Strong Field Theories beyond Dipole Approximations in Nonrelativistic Regimes

Magnetic fields alter strong-field ionization

“…To deepen our understanding of the momentum transfer in recollision-free ionization with circularly polarized laser fields, we have developed a quantum-orbit model based on the strongfield approximation (SFA) as described in Ref. 3 In the simplest possible picture, the photoelectrons can be described in a two-step model consisting of (i) laser-induced tunnel ionization and (ii) potential-free acceleration of the electron as a ).…”

“…When a strong laser pulse induces the ionization of an atom, momentum conservation dictates that the absorbed photons transfer their momentum pγ = Eγ/c to the electron and its parent ion. Even after 30 years of studying strong-field ionization, the sharing of the photon momentum between the two particles and its underlying mechanism are still under debate in theory [1][2][3][4] . Corresponding experiments are very challenging due to the extremely small photon momentum (~10 -4 a.u.)…”

Theory of Subcycle Linear Momentum Transfer in Strong-Field Tunneling Ionization

“…Further theoretical studies [28][29][30] found that the photon momentum transferred in the tunneling step is not given entirely to the ion due to the action of the laser magnetic field, resulting in the final electron momentum in the laser propagation direction…”

“…where β denotes the fraction of the momentum transferred to the electron during the tunneling step. Estimates for the ground-state hydrogen atom vary between β ¼ 0.3 [28,29] and β ¼ 1=3 [29,30].…”

“…The simulation box is separated smoothly into an inner and an outer part by an absorbing boundary of the form 1=½1 þ expfðr − r 0 Þ=dg, where r 0 ¼ 164 and d ¼ 4 a:u: The inner part is propagated using the full Hamiltonian and the outer part using a Coulomb-free Hamiltonian. At each time step, the absorbed wave function is projected onto the nondipole Volkov solution [29,53] to incrementally obtain the momentum distribution [54,55]. Alternatively, the TDSE is also solved with the generalized pseudospectral method [56][57][58], where the time propagation of the nondipole contribution is treated using a Taylor expansion in combination with a split-operator method [40].…”