arXiv subjects

Jean-Nicolas Vigneau

Publications and source records attributed to Jean-Nicolas Vigneau.

4 recordsLinked to original sources

arXiv2024

Electro-nuclear dynamics of single and double ionization of H$_2$ in ultrafast intense laser pulses

We present an efficient method for modeling the single and double ionization dynamics of the H$_2$ molecule in ultrashort intense laser fields. This method is based on a semi-analytical approach to calculate the time-dependent single and double molecular ionization rates and on a numerical approach to describe the vibrational motion that takes place in the intermediate molecular ion H$_2^+$. This model allows for the prediction of the single and double ionization probabilities of the H$_2$ molecule to be made over a wide range of frequencies and laser intensities with limited computational time, while providing a realistic estimate of the energy of the products of the dissociative ionization and of the Coulomb explosion of the H$_2$ molecule. The effect of vibrational dynamics on ionization yields and proton kinetic energy release spectra is demonstrated and, in the case of the latter, discussed in terms of basic strong-field molecular fragmentation mechanisms.

quant-ph↗

arXiv2022

Strong Field Non-Franck-Condon Ionization of H$_2$: A Semi-Classical Analysis

Single ionization of H$_2$ molecules exposed to strong and short laser pulses is investigated by a semi-classical method. Three laser characteristics are considered: i) The carrier-wave frequency corresponds to wavelengths covering and bridging the two ionization regimes: From tunnel ionization (TI) at 800 nm to multiphoton ionization (MPI) at 266 nm. ii) Values of the peak intensity are chosen within a window to eliminate competing double ionization processes. iii) Particular attention is paid to the polarization of the laser field, which can be linearly or circularly polarized. The results and their interpretation concern two observables, namely the end-of-pulse total ionization probability and vibrational distribution generated in the cation H$_2^+$. The most prominent findings are an increased ionization efficiency in circular polarization and a vibrational distribution of the cation that favors lower-lying levels than those that would be populated in a vertical (Franck-Condon) ionization, leading to non Franck-Condon distributions, both in linear and circular polarizations.

physics.atom-ph↗

arXiv2022

Strong-Field Molecular Ionization Beyond The Single Active Electron Approximation

The present work explores quantitative limits to the Single-Active Electron (SAE) approximation, often used to deal with strong-field ionization and subsequent attosecond dynamics. Using a time-dependent multi\-configuration approach, specifically a Time-Dependent Configuration Interaction (TDCI) method, we solve the time-dependent Schr{ö}dinger equation (TDSE) for the two-electron dihydrogen molecule, with the possibility of tuning at will the electron-electron interaction by an adiabatic switch-on/switch-off function. We focus on signals of the single ionization of $H_2$ under a strong near-infrared (NIR) four-cycle, linearly-polarized laser pulse of varying intensity, and within a vibrationally frozen molecule model. The observables we address are post-pulse total ionization probability profiles as a function of the laser peak intensity. Three values of the internuclear distance R taken as a parameter are considered, R = R$_{eq}$ = 1.4 a.u, the equilibrium geometry of the molecule, R = 5.0 a.u for an elongated molecule and R = 10.2 a.u for a dissociating molecule. The most striking observation is the non-monotonous behavior of the ionization probability profiles at intermediate elongation distances with an instance of enhanced ionization and one of partial ionization quenching. We give an interpretation of this in terms of a Resonance-Enhanced-Multiphoton Ionization (REMPI) mechanism with interfering overlapping resonances resulting from excited electronic states.

physics.atom-ph↗

arXiv2022

ATP Synthase: A Moonlighting Enzyme with Unprecedented Functions

ATP synthase's intrinsic molecular electrostatic potential (MESP) adds constructively to, and hence reinforces, the chemiosmotic voltage. This ATP synthase voltage represents a new free energy term that appears to have been overlooked. This term is at least roughly equal in order of magnitude and opposite in sign to the energy needed to be dissipated as a Maxwell's demon (Landauer principle).

physics.bio-ph↗