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Journal of Physics B: Atomic, Molecular and Optical Physics - latest papers

Latest articles for Journal of Physics B: Atomic, Molecular and Optical Physics

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  • Electron–positronium scattering and Ps− photodetachment
    We investigate the fundamental three-body Coulomb process of elastic electron–positronium (e−-Ps) scattering below the Ps(n = 2) threshold. Using the complex Kohn variational method and trial wave functions that contain highly correlated Hylleraas-type terms, we accurately compute S-, P-, and D-wave phase shifts, which may be considered as benchmark results. We explicitly investigate the effect of the mixed symmetry term in the short-range part of the D-wave trial wave function on the phase shifts and resonances. Using the complex Kohn phase shifts we compute, for e−-Ps scattering, the elastic differential, elastic integrated, momentum-transfer, and ortho-para conversion cross sections and determine the importance of the complex Kohn D-wave phase shifts on these cross sections. In addition, using the short-range part of the 1S-wave trial wave function for the bound-state of the purely leptonic ion of Ps−, and the complex Kohn 1P trial wave function for the continuum state, we determine the Ps− photodetachment cross section in the length, velocity, and acceleration forms.

  • High-fidelity multipartite entanglement creation in non-Hermitian qubits
    Non-Hermitian quantum systems showcase many distinct and intriguing features with no Hermitian counterparts. One of them is the exceptional point which marks the (parity and time) symmetry phase transition, where an enhanced spectral sensitivity arises and leads to novel quantum engineering. Here we theoretically study the multipartite entanglement properties in non-Hermitian superconducting qubits, where high-fidelity entangled states can be created under strong driving fields or strong couplings among the qubits. Under an interplay between driving fields, couplings, and non-Hermiticity, we focus on generations of GHZ states or GHZ classes in three and four qubits with all-to-all couplings, which allows a fidelity approaching unity when relatively low non-Hermitian decay rates are considered. This presents an ultimate capability of non-Hermitian qubits to host a genuine and maximal multipartite entanglement. Our results can shed light on novel quantum engineering of multipartite entanglement generations in non-Hermitian qubit systems.

  • Inelastic scattering of vortex electrons beyond the Born approximation
    We present a theoretical study of the inelastic scattering of vortex electrons by a hydrogen atom. In our study, special emphasis is placed on the effects of the Coulomb interaction between a projectile electron and a target atom. To understand these effects, we construct vortex electron wave functions both from free space and distorted solutions of the Schrödinger equation. These wave functions give rise to the first Born and distorted wave scattering amplitudes, respectively. The derived theory has been employed to investigate the transition of a hydrogen atom induced by electrons with the kinetic energies in the range from 20 to 100 eV. The results of the calculations have clearly indicated that the Coulomb interaction can significantly affect the phase pattern and probability density of a vortex electron beam as well as the squared transition amplitudes. For the latter, the most pronounced effect was found for the excitation to the sublevel and large scattering angles.

  • Three-body recombination of helium atoms at cold collision energies
    Three-body recombination (TBR) of helium atoms at cold collision energies is studied using the hyperspherical adiabatic method with different realistic interaction potentials. By considering zero angular momentum J = 0 states as well as J > 0 states, we calculate the 4He TBR rates up to about 0.1 Kelvin, and analyze the influence of modern potentials on the recombination rates. We also calculate and analyze the collision induced dissociation rates.

  • L-shell photoionisation cross sections in the S+, S2+, S3+ isonuclear sequence
    We present absolute L-shell photoionisation cross sections for the S+, S2+, S3+ ions. The cross sections were obtained using the monochromatised photon beam delivered by the SOLEIL synchrotron source coupled with an ion beam extracted from an electron cyclotron resonance source (ECRIS) in the merged dual-beam configuration. The cross sections for single, double and triple ionisation were measured and combined to generate total photoionisation cross sections. For each of the S+, S2+ and S3+ ions, the photon energy regions corresponding to the excitation and ionisation of a 2p or a 2s electron (∼175–230 eV) were investigated. The experimental results are interpreted with the help of multiconfigurational Dirac–Fock (MCDF) and Breit–Pauli R-Matrix (BPRM) or Dirac R-Matrix (DARC) theoretical calculations. The former generates photoabsorption cross sections from eigenenergies and eigenfunctions obtained by solving variationally the multiconfiguration Dirac Hamiltonian while the latter calculate cross sections for photon scattering by atoms. The cross sectional spectra feature rich resonance structures with narrow natural widths (typically 100 meV) due to excitations below and up to the thresholds. This behaviour is consistent with the large number of inner-shell states based on correlation and spin–orbit mixed configurations having three open subshells. Strong and wide (typically ∼1 eV) Rydberg series of resonances due to excitations dominate above the threshold.