arXiv subjects

Denys I. Bondar

Publications and source records attributed to Denys I. Bondar.

96 records · Page 6Linked to original sources

arXiv2010

Enhancement and suppression of tunneling by controlling symmetries of a potential barrier

We present a class of 2D systems which shows a counterintuitive property that contradicts a semi classical intuition: A 2D quantum particle "prefers" tunneling through a barrier rather than traveling above it. Viewing the one particle 2D system as the system of two 1D particles, it is demonstrated that this effect occurs due to a specific symmetry of the barrier that forces excitations of the interparticle degree of freedom that, in turn, leads to the appearance of an effective potential barrier even though there is no "real" barrier. This phenomenon cannot exist in 1D.

quant-ph↗

arXiv2009

An electron in the presence of multiple zero range potentials and an external laser field -- exact solutions for photoionization and stimulated bremsstrahlung

The method of zero range potential (ZRP) for one-electron problems is reviewed. In the absence of an external electromagnetic field, the notion of a ZRP is introduced from different points of view and for an arbitrary dimension of space. Then, three-dimensional problems of motion of an electron in the field of several ZRPs and laser radiation are studied. Exact wave functions for the processes of photoionization and stimulated bremsstrahlung in the presence of the laser field of an arbitrary pulse shape are obtained in the form of one-dimensional integral representations.

physics.atom-ph↗

arXiv2009

Photoelectron spectra in strong-field ionization by a high frequency field

We analyze atomic photoelectron momentum distributions induced by bichromatic and monochromatic laser fields within the strong field approximation (SFA), separable Coulomb-Volkov approximation (SCVA), and ab initio treatment. We focus on the high frequency regime -- the smallest frequency used is larger than the ionization potential of the atom. We observe a remarkable agreement between the ab initio and velocity gauge SFA results while the velocity gauge SCVA fails to agree. Reasons of such a failure are discussed.

physics.atom-ph↗

arXiv2009

Adaptation of the Modified Adiabatic Approximation to Strong Field Ionization

Savichev's modified adiabatic approximation [Sov. Phys. JETP 73, 803 (1991)] is used to obtain a general form of a quantum-mechanical amplitude of ionization by a low-frequency laser field. The method possesses only one requirement that the frequency of the laser field must be low. Connections of the obtained result with the quasi-classical approximation and other previous investigations are discussed.

physics.atom-ph↗

arXiv2009

Two-electron ionization in strong laser fields below intensity threshold: signatures of attosecond timing in correlated spectra

We develop an analytical model of correlated two-electron ionization in strong infrared laser fields. The model includes all relevant interactions between the electrons, the laser field, and the ionic core nonperturbatively. We focus on the deeply quantum regime, where the energy of the active electron driven by the laser field is insufficient to collisionally ionize the parent ion, and the assistance of the laser field is required to create a doubly charged ion. In this regime, the electron-electron and the electron-ion interactions leave distinct footprints in the correlated two-electron spectra, recording the mutual dynamics of the escaping electrons.

physics.atom-ph↗

arXiv2008

Instantaneous Multiphoton Ionization Rate and Initial Distribution of Electron Momenta

The Yudin-Ivanov formula [Phys. Rev. A 64, 013409 (2001)] is generalized such that the most general analytical expression for single-electron spectra, which includes the dependence on the instantaneous laser phase, is obtained within the strong field approximation. No assumptions on the momentum of the electron are made. Previously known formulas for single-electron spectra can be obtained as approximations to the general formula.

quant-ph↗