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

Abstract

We have performed a coupled electron−nuclear dynamics study of H 2 + molecular ions under the influence of an intense few-cycle 4.5 fs laser pulse with an intensity of 4 × 10 14 W/ cm 2 and a central wavelength of 750 nm. Both quantum and classical dynamical methods are employed in the exact similar initial conditions with the aim of head-to-head comparison of two methodologies. A competition between ionization and dissociation channel is explained under the framework of quantum and classical dynamics. The origin of the electron localization phenomena is elucidated by observing the molecular and electronic wave packet evolution pattern. By probing with different carrier envelope phase (CEP) values of the ultrashort pulse, the possibility of electron localization on either of the two nuclei is investigated. The effects of initial vibrational states on final dissociation and ionization probabilities for several CEP values are studied in detail. Finally, asymmetries in the dissociation probabilities are calculated and mutually compared for both quantum and classical dynamical methodologies, whereas Franck−Condon averaging over the initial vibrational states is carried out in order to mimic the existing experimental conditions.

Virtual Special Issue on Attosecond Chemistry

“…They show that the molecular structure is imprinted onto the elliptic-dichroism parameter for both monochromatic and bichromatic driving fields, so that it can be used as a tool to analyze the electron dynamics in molecules. Pandey et al present a theoretical study of the coupled electron–nuclear dynamics in the H 2 + molecular ion under the influence of an intense laser field, using both quantum and classical dynamical methods to analyze the validity of simpler classical methods for the description of strong-field phenomena involving both electronic and nuclear motions . Labeye et al have investigated the ultrafast vibronic dynamics triggered by intense femtosecond infrared pulses in small molecules .…”

“…Pandey et al present a theoretical study of the coupled electron−nuclear dynamics in the H 2 + molecular ion under the influence of an intense laser field, using both quantum and classical dynamical methods to analyze the validity of simpler classical methods for the description of strong-field phenomena involving both electronic and nuclear motions. 14 Labeye et al have investigated the ultrafast vibronic dynamics triggered by intense femtosecond infrared pulses in small molecules. 15 They provide a new interpretation of the observed nuclear wave packet dynamics and reveal intricate features in the fieldinduced nuclear motion that are not accounted for by existing models.…”

Attosecond Probing of Nuclear Vibrations in the D2+ and HeH+ Molecular Ions

“…In general, physical chemistry and chemistry can greatly benefit from these developments because new possibilities to steer and observe chemical reactions may arise in the future. 55,56 The Nobel Prize in Physics 2023 was awarded to Pierre Agostini, Ferenc Krausz, and Anne L'Huillier for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter. 57 The duration of the light pulses applied for probing and control purposes is of crucial importance regarding the applicability of the mapping or control scheme under consideration.…”

“…Attosecond science has given access to the natural time scale of electronic and fast nuclear motion. − Light pulses with subfemtosecond duration are now routinely generated in high-harmonic generation sources and X-ray-free electron lasers. In general, physical chemistry and chemistry can greatly benefit from these developments because new possibilities to steer and observe chemical reactions may arise in the future. , The Nobel Prize in Physics 2023 was awarded to Pierre Agostini, Ferenc Krausz, and Anne L’Huillier for experimental methods that generate attosecond pulses of light for the study of electron dynamics in matter…”

Efficient Control of Electron Localization and Probability Modulation with Synthesized Two-Color Intense Laser Pulses

“…On the other hand, for the study of both electronic and nuclear dynamics with unprecedented spatial as well as temporal resolution imaging of electron wavepacket, ultrashort strong laser pulses are currently regularly utilized. − Ever since the production of attosecond pulses, − the horizon of attosecond science has expanded gradually due to routine generation of such pulses with the aid of higher harmonic generation sources and X-ray-free electron lasers. − Indeed, attosecond pulses are widely used to the direct observation and control of the electrons and electronic wavepackets along with probing of molecular dipoles in attosecond domain, − since the time scale of such pulses match the natural time scale of electronic motion in molecules. , It is noteworthy that Agostini, Krausz, and L’Huillier were awarded the Nobel Prize in Physics 2023 for developing the experimental methods to generate attosecond pulses for studying electron dynamics. In this regard, normalH 2 + , being the simplest, yet most important prototype system for laser-induced molecular fragmentation process, is usually the extensively studied molecular system to understand the complex process of coupled electron–nuclear dynamics, − in particular under the influence of intense laser pulses. On the other hand, for a few-cycle pulse, the carrier-envelope phase (CEP) acts as an important controlling knob for electronic motions, where for the case of normalH 2 + , the electron can preferentially stick to either one of the two protons − due to the interference of odd and even photon number pathways as inspected by a lot of experimental − ,, as well as theoretical −…”