V. K. Dolmatov

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Papers by V. K. Dolmatov

“Reading” the photoelectronβ-parameter spectrum in a resonance region

Physical Review A, 2007

The behavior of the dipole photoelectron angular distribution parameter ␤ nl ͑͒ in the vicinity o... more The behavior of the dipole photoelectron angular distribution parameter ␤ nl ͑͒ in the vicinity of autoionizing resonances is discussed. It is shown that from this behavior, surprisingly, many photoionization parameters that cannot be measured experimentally can be extracted. These are the energy positions and ordering of autoionizing resonance minima in the partial photoionization cross sections l+1 and l−1 , the energies at which these two cross sections intersect, and signs and magnitudes of the cos͑␦ l+1 − ␦ l−1 ͒ ͑␦ l±1 being the phase shifts of the dipole photoionization amplitudes D l±1 , respectively͒ through the autoionizing resonance energy region. Based on this, a deeper interpretation of such effects as the width-narrowing, width-fluctuating, and q-reversal in the ␤ nl parameter spectrum in the autoionizing resonance energy region is given. As an example, calculated data for partial photoionization cross sections 3d→f and 3d→p , and ␤ 3d parameters for 3d photoelectrons from Cr + are presented.

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Overlapping resonances in the β-parameter spectrum

Symmetry reversals and fluctuations of both width and intensity have so far been regarded photoab... more Symmetry reversals and fluctuations of both width and intensity have so far been regarded photoabsorption spectroscopy. It is demonstrated for the first time that they can also appear in the β-parameter spectrum, which then becomes generally different in appearance from the corresponding photoionization spectrum. Indeed, not only the location of the symmetry reversals, but even their number within a series differ between both spectra, and intensity fluctuations present in one spectrum can be absent from the other. Our study is performed within the `spin-polarized\u27 random-phase approximation with exchange

$Research paper thumbnail of On the 3p photoabsorption cross section of free mn\u3csup\u3e+\u3c/sup\u3e$

On the 3p photoabsorption cross section of free mn\u3csup\u3e+\u3c/sup\u3e

Multielectron calculations for the 3p photoabsoiplion cross section of free Mn+(3p63d54s7S) are p... more Multielectron calculations for the 3p photoabsoiplion cross section of free Mn+(3p63d54s7S) are performed for the first time. The essential influence of a strong mixing between the 3p-›4s and giant 3p-›3d resonances on the 3p absorption cross section is discovered. Theoretical arguments that the available experimental data for the Mn+ 3p absorption spectrum could belong not to the ‘pure’ Mn+ absorption but to the mixed absorption of Mn+, excited Mn+ ion and neutral Mn atom are put forward. © 1993 IOP Publishing Ltd

Positron elastic scattering by a semifilled-shell atom*

Journal of Physics B: Atomic, Molecular and Optical Physics, 2021

We theoretically study the positron elastic scattering by an atom with a multielectron semifilled... more We theoretically study the positron elastic scattering by an atom with a multielectron semifilled subshell in its structure. We focus on gaining the initial insight into the specifics of such a process. The positron scattering by the Mn(…3d54s2, 6S) atom with a 3d5 semifilled subshell (e+ + Mn scattering) is chosen as a case study. We account for both the electron correlation and the formation of a e+ + e− virtual positronium (Ps) in the intermediate states of the e+ + Mn system. Electron correlation is taken into account in the framework of the self-energy part of the scattering positron Green function generalized for the application to semifilled-shell atoms. The influence of the virtual Ps formation on the positron scattering is taken into account by the reduction of the energy of the virtual positron plus atomic-excited-configuration states by the Ps-binding energy, to a reasonable approximation. We unravel the importance and specificity of the influence of both the virtual Ps a...

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Effects of relativistic interactions in photodetachment time delay of Br−

Journal of Physics: Conference Series, 2020

Synopsis Wigner time delay in photodetachment of Br− has been studied. The absence of Coulomb pha... more Synopsis Wigner time delay in photodetachment of Br− has been studied. The absence of Coulomb phase in photodetachment process makes the Wigner time delay more sensitive to the centrifugal barrier shape resonance and threshold effects. Important relativistic effects have been found near the threshold region.

Wigner–Eisenbud–Smith photoionization time delay due to autoioinization resonances

Journal of Physics B: Atomic, Molecular and Optical Physics, 2018

An empirical ansatz for the complex photoionization amplitude and Wigner–Eisenbud–Smith time dela... more An empirical ansatz for the complex photoionization amplitude and Wigner–Eisenbud–Smith time delay in the vicinity of a Fano autoionization resonance are proposed to evaluate and interpret the time delay in the resonant region. The utility of this expression is evaluated in comparison with accurate numerical calculations employing the ab initio relativistic random phase approximation and relativistic multichannel quantum defect theory. The indisputably good qualitative agreement (and semiquantitative agreement) between corresponding results of the proposed model and results produced by the ab initio theories proves the usability of the model. In addition, the phenomenology of the time delay in the vicinity of multichannel autoionizing resonances is detailed.

Relativistic calculations of angle-dependent photoemission time delay

Physical Review A, 2016

Angular dependence of photoemission time delay for the valence np 3/2 and np 1/2 subshells of Ar,... more Angular dependence of photoemission time delay for the valence np 3/2 and np 1/2 subshells of Ar, Kr and Xe is studied in the dipole relativistic random phase approximation. Strong angular anisotropy of the time delay is reproduced near respective Cooper minima while the spin-orbit splitting affects the time delay near threshold.

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Relativistic effects in photoionization time delay near the Cooper minimum of noble-gas atoms

Physical Review A, 2014

Time delay of photoemission from valence ns, np 3/2 and np 1/2 sub-shells of noble gas atoms is t... more Time delay of photoemission from valence ns, np 3/2 and np 1/2 sub-shells of noble gas atoms is theoretically scrutinized within the framework of the dipole relativistic random phase approximation. The focus is on the variation of time delay in the vicinity of the Cooper minima in photoionization of the outer sub-shells of neon, argon, krypton and xenon, where the corresponding dipole matrix element changes its sign while passing through a node. It is revealed that the presence of the Cooper minimum in one photoionization channel has a strong effect on time delay in other channels. This is shown to be due to inter-channel coupling.

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Suppression of the 3p→nd (n > 3) resonances in the 3p photoabsorption of free Mn and Mn+

Physics Letters A, 1993

Abstract The reasons for a weakly developed structure of the 3p→ n d ( n > 3) Rydberg series i... more

Controlling orbital collapse from inside and outside a transition element

Journal of Physics B: Atomic, Molecular and Optical Physics, 1998

ABSTRACT We report a study of bimodal behaviour of atomic wavefunctions for a transition element ... more ABSTRACT We report a study of bimodal behaviour of atomic wavefunctions for a transition element (Cr) and how this behaviour can be controlled and even turned into single-mode character either by (i) varying the effective nuclear charge for nonintegral values, or (ii) placing the atom in a spherical cavity of adjustable radius. Our conclusions have relevance to the emergence of valence instabilities for transition metals in the solid state. Also it is shown that the very existence of the bimodal wavefunctions provides an explanation for the frequently experienced instability of self-consistent field algorithms when a double-valley potential occurs, and suggestions are made on how to improve the numerical procedure for such calculations.

Giant resonance and Rydberg series of laser excited chromium atoms

AIP Conference Proceedings, 1995

ABSTRACT Theoretical and experimental photoelectron spectra of ground state and laser excited Cr ... more ABSTRACT Theoretical and experimental photoelectron spectra of ground state and laser excited Cr atoms in the region of the 3p-excitation are presented. The 3p↠4d,5d Rydberg excitations, which are very prominent in the 3d partial cross section of ground state Cr, and dramatically reduced by exciting the 4s electron into the 4p-shell. SPHF (spin polarized Hartree-Fock) calculations suggest that the well developed Rydberg series of ground state atoms are due to the delocalization of the 3d↓, 4d↓ and 5d↓ wavefunctions, whereas, the corresponding wavefunctions of laser excited Cr do not undergo such an anticollapse.

$Research paper thumbnail of Suppression of the 3p→nd (n \u3e 3) resonances in the 3p photoabsorption of free Mn and Mn\u3csup\u3e+\u3c/sup\u3e$

Suppression of the 3p→nd (n \u3e 3) resonances in the 3p photoabsorption of free Mn and Mn\u3csup\u3e+\u3c/sup\u3e

The reasons for a weakly developed structure of the 3p→nd (n \u3e 3) Rydberg series in the 3p abs... more

$Research paper thumbnail of On the e\u3csup\u3e-\u3c/sup\u3e - C60 elastic angle-differential scattering cross section$

On the e\u3csup\u3e-\u3c/sup\u3e - C60 elastic angle-differential scattering cross section

© 2020 Institute of Physics Publishing. All rights reserved. We study theoretically the experimen... more © 2020 Institute of Physics Publishing. All rights reserved. We study theoretically the experimental angle-differential elastic electron scattering off a C60 fullerene with the aim to elucidate whether its features depend primarily on the details of the full molecular potential of C60 or they can be understood without reference to the full nature of the potential. We demonstrate the success of the latter option

$Research paper thumbnail of Trends in valence autoionizing Rydbergs for nd\u3csup\u3e5\u3c/sup\u3e semifilled-shell ground and excited atoms and ions: Cr, Mn, Mn\u3csup\u3e+\u3c/sup\u3e, Fe\u3csup\u3e+\u3c/sup\u3e, Fe\u3csup\u3e2+\u3c/sup\u3e, Mo, Tc, Tc\u3csup\u3e+\u3c/sup\u3e and Re$

Trends in valence autoionizing Rydbergs for nd\u3csup\u3e5\u3c/sup\u3e semifilled-shell ground and excited atoms and ions: Cr, Mn, Mn\u3csup\u3e+\u3c/sup\u3e, Fe\u3csup\u3e+\u3c/sup\u3e, Fe\u3csup\u3e2+\u3c/sup\u3e, Mo, Tc, Tc\u3csup\u3e+\u3c/sup\u3e and Re

New regularities are reported for valence-shell autoionizing nd → n′p Rydbergs decaying to a cont... more New regularities are reported for valence-shell autoionizing nd → n′p Rydbergs decaying to a continuous spectrum of the (n + 1)sq valence subshell of free metal atoms and ions with nd5 semifilled subshells: Cr(3d54s17S), Mn(3d54s26S), Mn+(3d54s17S), Fe+(3d54s2 6S), Fe2+(3d54s17S), Mo(4d55s17S), Tc(4d55s26S), Tc+(4d55s17S) and Re(5d56s26S). We predict an extreme narrowing for the nd → n′p autoionizing Rydbergs in the nd5 atoms and ions with a ground-state nd5(n + 1)sq=17S valence-shell configuration. In contrast, incomparably broader Rydbergs occur in both atoms and ions with a ground configuration nd5(n + 1)sq=26S, or in metastable atoms and ions whose electron configuration is nd5 (n + 1)sq=15S. We also predict a drastic difference between the nd → n′p Rydberg profiles in partial (n + 1)s↑ and (n + 1)s↓, photoionization cross sections of the nd5 atoms and ions with a closed (n + 1)s2 valence subshell (arrows ↑ and ↓ show the two possible spin orientations for the ejected photoelect...

On possible multiple occurrences of the breakdown of the dipole and dipole-quadrupole approximations in angle-differential spectra of fullerene anions

We provide the initial insight into the angle-differential photodetachment spectra of fullerene a... more We provide the initial insight into the angle-differential photodetachment spectra of fullerene anions beyond the dipole approximation by utilizing a broadly used modelling of Cn. In the model, the Cn cage is approximated by a spherical attractive potential of a certain inner radius, thickness and depth which binds an external electron, thereby turning into a C − n anion. It is demonstrated in the framework of the utilized model, which a single-electron model in its essence, that the dipole and dipole-quadrupole approximations might get broken down in the angle-differential photodetachment spectra of fullerene anions, C − n , at a great number of photon energies of only a few tens of eV. Moreover, the breakdown occurrences are shown to start developing at lower photon energies, and the frequency of the occurrences grows with increasing size of C − n. The findings are demonstrated by direct calculations of angle-differential photodetachment cross sections of the C − 60 , C − 240 , C − 540 and C − 1500 anions. It is not clear beforehand how electron correlation might affect the predicted anomalies in the C − n angle-differential photodetachment spectra, so that the verification(s) of the predicted breakdowns by means of more sophisticated theories is urged.

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Polarization of the C60 cage by the photoelectron, interior static polarization of C60 by the ion-remainder and atomic-core relaxation in A@C60 photoionization

Photoionization cross sections, σ nℓ , photoelectron angular-asymmetry parameters, β nℓ , and pho... more Photoionization cross sections, σ nℓ , photoelectron angular-asymmetry parameters, β nℓ , and photoionization time delays, τ nℓ , for endohedral atoms, A@C60, are studied with account for both the individual and combined effects of dipole static polarization (DSP) of the C60 fullerene cage by the outgoing photoelectron, interior static polarization (ISP) of C60 by the ion-remainder, A + , and atomic-core relaxation of the encapsulated atom upon its ionization. It is unraveled by the direct calculations that the DSP effect is weak. It changes the phase of confinement-resonant oscillations in σ nℓ , β nℓ and τ nℓ without generally noticeable changes in their magnitudes, unless σ nℓ concentrates a relatively large part of oscillator strength of the continuum spectrum near threshold; then and there, the changes can be noticeable. This is counter-intuitive in view of a large dipole static polarizability of C60, α > 800 a.u.. Furthermore, it is demonstrated that the DSP effect results in the transmission of a part of oscillator strength of the continuum spectrum of A@C60 into its discrete spectrum. It is shown that the DSP effect is counteracted by ISP, thus getting partially cancelled out by the latter. Possible reasons behind the made findings are provided. Photoionization of Xe@C60, Ne@C60, H@C60 and some hypothetical C − 60 fullerene anions is chosen as a case study. For Xe@C60, the role of atomic-core relaxation of the ionized encapsuled Xe +-ion-remainder on the 4d photoionization of Xe@C60 is explored and detailed, and is revealed to be of utter significance, as in the known case of free Xe. The study is performed in the frameworks of both the random phase approximation with exchange (RPAE) and generalized RPAE (GRPAE), when needed. The C60 cage is modelled by a spherical attractive potential of a certain inner radius, thickness and depth. Its dipole static polarization potential is approximated by the Bates dipole static potential.

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Fission and Re-Ordering in Semifilled Shell Atoms

Alternate contraction and drastic expansion, i.e., 'breathing' of electronic subshells, the effec... more Alternate contraction and drastic expansion, i.e., 'breathing' of electronic subshells, the effects of fusion of two subshells into one subshell and its subsequent fission (splitting) into the original subshells, as well as multiple alteration of the order of subshells in confined semifilled shell atoms with a progressively narrowing confinement are theoretically discovered. The confinement is represented by a repulsive penetrable spherical potential of an inner radius r 0. The effects are exemplified by calculated data for confined semifilled shell atoms from the second, third and fourth rows of Mendeleev's table-Li, N, P and Cr atoms with semifilled 2s 1 , 2p 3 , 3p 3 and 3d 5 subshells, respectively-for the completeness of the study. The underlying physics behind the discovered effects is explained.

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Impact of nondipole effects on spin-polarization of photoelectrons from fullerene anions

Bulletin of the American Physical Society, 2017

Role of polarizability of a C N fullerene cage in A@C N photoionization and e−–C N scattering: the size effect

Journal of Physics B: Atomic, Molecular and Optical Physics, 2019

© 2019 IOP Publishing Ltd. We show that, in contradiction to intuitive perception, the impact of ... more © 2019 IOP Publishing Ltd. We show that, in contradiction to intuitive perception, the impact of polarization of a CN cage by the outgoing photoelectron on photoionization of a A@CN endohedral atom decreases as the size of CN increases. This is counter-intuitive, owing to the fact that the polarizability of CN drastically increases with the increase of N. Furthermore, we demonstrate that this is also in contrast to the polarization impact on elastic electron scattering off empty fullerenes; for the latter, the bigger the CN cage (the greater its polarizability), the greater the polarization impact is on the scattering process. We provide researchers with a \u27relative frame of reference\u27 for understanding how the increase in the size of the cage affects the polarization impact on the corresponding photoionization and electron scattering processes. Our findings are supported by the direct calculations of the photoionization and electron scattering cross sections for selected fullerene cages from \u27dwarf\u27 C20 to \u27giant\u27 C240. The calculations are performed in the framework of a semi-empirical modeling of CN and A@CN fullerene systems obtained with and without account for the dipole static polarizability of a fullerene cage

Angle-differential elastic-electron scattering off C 60: a simple semi-empirical theory versus experiment

Journal of Physics B: Atomic, Molecular and Optical Physics, 2019

We prove in the present paper that a simple modeling of a complicated highly polarizable C60 targ... more We prove in the present paper that a simple modeling of a complicated highly polarizable C60 target by a rectangular (in a radial coordinate) square well potential in combination with the static polarization potential provides a viable approximation for a low-energy elastic electron scattering off this target. The proof is based on the results of the comparison of the calculated angle-differential elastic electron scattering cross section off C60 versus corresponding experimental data.

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V. K. Dolmatov

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