1s 2s2p Research Articles

A semi-analytic approximation for a single-particle continuum wavefunction

A moderately simple approximation to the radial wavefunction of an unbound particle which carries arbitrary angular momentum l( l + 1) and which scatters from any physical potential, including one with a Coulomb tail, is presented. The approximate wavefunction has the form of a linear combination of short- and long-range analytical functions that satisfies the correct boundary conditions at both the origin and at large distances. The coefficients of the short-range functions are determined by solving a matrix equation whose elements are highly suited to numerical quadrature, and which are hardly more difficult to evaluate for l ≫ 1 than for l = 0. The coefficients of the long-range functions are determined by both the nature of the interaction at large distances and the cusp condition on the wavefunction at the origin. This wavefunction has been tested by application to pure Coulomb scattering and to electron scattering from hydrogen within the 1s–2s–2p close coupling framework.

An Analytical Formula for 1s 2s2p 3s3p3d Energy Shifts of Finite-Size Nuclei due to Fluctuating Vacuum Fields

In quantum electrodynamics, the vacuum is not empty but has fluctuating fields which cause an orbiting lepton (electron or muon) to deviate from its quantum orbit and as a result, weaken its coupling with the nucleus, thus causing small changes in lepton energy states. Therefore, in this study, the quantum electrodynamics theory is then applied to determine qualitatively the mean square positions of an oscillating lepton by taking into account the vacuum fields and nuclear size effects. The first-order time-independent perturbation theory as an approximation method is applied to solve for the small changes in the nuclear lepton interaction caused by the two effects. The general expression that can be applied to calculate the changes in lepton energy states is deduced and then applied to calculate numerically these effects on the energy states of single-electron and single muonic atoms. The results showed the dependence of these effects on the principal quantum number n, the orbital quantum number l, the azimuthal quantum number m and the proton number Z. A more significant effect on s (l = 0) states of the large atomic nucleus and muonic atoms is observed. The obtained energy level corrections can be considered as additional energy level corrections that have to be investigated for reanalyzing the existing measured nuclear structure effects and for comparison with future spectroscopic investigations. Moreover, the new proposed formula would be suitable for calculating the energy level corrections in both muonic and electronic atoms caused by the fluctuating vacuum fields.

Photoionization of aligned excited states in neon by attosecond laser pulses

We numerically describe the ionization process induced by linearly and circularly polarized extreme ultraviolet (XUV) attosecond laser pulses on an aligned atomic target, specifically the excited state Ne*(1s 22s 22p 5[]3s[]). We compute the excited atomic state by applying the time-dependent restricted-active-space self-consistent field method to fully account for the electronic correlation. We find that correlation-assisted ionization channels can dominate channels accessible without correlation. We also observe that the rotation of the photoelectron momentum distribution by circularly polarized laser pulses compared to the case of linear polarization can be explained in terms of differences in accessible ionization channels. This study shows that it is essential to include electron correlation effects to obtain an accurate description of the photoelectron emission dynamics from aligned excited states.

Photoionization of open-shell nitrogen confined in C60

Endofullerene photoionization of open-shell N@C60 is investigated using a coupled-channel, correlated R-matrix approach with additional modifications for a finite spherical-shell fullerene potential. Particular focus is on the initial-state dependence of the photoionization cross section. Comparisons show significant differences between the 1s 22s 22p 3(4S) initial state and the metastable 2D and 2P states, as well as strong confinement oscillations.

Photoionization of the open-shell nitrogen atom confined in C60

SynopsisEndofullerene photoionization of open-shell N@C60 is investigated using a coupled-channel, correlated R-matrix approach with additional modifications for a finite spherical-shell fullerene potential. Particular focus is on the initial-state dependence of the photoionization cross section. Comparisons show significant differences between the 1s 22s 22p 3(4S) initial state and the metastable 2D and 2P states, as well as strong confinement oscillatory structure.

Absolute total cross sections for electron-impact double ionization of He(1s2s3S) and He−(1s2s2p4P)

We report on the experimental determination of absolute, total cross sections for electron-impact double ionization of helium in its metastable 1s 2s 3 S state and of the helium negative ion He− (1s 2s 2p 4 P). Cross sections are measured for impact energies ranging from threshold to 1000 eV using the animated crossed beams technique. The fast, pure beam of metastable helium required for the experiment is produced by photodetachment of fast He− ions. Results for He(1s 2s 3 S) are compared to those for He(1s 2 1 S), and exhibit similar magnitude and behaviour. The cross section for He− is large compared to other negative ions and indicates the predominance of indirect ionization channels at large impact energies.

Near- K -Edge Double and Triple Detachment of the F− Negative Ion: Observation of Direct Two-Electron Ejection by a Single Photon

Double and triple detachment of the F^{-}(1s^{2}2s^{2}2p^{6}) negative ion by a single photon have been investigated in the photon energy range 660 to 1000eV. The experimental data provide unambiguous evidence for the dominant role of direct photodouble detachment with a subsequent single-Auger process in the reaction channel leading to F^{2+} product ions. Absolute cross sections were determined for the direct removal of a (1s+2p) pair of electrons from F^{-} by the absorption of a single photon.

Transfer Excitation Processes Observed in N3+–He and O3+–He Collisions at Elab = 33 eV

We measured the relative state-selective differential cross sections (DCSs) for one-electron capture reactions using a crossed-beam apparatus. The scattering angle θlab studied in the laboratory frame ranged from −3.0 to 22° and the laboratory collision energy Elab was 33 eV. Only the transfer excitation processes, i.e., the electron capture reactions with the simultaneous excitation of the projectile, were observed. The DCSs were determined for the following reactions: N3+ (1s2 2s2 1S) + He (1s2 1S) → N2+ (1s2 2s2p2 2D) + He+ (1s 2S) + 10.3 eV, O3+ (1s2 2s2 2p 2P) + He (1s2 1S) → O2+ (1s2 2s 2p3 3P) + He+ (1s 2S) + 12.7 eV, and O3+ (1s2 2s2 2p 2P) + He (1s2 1S) → O2+ (1s2 2s 2p3 3D) + He+ (1s 2S) + 15.5 eV. In the N3+–He system, the DCSs for the reaction are zero at the center-of-mass angle θcm = 0 and show a peak at a certain angle and a shoulder at a larger angle. In the O3+–He system, the DCSs are again zero at θcm = 0. The capture process to the O2+ (1s2 2s 2p3 3P) state is mainly observed at smaller...

Atomic Data and Laser Transitions in as - Like Gallium

Fine structure calculations of the energy levels, the wavelengths, the oscillator strengths, log gf and the transition probabilities for transitions among the terms belonging to 1s2 2s2 2p6 3s2 3p6 3d104s2ns, n=5-6, 1s2 2s2 2p6 3s2 3p6 3d104s2np, n=4-6, 1s2 2s2 2p6 3s2 3p6 3d104s2nd, n=4-6 and1s2 2s2 2p6 3s2 3p6 3d104s2nf, n=4-6 configurations of As (III) have been calculated using configurations interaction Cowan atomic structure code. Our calculated values for the above mentioned quantities have been compared with the corresponding experimental data and other theoretical calculations where a satisfactory agreement is found. We also report on some unpublished values for energy levels, oscillator strengths and transition probabilities for As like gallium. These atomic data are taken as the basis for studying laser transitions between levels of As(III). Excitation rate coefficients of As like gallium are calculated using the analytical formulas of Vriens and Smeets (1980) and with considering using the collisional radiative model code CRMO of Allam (2006). A simple modification to these formulas has been included by introducing effective quantum numbers. The energy values, the radiative data and rate coefficients are then used to calculate the population densities by solving the coupled rate equations. Among these calculations positive gain coefficients are found at three selected values of electron temperature, namely 7.087 eV, 14.147 eV and 21.261 eV which are displayed as a function of the electron impact density.

Energy Levels, Oscillator Strengths, and Transition Probabilities of Ni XIX and Cu XX

Energy levels, oscillator strengths, and transition probabilities, for the 1s2 2s2 2p6, 2p53l (l = 0, 1, 2), 2p54l (l = 0, 1, 2, 3) states in Ni XIX and Cu XX are calculated using COWAN code. The Correlation and relativistic effects are considered. The calculations are compared with other results in the literature. A good agreement is found. We also report on some unpublished energy values.

High Gain Predictions for Ni-Like Ta Ions

Atomic structure data and effective collision strengths for 1s2 2s2 2p6 3s2 3p6 3d10 and 54 fine-structure levels are contained in the configurations 1s2 2s2 2p6 3s2 3p6 3d9 4l (l = s, p, d, f) for the nickel-like Ta ion. These data are used in the determination of the reduced population for the 55 fine structure levels over a wide range of electron densities (from 1021 to 1023) and at various electron plasma temperatures. The gain coefficients for those transitions with a positive population inversion factor are determined and plotted against the electron density.

Structural and collisional data for Mg III and Al IV

We present in this work energy levels, oscillator strengths, radiative decay rates and fine structure collision strengths for the Mg III and Al IV ions. The 11 configurations: (1s2) 2s22p6, 2s22p53l, 2s2p63l, 2s22p54l (l⩽n-1, where n is the principal quantum number), yielding the lowest 75 levels are used. The collisional data for these two ions are missing in the literature, especially the database CHIANTI, this is the principal motivation behind the present work. Calculations have been performed using the AUTOSTRUCTURE code. AUTOSTRUCTURE treats the scattering problem in the distorted wave approach. Fine structure collision strengths are calculated for a range of electron energies from 10Ry to 240Ry. The atomic structure data are compared to available experimental and theoretical results.

Energy Levels, Transition Probabilities, Collision Strength, and Reduced Population Calculations for High Gain Predictions in Neon-Like Krypton

We calculate the atomic structure, energy levels, oscillator strengths, transition probabilities, and collision strengths for Kr XXVII. The data refer to the 157 fine-structure levels belonging to the configurations (1s2) 2s2 2p6, 2s22p53l, 2s12p63l, 2s22p54l, 2s12p64l, 2s22p55l, and 2s12p65l, where l = s, p, d, f, and the calculations are performed using the fully relativistic atomic structure program FAC. We use the obtained data to calculate the level populations and gain coefficients employing the MATLAB R2012a computer program for solving simultaneously the coupled rate equations. Finally, we determine the 157 fine-structure population levels and gain coefficients for those transitions with a positive inversion factor and plot the electron density in wide range from 1019 to 1023.

Theoretical study of the photoionization process of Ne-like Ar, Fe, Kr and Xe ions

Photoionization (PI) cross sections of the ground state 1s2 2s2 2p6 1 S0 of Ne-like Ar8+, Fe16+, Kr26+ and Xe44+ ions are calculated by using the Dirac atomic R-matrix code based on a fully relativistic R-matrix method. To analyze the detailed resonant structure, systematical calculations based on the multiconfiguration Dirac–Fock method are performed for the dominant 2s → np resonant transitions, and the resonant energies, strengths and total natural widths are presented. The resonant structures and characteristics of the PI cross sections and resonance strengths along the Ne-like sequence are discussed with emphasis on the influence of relativistic effects. For the Ar8+ ion, good agreement is found between the present results and available theoretical calculations and experimental data.

Explicitly correlated Gaussian calculations of the 2D Rydberg states of the boron atom

Accurate non-relativistic variational calculations are performed for the seven lowest members of the (2)D Rydberg series (1s(2)2s2p(2), and 1s(2)2s(2)nd, n = 3, ..., 8) of the boron atom. The wave functions of the states are expanded in terms of all-electron explicitly correlated gaussian basis functions and the effect of the finite nuclear mass is directly included in the calculations allowing for determining the isotopic shifts of the energy levels. The gaussian basis is optimized independently for each state with the aid of the analytic energy gradient with respect to the gaussian parameters. The calculations represent the highest accuracy level currently achievable for the considered states. The computed energies are compared with the available experimental data.

Energies and E1, M1, E2, M2 transition rates for states of the 2s22p, 2s2p2, and 2p3 configurations in boron-like ions between N III and Zn XXVI

Energies, E1, M1, E2, M2 transition rates, line strengths, oscillator strengths, and lifetimes from relativistic configuration interaction calculations are reported for the states of the (1s2)2s22p, 2s2p2, and 2p3 configurations in all boron-like ions between N III and Zn XXVI. Valence, core–valence, and core–core correlation effects were accounted for through single–double multireference (SD-MR) expansions to increasing sets of active orbitals.

Fine structure collision strengths for S VII lines

Energy levels, oscillator strengths, radiative decay rates and fine structure collision strengths are presented for six times ionized sulfur S VII. The atomic data are calculated with the SUPERSTRUCTURE code, where relativistic corrections are introduced according to the Breit–Pauli approach. We include in this work the (1s2) 2s22p6, 2s22p53l, 2s2p63l, 2s22p54l (l ⩽ n − 1) configurations that yield the lowest 75 levels. The scattering problem is treated in the distorted wave approach by the code DISTORTED WAVE. This produces collision strengths in LS coupling that will be used by the code JAJOM to transform them into fine structure ones. Fine structure collision strengths for transitions from the ground and the first four excited levels are presented at six electron energies from 20 to 120 Ryd by a step of 20 Ryd. Our atomic structure data are compared with the available experimental and theoretical results.

Extreme ultraviolet and soft x-ray laser emission from Ni-like Nd ions

We use the energy levels, transition probabilities, and effective collision strengths for the states 1s2 2s2 2p6 3s2 3p6 3d10 and 1s2 2s2 2p6 3s2 3p6 3d9 4 l (l = s, p, d, and f) of a nickel-like Nd ion to determine reduced population for 55 fine-structure levels over a wide range of electron density values (from 1020 to 4 · 1022 cm−3) at various electron plasma temperatures in the range of 1–2 keV. We find the gain coefficients for those transitions with the positive population inversion factor and show their dependences on the electron density.

Search for Laser Lines in Sodium like Fe Plasmas

Energy levels, transition probabilities and effective collision strength for 1s2 2s2 2p6 3l, 4l, 5l (l = 0, 1, 2, 3, 4) states of sodium like Fe are used in the determination of the reduced populations for 21 fine structure levels over a wide rang of electron density values (1018 to 1020 cm–3) and at against electron plasma temperatures. Gain coefficients are evaluated and plotted against the electron density.

Energy Levels and Oscillator Strength of Ni XXIII

Energy levels and oscillator strengths have been calculated for the fine-structure transitions among the levels of the (1s) 2s2p, 2s2p, 2p, 2s2p3s, 2s2p3p, and 2s2p3d configurations of Ni XXIII using the graspVU and FAC program. The extensive configuration interaction and relativistic effects have been included while generating the wave functions. The results are compared with other recent theoretical estimates, and their accuracy is assessed.