arXiv subjects

V. P. Popov

Publications and source records attributed to V. P. Popov.

11 recordsLinked to original sources

arXiv2022

Collision-induced radiative quenching and other disintegration modes of the $2S$ state of muonic hydrogen and deuterium atoms

The formation and various disintegration modes of $2s$ states for muonic hydrogen and deuterium atoms at kinetic energies both above and below the $2s-2p$ threshold are studied. The cross sections of the collision-induced radiative quenching, elastic scattering, and Coulomb deexcitation of $(μ^- p)_{2s}$ and $(μ^- d)_{2s}$ atoms in collisions with ordinary hydrogen and deuterium atoms at collision energies below the $2s-2p$ threshold are calculated in the framework of the close-coupling approach. The basis set includes all open and closed channels corresponding to exotic-atom states with principal quantum number $n$ from 1 up to 30. Results of these numerical quantum-mechanical calculations of cross sections are used as input data for detailed cascade calculations. The kinetics of atomic cascade for $μ^- p$ and $μ^-d$ atoms is studied in the wide range of the relative target densities, $φ= 10^{-8} -1$ applying the improved version of the cascade model. It is shown that the collision-induced radiative quenching gives a significant contribution to the total disintegration of the $2s$ state of muonic atoms at energies below the $2s-2p$ threshold. The initial population of the $2s$ state for both muonic hydrogen and deuterium atoms, absolute intensities and probabilities of the different disintegration modes as well as their lifetimes are calculated for the fractions with kinetic energies above and below the $2s-2p$ threshold. The obtained results are compared with the known experimental data.

physics.atom-ph↗

arXiv2018

Line shape analysis of the K$β$ transition in muonic hydrogen

The K$β$ transition in muonic hydrogen was measured with a high-resolution crystal spectrometer. The spectrum is shown to be sensitive to the ground-state hyperfine splitting, the corresponding triplet-to-singlet ratio, and the kinetic energy distribution in the $3p$ state. The hyperfine splitting and triplet-to-singlet ratio are found to be consistent with the values expected from theoretical and experimental investigations and, therefore, were fixed accordingly in order to reduce the uncertainties in the further reconstruction of the kinetic energy distribution. The presence of high-energetic components was established and quantified in both a phenomenological, i.e. cascade-model-free fit, and in a direct deconvolution of the Doppler broadening based on the Bayesian approach.

physics.atom-ph↗

arXiv2017

Anisotropies in the linear polarization of vacancy photoluminescence in diamond induced by crystal rotations and strong magnetic fields

We study the linear polarization properties of the photoluminescence of the neutral and negatively charged nitrogen vacancies and neutral vacancies in diamond crystals as function of their symmetry and their response to strong external magnetic fields. The linear polarization degree, which exceeds 10% at room temperature, and rotation of the polarization plane of their zero-phonon lines significantly depend on the crystal rotation around specific axes demonstrating anisotropic angular evolutions. The sign of the polarization plane rotation is changed periodically through the crystal rotation, which indicates a switching between electron excited states of orthogonal linear polarizations. At external magnetic fields of up to 10 T, the angular dependences of the linear polarization degree experience a remarkable phase shift. Moreover, the rotation of the linear polarization plane increases linearly with rising magnetic field at 6 K and room temperature, for the negatively charged nitrogen vacancies, which is attributed to magneto-optical Faraday rotation.

cond-mat.mes-hall↗

arXiv2016

The isotopic effects in the scattering and the kinetics of the atomic cascade

{\it Ab initio} quantum-mechanical calculations of the differential and integrated cross sections of the elastic scattering, Stark transitions, and Coulomb de-excitation at collisions of excited $μ^- p$ and $μ^- d$ atoms with hydrogen isotope atoms in the ground state are performed. The scattering processes are treated in a unified manner in the framework of the close-coupling approach. The used basis includes both open and closed channels corresponding to all exotic atom states with principal quantum numbers from $n=1$ up to $n_{\rm max}=20$. The energy shifts of $ns$ states due to electron vacuum polarization and finite nuclear size are taken into account. The kinetics of atomic cascade of $μ^- p$ and $μ^- d$ atoms are studied in a wide range of relative target densities ($φ= 10^{-8} -1$) within the improved version of the extended cascade model. The results of the numerical quantum-mechanical calculations of the cross sections for quantum numbers and kinetic energies of muonic atoms, that are of interest for the detailed cascade calculations, are used as input data. Initial $(n,l,E)$-distributions of muonic atoms at the instant of their formation and the target motion are taken into account explicitly in present cascade calculations. The comparison of the calculated cross sections, kinetic energy distributions at the instant of the $np\to 1s$ radiative transitions as well as the absolute and relative $x$-ray yields for both muonic hydrogen and muonic deuterium reveals the isotopic effects, which, in principal, may be observed experimentally. The present results are mainly in very good agreement with experimental data available in the literature.

nucl-th↗

arXiv2008

Long-lived $2s$ state of muonic hydrogen: population and lifetime

Ab initio study of the density-dependent population and lifetime of the long-lived $(μp)_{2s}$ and the yield of $(μp)_{1s}$ atoms with kinetic energy 0.9 keV have been performed for the first time. The direct Coulomb $2s\to 1s$ deexcitation is proved to be the dominant quenching mechanism of the $2s$ state at kinetic energy below $2p$ threshold and explain the lifetime of the metastable $2s$ state and high-energy 0.9 keV component of $(μp)_{1S}$ observed at low densities. The cross sections of the elastic, Stark and Coulomb deexcitation processes have been calculated in the close-coupling approach taking into account for the first time both the closed channels and the threshold effects due to vacuum polarization shifts of the $ns$ states. The cross sections are used as the input data in the detailed study of the atomic cascade kinetics. The theoretical predictions are compared with the known experimental data at low densities. The 40% yield of the 0.9 keV$(μp)_{1s}$ atoms is predicted for liquid hydrogen density.

nucl-th↗

arXiv2007

Scattering Processes of Excited Exotic Atoms: Close-Coupling Approach

The scattering processes of exotic atoms in excited states from hydrogen such as elastic scattering, Stark transitions and Coulomb de-excitation are studied within a close coupling approach. The vacuum polarization and the strong interaction shifts of $ns$-states (in case of hadronic atoms) are taken into account. The differential and integral cross sections of the above processes are calculated to use them as the input in cascade calculations. The effect of closed channels on the scattering processes is investigated.

nucl-th↗

arXiv2007

Atomic Cascade in Muonic and Hadronic Hydrogen Atoms

The atomic cascade in $μ^- p$ and $π^- p$ atoms has been studied with the improved version of the extended cascade model in which new quantum mechanical calculations of the differential and integral cross sections of the elastic scattering, Stark transitions and Coulomb de-excitation have been included for the principal quantum number values $n\le 8$ and the relative energies $E \ge 0.01$ eV. The $X$-ray yields and kinetic energy distributions are compared with the experimental data.

nucl-th↗

arXiv2006

Scattering processes in antiprotonic hydrogen - hydrogen atom collisions

The elastic scattering, Stark transitions and Coulomb deexcitation of excited antiprotonic hydrogen atom in collisions with hydrogenic atom have been studied in the framework of the fully quantum-mechanical close-coupling method for the first time. The total cross sections $σ_{nl \to n'l'}(E)$ and averaged on the initial angular momentum $l$ cross sections $σ_{n\to n'}(E)$ have been calculated for the initial states of $(\bar{p}p)_{n}$ atoms with the principal quantum number $n=3 - 14 $ and at the relative energies $E=0.05 - 50$ eV. The energy shifts of the $ns$ states due to the strong interaction and relativistic effects are taken into account. Some of our results are compared with the semiclassical calculations.

nucl-th↗

arXiv2005

Angular distributions of scattered excited muonic hydrogen atoms

Differential cross sections of the Coulomb deexcitation in the collisions of excited muonic hydrogen with the hydrogen atom have been studied for the first time. In the framework of the fully quantum-mechanical close-coupling approach both the differential cross sections for the $nl \to n'l'$ transitions and $l$-averaged differential cross sections have been calculated for exotic atom in the initial states with the principle quantum number $n=2 - 6$ at relative motion energies $E_{\rm {cm}}=0.01 - 15$ eV and at scattering angles $θ_{\rm {cm}}=0 - 180^{\circ}$. The vacuum polarization shifts of the $ns$-states are taken into account. The calculated in the same approach differential cross sections of the elastic and Stark scattering are also presented. The main features of the calculated differential cross sections are discussed and a strong anisotropy of cross sections for the Coulomb deexcitation is predicted.

nucl-th↗

arXiv2005

Coulomb deexcitation of pionic hydrogen within close-coupling method

The Coulomb deexcitation of $(πp)$ atom in collisions with the hydrogen atom has been studied in the fully quantum mechanical close-coupling approach for the first time. The total Coulomb deexcitation cross-sections of $nl\to n'l'$ transitions and $l$-averaged cross-sections are calculated for $n=3 - 8$ and at the relative energies $E=0.01 - 100$ eV. The strong interaction and vacuum polarization shifts of $ns$-states are taken into account. It is shown that the $Δn > 1$ transitions are very important and make up a substantial fraction of the Coulomb deexcitation cross-section (up to $\sim 47%$).

nucl-th↗

arXiv2005

Non-reactive scattering of excited exotic hydrogen atoms

The Coulomb deexcitation of light exotic atoms in collisions with hydrogen atoms has been studied in the framework of the fully quantum-mechanical close-coupling method for the first time. The calculations of the $l$-averaged cross sections have been performed for $(μp)_n$ and $(μd)_n$ atoms in the states with the principal quantum number $n=3 ÷8$ and relative energies region $E=0.01 ÷100$ eV. The obtained results reveal the new $n$ and $E$ dependences of the Coulomb deexcitation cross sections. The large fraction (up to $\sim$ 36%) of the transition with $Δn > 1$ is also predicted.

nucl-th↗