arXiv subjects

Maria M. Popova

Publications and source records attributed to Maria M. Popova.

5 recordsLinked to original sources

arXiv2026

Dynamics of electromagnetically induced water molecule fragmentation

The development of intense high-energy radiation sources and the improvement of techniques for detecting charged fragments have made possible experiments on multiple ionization of a molecule with registration of the momentum and charge of dissociation products in coincidence. This technique allows to determine (`fix') a molecular geometry at the time of fragmentation and called fixed-in-space molecule. In this work, the dynamics the water molecule dissociation fragments resulting from interaction with intense X-ray radiation has been studied. The charge distribution of oxygen ions was calculated, Newton diagrams were constructed for fragments - protons and the oxygen ion - for various charge states of the latter, and the released kinetic energy was evaluated. Calculations were performed using the [1]code for parameters close to [2]. The predictions for the different pulse parameters are done.

physics.atom-ph↗

arXiv2025

General properties of the RABBITT at parity mixing conditions

Parity mixing in photoionization, i.e. when emitted electrons have different parities but the same energy, causes interference observable only in angle-resolved measurements. The interference typically manifests as a symmetry violation in the photoelectron angular distributions. The traditional, based on HHG, RABBITT scheme with high-order harmonics separated by twice the seed field energy, precludes parity mixing. On the contrary, a free-electron laser provides a possibility to generate even harmonics. Using triple the fundamental frequency as a seed, one obtains a comb of alternating even and odd harmonics, separated by three times the initial frequency [Nature 578, 386-391 (2020)] (2-SB RABBITT). In this setup, there are two sidebands between the main photoelectron lines, versus one in the traditional scheme. In the paper, we examine the general properties of a two-sideband scheme and analyze the symmetry breakdown of photoelectron angular distributions for various polarization geometries of the incident pulse. We found a crucial difference in symmetries between 2-SB RABBITT and other photoionization schemes with parity mixing. Illustrative calculations are carried out for neon with pulse parameters typical for modern facilities. The possibility to reconstruct the temporal profile of the pulse from the angle-resolved measurements is discussed.

physics.atom-ph↗

arXiv2024

The Advantages of Polarization Control in RABBITT

The RABBITT setup is theoretically studied for various combinations of XUV and IR field components polarization: 'linear+linear', `linear+circular' with crossed propagation directions, and `circular+circular' with parallel propagation directions. The general properties of photoelectron angular distributions and their responses to the variation of the IR pulse delay are studied. Numerical simulations are performed for the neon valence shell ionization into the region of structureless continuum using two approaches based on time dependent perturbation theory and solution of rate equations. To distinguish between "geometrical" governed by fields' polarization and spectroscopic features, additional analysis for the case of $s$-shell ionization is presented.

physics.atom-ph↗

arXiv2022

Evolution of the ionic polarization in multiple sequential ionization: general equations and an illustrative example

The modern Free-Electron-Lasers generate a highly intense polarized radiation which initiate a sequence of ionization and decay events. Their probability depends on the polarization of each state as function of time. Its complete accounting is limited by the fact that a state can be formed in various ways. Here we present the equivalent of rate equations for population that completely accounts polarization of radiation and formulated in terms of the statistical tensors. To illustrate our approach we theoretically consider sequential photoionization of krypton by an intense extreme ultraviolet femtosecond pulse for the photon energies below the 3d-shell excitation threshold. The calculations of the ion yields, photoelectron spectra and ionic polarization for various photon fluence are presented and role of polarization is discussed.

physics.atom-ph↗

arXiv2020

A new method for measuring angle-resolved phases in photoemission

Quantum mechanically, photoionization can be fully described by the complex photoionization amplitudes that describe the transition between the ground state and the continuum state. Knowledge of the value of the phase of these amplitudes has been a central interest in photoionization studies and newly developing attosecond science, since the phase can reveal important information about phenomena such as electron correlation. We present a new attosecond-precision interferometric method of angle-resolved measurement for the phase of the photoionization amplitudes, using two phase-locked Extreme Ultraviolet pulses of frequency $ω$ and $2ω$, from a Free-Electron Laser. Phase differences $Δ\tilde η$ between one- and two-photon ionization channels, averaged over multiple wave packets, are extracted for neon $2p$ electrons as a function of emission angle at photoelectron energies 7.9, 10.2, and 16.6 eV. $Δ\tilde η$ is nearly constant for emission parallel to the electric vector but increases at 10.2 eV for emission perpendicular to the electric vector. We model our observations with both perturbation and \textit{ab initio} theory, and find excellent agreement. In the existing method for attosecond measurement, Reconstruction of Attosecond Beating By Interference of Two-photon Transitions (RABBITT), a phase difference between two-photon pathways involving absorption and emission of an infrared photon is extracted. Our method can be used for extraction of a phase difference between single-photon and two-photon pathways and provides a new tool for attosecond science, which is complementary to RABBITT.

physics.atom-ph↗