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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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Optimizing frequency conversion based on three-wave mixing in a microring with pulse driving
High-quality Kerr-nonlinear optical microresonators driven by continuous-wave lasers have enabled the generation of coherent frequency conversion. Here, we take an alternative approach by using different types of pulses to drive a nonlinear microring resonator and leveraging the three-wave mixing process to generate and shape the converted pulses. The results reveal that the conversion efficiency and the shape quality of the converted pulse are collectively determined by the pump pulse profile, the external coupling rate between the resonator and waveguide, and the temporal offset between the two driving pulses. For a given pump energy, the optimized pump pulse that achieves the highest shape quality in the converted pulses does not necessarily yield the maximum conversion efficiency. Furthermore, we propose a genetic iterative algorithm to determine the optimal pump pulse shape for maximizing conversion efficiency under fixed coupling and signal light conditions. Meanwhile, this scheme, proposed to determine the optimal conditions for achieving maximum conversion efficiency, can be extended to investigate other pulse-driven nonlinear optical processes.
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Electron–molecule elastic scattering: a study using the configuration interaction method and model potentials
In this work, the theory of electron–molecule scattering and the influence of model potentials on improving differential cross-section (DCS) results are addressed. Unlike the treatment that uses the Hartree–Fock (HF) approximation, the configuration interaction method (CI) is employed to treat the target and obtain the static and exchange potentials. Using CI, the influence and behavior of the correlation-polarization model potential proposed by Padial and Norcross, as well as the potential called free parameter B, are analyzed in the calculation of DCS for elastic scattering, within the energy range of 5 eV – 20 eV. By comparing the results with experimental data and other theoretical results, it is shown that, although the Padial and Norcross potential is widely used in conjunction with HF and leads to satisfactory results in this case, its use with the CI method leads to unsatisfactory results, particularly for low scattering angles. On the other hand, the free parameter B potential appears to be more appropriate for including polarization effects, with no need for corrections related to electron correlation. The Lippmann–Schwinger equation, applied to scattering theory, is solved using the iterative variational method of Schwinger variational iterative method (SVIM), and in the CI calculation, single and double excitations are included.
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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.
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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.
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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.