Coupled-cluster calculations of properties of Boron atom as a monovalent system

We present relativistic coupled-cluster (CC) calculations of energies, magnetic-dipole hyperfine constants, and electric-dipole transition amplitudes for low-lying states of atomic boron. The trivalent boron atom is computationally treated as a monovalent system. We explore performance of the CC method at various approximations. Our most complete treatment involves singles, doubles and the leading valence triples. The calculations are done using several approximations in the coupled-cluster (CC) method. The results are within 0.2-0.4% of the energy benchmarks. The hyperfine constants are reproduced with 1-2% accuracy

Resolving all-order method convergence problems for atomic physics applications

The development of the relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Hartree-Fock wave function are included to all orders of perturbation theory led to many important results for study of fundamental symmetries, development of atomic clocks, ultracold atom physics, and others, as well as provided recommended values of many atomic properties critically evaluated for their accuracy for large number of monovalent systems. This approach requires iterative solutions of the linearized coupled-cluster equations leading to convergence issues in some cases where correlation corrections are particularly large or lead to an oscillating pattern. Moreover, these issues also lead to similar problems in the CI+all-order method for many-particle systems. In this work, we have resolved most of the known convergence problems by applying two different convergence stabilizer methods, reduced linear equation (RLE) and direct inversion of iterative subspace (DIIS). Examples are presented for B, Al, Zn$^+$, and Yb$^+$. Solving these convergence problems greatly expands the number of atomic species that can be treated with the all-order methods and is anticipated to facilitate many interesting future applications

Jovian Auroral Ion Precipitation: X‐Ray Production From Oxygen and Sulfur Precipitation

Many attempts have been made to model X‐ray emission from both bremsstrahlung and ion precipitation into Jupiter's polar caps. Electron bremsstrahlung modeling has fallen short of producing the total overall power output observed by Earth‐orbit‐based X‐ray observatories. Heavy ion precipitation was able to reproduce strong X‐ray fluxes, but the proposed incident ion energies were very high ( urn:x-wiley:jgra:media:jgra55396:jgra55396-math-00011 MeV per nucleon). Now with the Juno spacecraft at Jupiter, there have been many measurements of heavy ion populations above the polar cap with energies up to 300–400 keV per nucleon (keV/u), well below the ion energies required by earlier models. Recent work has provided a new outlook on how ion‐neutral collisions in the Jovian atmosphere are occurring, providing us with an entirely new set of impact cross sections. The model presented here simulates oxygen and sulfur precipitation, taking into account the new cross sections, every collision process, the measured ion fluxes above Jupiter's polar aurora, and synthetic X‐ray spectra. We predict X‐ray fluxes, efficiencies, and spectra for various initial ion energies considering opacity effects from two different atmospheres. We demonstrate that an in situ measured heavy ion flux above Jupiter's polar cap is capable of producing over 1 GW of X‐ray emission when some assumptions are made. Comparison of our approximated synthetic X‐ray spectrum produced from in situ particle data with a simultaneous X‐ray spectrum observed by XMM‐Newton shows good agreement for the oxygen part of the spectrum but not for the sulfur part

A comparison of numerical approaches to the solution of the time-dependent Schrödinger equation in one dimension

We present a simple, one-dimensional model of an atom exposed to a time-dependent intense, short-pulse EM field with the objective of teaching undergraduates how to apply various numerical methods to study the behavior of this system as it evolves in time using several time propagation schemes. In this model, the exact Coulomb potential is replaced by a soft-core interaction to avoid the singularity at the origin. While the model has some drawbacks, it has been shown to be a reasonable representation of what occurs in the fully three-dimensional hydrogen atom. The model can be used as a tool to train undergraduate physics majors in the art of computation and software development

Data for secondary-electron production from ion precipitation at Jupiter III: Target and projectile processes in H⁺, H, and H⁻ + H<inf>2</inf> collisions

To improve the physical completeness of the data previously calculated (Schultz et al., 2017) to enable modeling of the effects of secondary electrons produced by energetic ion precipitation at Jupiter, we extend the treatment to include inelastic processes that occur simultaneously on the projectile (O, )) and target (H). Here, processes considered in the previous work (single and double ionization, transfer ionization, double capture with subsequent autoionization, single and double stripping, single and double charge transfer, and target excitation) reflecting non-simultaneous projectile and target electron transitions, are replaced with processes that include both non-simultaneous and simultaneous electronic transitions on the target and projectile. These include, for example, single ionization, single ionization with simultaneous single projectile excitation, single ionization with double projectile excitation, single ionization with single projectile stripping, and single ionization with double projectile stripping. Using this expanded set of processes, we show, via Monte Carlo ion-transport simulation, that improved representation of the energy deposition, measured by the stopping power, is obtained as compared to accepted recommended values for intermediate energies (100–2000 keV/u) where the stopping power is largest, while maintaining the existing good agreement with these recommended values for low (10–100 keV/u) and high (2000 keV/u) energies. In addition, the ion-fraction distribution is altered by use of the improved data set. Both of these effects have implications for the energy deposition by oxygen ion precipitation in an H atmosphere. Therefore, use of this expanded data set can provide a more physically realistic secondary-electron distribution, and consequently improved atmospheric reaction network, improved description of ion contribution to atmospheric currents, and therefore improved understanding of Jovian ionosphere–atmosphere coupling

A multi-center quadrature scheme for the molecular continuum

A common way to evaluate electronic integrals for polyatomic molecules is to use Becke\u27s partitioning scheme (Becke and Chem, 1988) in conjunction with overlapping grids centered at each atomic site. The Becke scheme was designed for integrands that fall off rapidly at large distances, such as those approximating bound electronic states. When applied to states in the electronic continuum, however, Becke scheme exhibits slow convergence and it is highly redundant. Here, we present a modified version of Becke scheme that is applicable to functions of the electronic continuum, such as those involved in molecular photoionization and electron–molecule scattering, and which ensures convergence and efficiency comparable to those realized in the calculation of bound states. In this modified scheme, the atomic weights already present in Becke\u27s partition are smoothly switched off within a range of few bond lengths from their respective nuclei, and complemented by an asymptotically unitary weight. The atomic integrals are evaluated on small spherical grids, centered on each atom, with size commensurate to the support of the corresponding atomic weight. The residual integral of the interstitial and long-range region is evaluated with a central master grid. The accuracy of the method is demonstrated by evaluating integrals involving integrands containing Gaussian Type Orbitals and Yukawa potentials, on the atomic sites, as well as spherical Bessel functions centered on the master grid. These functions are representative of those encountered in realistic electron-scattering and photoionization calculations in polyatomic molecules