Newsfeeds
Journal of Physics B: Atomic, Molecular and Optical Physics - latest papers
Latest articles for Journal of Physics B: Atomic, Molecular and Optical Physics
-
Electron impact ionization cross sections and non-Maxwellian rate coefficients for Si ...
In a recent study, Pain et al 2025 (J. Phys. B: At. Mol. Opt. Phys.58 015002) reported the electron impact single ionization (EISI) cross sections for Si ions, ranging from Si3+ to Si7+. However, their distorted-wave (DW) predictions underestimated the experimental values by 15% to 57%, attributed to their consideration of only the direct ionization (DI) process while neglecting the excitation autoionization (EA), particularly for Si3+. In addition, for Si4+, contributions from the metastable state observed experimentally were not included in previous calculations. To address these limitations, we revisited the EISI cross sections of Si (where q = 3–7) employing the Level-to-Level Distorted-Wave method, considering both the DI and the EA processes. For Si4+, we account for the metastable state by adopting a weighted total cross section that comprises contributions 85% from the ground state and 15% from the metastable state. The revised results align closely with the experimental data. Furthermore, we investigate the impact of non-Maxwellian energy distributions on the rate coefficients of electron impact multiple ionization (EIMI) processes for Si . The ‘shifted’ Maxwellian distribution, kappa distribution, and superstatistics distribution are employed to evaluate the EIMI rate coefficients. We calculate the EIMI cross sections using the semi-empirical formula proposed by Bélenger et al and modified by Hahn et al. Our investigation reveals that, for these non-Maxwellian distributions, the reaction rate is significantly enhanced compared to the Maxwellian distribution, particularly at relatively low electron temperatures.
-
Reconfigurable bandpass filter based on SSPP and SIW used in radar system
In this paper, a hybrid circuit for spoof surface plasmon polaritons (SSPPs) and substrate integrated waveguide (SIW) to implement reconfigurable bandpass filter devices is reported. The hybrid circuit consists of reconfigurable corrugated metal strip and SIW. The upper cut-off frequency is controlled using SIW modulation, and the lower cut-off frequency of the filter is adjusted using capacitors. We demonstrate that ultra-broadband conversion can be achieved by tuning the geometric parameters of the SIW and the capacitance of the SSPP waveguide. Simulated and experimental results show good agreement for the fabricated hybrid circuit, exhibiting reconfigurable passbands ranging from 10 to 19.64 GHz (96.4%), out-of-band rejection up to 45 dB, and transmission loss below 2.36 dB. The proposed filter exhibits excellent performance, including a wide passband and low loss. The proposed hybrid circuit bandpass filter offers great potential for accelerating the development of integrated circuits and plasmonic devices at microwave and terahertz frequencies, while suitable for radar system applications.
-
Equilibrium and non equilibrium charge state distribution of fast Ti ...
The equilibrium and non equilibrium charge state distribution of ( = 3–7) passing through carbon foils of varying thicknesses have been measured across an energy range 0.83–2 MeV u−1. Key parameters of outgoing projectile, such as charge state fractions , mean charge state (MCS) , distribution width d, and skewness s have been determined and compared with predictions from the ETACHA4 code. Equilibration is achieved with carbon foils of 20 μg cm−2 and thicker throughout the energy range studied. The Fermi gas model (FGM) has been employed to estimate the MCS inside the target, and these values are compared with the experimental equilibrium MCSs. A notable discrepancy has been observed between experimental findings and FGM estimations, which is attributed to non radiative electron capture occurring at the target’s exit surface, influenced by wake effect and dynamic screening. Furthermore, a comparison of the experimental MCS with empirical models indicates that the Shima–Ishihara–Mikumo model provides a more accurate fit to the experimental data.
-
Generation of frequency entanglement by rotating Doppler effect
We propose a method to generate the frequency entanglement, allowing a continuous generation of entangled two-photon states in a hybrid degree of freedom by post-manipulation. Our method is based on type-II spontaneous parametric down-conversion in a nonlinear crystal and the rotation Doppler effect by rotating the q-plates, without preset discrete frequency entanglement. This allows the arbitrary modification of frequency entangled photons in a wide frequency range at room temperature, offering enhanced flexibility for quantum information tasks and quantum metrology. We also analyze the entanglement state by a combined calculation for the joint spectrum and Hong-Ou-Mandel interference of the two photons, which can be used to reconstruct a restricted density matrix in the frequency space.
-
Calculation of electronic and response properties of a hydrogen atom in soft confinement potential: a variational approach
The electronic properties of atoms confined in finite or infinite boxes with discontinuity have been extensively studied by the researchers. Recently, smooth or continuous versions of such confining potentials given by with stiffness parameter N and confinement radius R have been considered. This soft-potential coincides with the infinite discontinuous hard-wall potential as . In this paper, we study the electronic properties of a hydrogen atom confined in a soft-wall potential using a variational approach. For this purpose, we construct the variational wave functions representing the ground state as well as a few low-lying excited states. The variational wave functions yield quite accurate results for a wide range of values of R and N. We also employ the variational ground-state wave function to calculate dipole (α1) and quadrupole (α2) polarizabilities and van der Waals coefficients C6 and C8.