HD+ excited to the continuum by strong one-cycle laser pulses: Three-dimensional non

Strong Laser Field-Driven Coupled Electron–Nuclear Dynamics: Quantum vs Classical Description

“…In our present case, since the nuclei are restricted to move only along the polarization vector of the strong laser electric field, exclusion of molecular rotations seems to be a reasonably good assumption at first place. 45,48,79 This is consistent with the fact that the molecular rotation time scale (T rot ∼ 1/B e ∼ 10 4 , with B e being the rotational constant of the H 2 + molecule) is much larger than the time scales for the occurrence of ionization and dissociation processes initiated due to laser pulses with intensities above ∼10 13 W/cm 2 , more so for ultrashort laser pulses, where the interaction between molecule and the electric field can be regarded as "sudden" in comparison to rotation of the system. 34,80 Although incorporation of rotational−vibrational coupling phenomena originated due to the light-induced conical intersections effect 81,82 can have strong impact on the dissociation dynamics of H 2 + , we have excluded the molecular rotations, while the nuclei are free to move along the polarization direction of the laser electric field, and electrons move in three dimensions with conservation of cylindrical symmetry.…”

“…On a different note, Roudnev and Esry, in their theoretical study, proposed that CEP effects arise because of the superposition of electronic states with different parities, which, in turn, indicates that the CEP dependence is a quantum mechanical phenomenon. Understanding of such CEP-dependent coupled dynamics needs a fully quantum mechanical treatment , and requires the observation of both electronic and nuclear wave packet dynamics, simultaneously. − Indeed, during the interaction of a strong laser field, the dissociation and ionization phenomena occur concurrently , by following different pathways, where several control schemes were proposed to control as well as explain the electron localization phenomena. ,,, Due to this nonseparability of coupled electronic and nuclear degrees of freedom, − the solution of the time-dependent Schrödinger equation (TDSE) becomes extremely expensive, even for a one-electron system, for example, H 2 + , which requires propagation of both electronic and nuclear wave packets altogether. ,− To overcome the huge computational cost in quantum dynamics, alternate and computationally less-expensive methods based on classical mechanics had also been proposed in recent years, which have been able to successfully interpret several strong field experiments for atoms and molecules. ,− In the recent past, quasi-classical trajectory-based models − were employed to study the molecular double-ionization phenomena of molecules under the influence of intense laser fields, and also, some semiclassical theoretical methods , were used for studying electron collision–recollision dynamics and generation of higher order harmonics. Apart from the advantage in computational efficiency, trajectory-based classical models provide relatively easy interpretation of the observable by the back analysis of individual trajectories.…”

Controlling strong-field fragments of HD+ with a synthesized two-color laser pulse

“…In ref. 13 and 38–41, the simulation results indicated that the electron localization on the dissociation process of HD + can be controlled by manipulating the laser intensity, pulse duration and the CEP of the ultrashort femtosecond pulse. Subsequently, the schemes of two femtosecond laser pulses 42–44 have been employed to explore the possibility of controlling the branching ratio to different dissociation channels of HD + by tuning the laser frequency and delay time of the two femtosecond pulses.…”

Approximation Schemes to Include Nuclear Motion in Laser-Driven Ab Initio Electron Dynamics: Application to High Harmonic Generation

“…The quantum treatment of coupled electronic and nuclear motion has been accomplished for very small molecules, like H 2 + or related species, by numerically solving the molecular time-dependent Schrödinger equation on extended grids, among other things also in order to describe HHG. ,,− The general attention, however, has shifted from small molecules ,− to larger ones − recently. Chemically interesting molecules beyond H 2 + or alike are out of reach for the full solution of the coupled nuclear-electronic time-dependent Schrödinger equations.…”