Precise description of single and double ionization of hydrogen molecule in intense laser pulses

Abstract

A new simulation box setup is introduced for the precise description of the wavepacket evolution of two electronic systems in intense laser pulses. In this box, the regions of the hydrogen molecule H(2), and singly and doubly ionized species, H(2) (+) and H(2) (+2), are well discernible and their time-dependent populations are calculated at different laser field intensities. In addition, some new regions are introduced and characterized as quasi-double ionization and their time-dependencies on the laser field intensity are calculated and analyzed. The adopted simulation box setup is special in that it assures proper evaluation of the second ionization. In this study, the dynamics of the electrons and nuclei of the hydrogen molecule are separated based on the adiabatic approximation. The time-dependent Schrödinger and Newton equations are solved simultaneously for the electrons and the nuclei, respectively. Laser pulses of 390 nm wavelength at four different intensities (i.e., 1 × 10(14), 5 × 10(14), 1 × 10(15), and 5 × 10(15) W cm(-2)) are used in these simulations. Details of the central H(2) region are also presented and discussed. This region is divided into four sub-regions related to the ionic state H(+)H(-) and covalent (natural) state HH. The effect of the motion of nuclei on the enhanced ionization is discussed. Finally, some different time-dependent properties are calculated, their dependencies on the intensity of the laser pulse are studied, and their correlations with the populations of different regions are analyzed.

High harmonic generation from pre-ionized H2in ultrashort intense laser fields

“…For this solution, we adopt a partitioning scheme for the simulation box which has been introduced and applied in our previous works [25,26]. This simulation box is shown in Fig.…”

“…In the work reported by Ruiz et al on the hydrogen molecule, the electron motion is included in its full dimensionality, while the center-of-mass motion is restricted along the polarization axis, and the system exhibited a rich double ionization quantum dynamics in the direction transversal to the field polarization [6]. However, most computations are carried out with some approximations in the dimensions of the electron, and in the nuclear dynamics [24][25][26][27][28]. In these studies of the interaction of the intense laser pulse with the hydrogen molecule, the electronic and nuclear dynamics have been considered in one dimension approximated by soft-core potential and classical mechanics, respectively [24][25][26][27].…”

“…However, most computations are carried out with some approximations in the dimensions of the electron, and in the nuclear dynamics [24][25][26][27][28]. In these studies of the interaction of the intense laser pulse with the hydrogen molecule, the electronic and nuclear dynamics have been considered in one dimension approximated by soft-core potential and classical mechanics, respectively [24][25][26][27]. In a recent work, the nuclear dynamics in one dimension has been treated quantum mechanically [28].…”

“…In our recent works, details of the dynamics of electrons and nuclei in the hydrogen molecule have been studied [25,26]. We introduced in [25] a new simulation box setup for the precise description of the evolution of two electronic systems in intense laser pulses based on which different regions of the hydrogen molecule are well discernible.…”

“…We introduced in [25] a new simulation box setup for the precise description of the evolution of two electronic systems in intense laser pulses based on which different regions of the hydrogen molecule are well discernible. In [25], details of the pre-ionization hydrogen molecule are studied and the underlying mechanisms responsible for the formation and evolution of the homolytic and ionic transient species are explored. We investigated in [26] contribution of the homolytic…”