Theoretical Investigations of the Electronic and Nuclear Dynamics of Molecules in Intense Laser Fields: Quantum Mechanical Wave Packet Approaches

Abstract

We have developed a method for describing the reaction dynamics of a polyatomic molecule in intense laser fields. First, the dynamical behavior of H 2 þ and H 2 in near-infrared, intense laser fields (I > 10 13 W cm À2 and ! > 700 nm) was examined; accurate evaluation of the electronic and nuclear wave packet was achieved by the dual transformation method that we developed. Using ''field-following'' time-dependent adiabatic states defined as eigenfunctions of the ''instantaneous'' electronic Hamiltonian, we have clarified the dynamics of bound electrons, ionization processes, Coulomb explosion processes, and molecular vibrations of H 2 þ and H 2 . The analyses indicate that the multielectron dynamics and nuclear dynamics of polyatomic molecules in intense fields can be described by using the potential surfaces of time-dependent adiabatic states and the nonadiabatic coupling elements between those states. To obtain time-dependent adiabatic states of a molecule, one can diagonalize the electronic Hamiltonian including the interaction with the instantaneous laser electric field by ab initio molecular orbital (MO) methods. The time-dependent adiabatic potentials obtained are used to evaluate the multichannel nuclear dynamics until the next ionization process. We have applied the time-dependent adiabatic state approach to reveal the characteristic features of the dynamics of structural deformations of CO 2 and its cations in a near-infrared intense laser field. The experimentally observed stretched and bent structure of CO 2 3þ just before Coulomb explosions originates from the structural deformation of CO 2 2þ . We also revealed the mechanism of the experimentally observed bond dissociation of C 2 H 5 OH; we found that the relative probability of C-O bond cleavage to that of C-C bond cleavage becomes smaller with decreases in the pulse length. This example clearly shows that field-induced nonadiabatic transitions play a decisive role in the reaction dynamics of molecules in an intense laser field.

Quantum simulations of toroidal electric ring currents and magnetic fields in linear molecules induced by circularly polarized laser pulses

“…Refs. [14][15][16][17]. Recently, we could predict that ultrashort circularly polarized laser pulses induce unidirectional electron circulation or electric ring currents and associated magnetic fields in oriented planar molecules such as Mg-porphyrin [18,19].…”

Nonadiabatic orientation, toroidal current, and induced magnetic field in BeO molecules

“…On the subfemtosecond time scale, the vibrational modes are frozen, introducing an opportunity to trigger and directly probe electronic dynamics, [4][5][6][7][8][9][10][11][12][13] and coupled electron-nuclear dynamics. [14][15][16][17] An interesting example of electron dynamics in bound states of neutral molecules is unidirectional electron circulation, or electric ring currents, and associated magnetic fields, occurring in degenerate excited states that carry nonzero electronic angular momentum. Such currents have been numerically observed in atoms and ions, 18 in oriented linear molecules, 19,20 and in oriented aromatic molecules.…”

Molecular events in the light of strong fields: A light‐induced potential scenario

“…[110][111][112] More elaborate Hamiltonians and calculations exist. [113,114] In Figure 4 we show results of the actual dynamics obtained by solving Eq. (7) under a strong constant field 0 .…”