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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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  • Unveiling ion-impact-induced fragmentation dynamics of atoms, molecules, and clusters using the COLTRIMS reaction microscope
    Over the past 30 years, cold target recoil ion momentum spectroscopy (COLTRIMS) has emerged as a pivotal technique for investigating atomic and molecular interactions under charged particle impacts. By enabling the coincident detection of all correlated fragments with high momentum resolution, COLTRIMS has expedited detailed investigations of atomic and molecular collision processes such as electron capture, ionization, fragmentation, and energy transfer in various few-body systems. This technique has significantly advanced our understanding of quantum correlations, wavefunction entanglement, and reaction-pathway dynamics in various atomic, molecular, and cluster targets. Further technological advances-such as reaction microscopes, which enable the simultaneous detection of both electrons and ions; high-speed position-sensitive detectors; and sophisticated data analysis methods-have broadened the range of COLTRIMS-based experiments to include more complex systems, such as biomolecules and condensed-phase targets. This review offers a comprehensive overview of the significant discoveries made possible by COLTRIMS in studies involving ion beam impacts, highlights recent technical innovations, and discusses emerging research directions in this field.

  • Electron emission from methane in collisions with protons of energy 75, 150 and 300 keV and differential cross sections
    In the present study, we report the experimentally measured double differential cross section (DDCS) of electron emission from methane (CH4) in collisions with proton beams of three different energies i.e. 75, 150 and 300 keV covering intermediate to fast collision regime, which is quite a sensitive energy range to test the theoretical models. The energy and angular distributions of the DDCS are compared with the theoretical calculation based on the continuum-distorted-wave-eikonal-initial-state (CDW-EIS) model. Two different approximations of the CDW-EIS model are implemented, such as, complete neglect of differential overlap (CNDO) and molecular orbital (MO) approach with two different internuclear distance scaling parameters. In general, the qualitative agreement with the experimental data is found to be better for the MO based model with the scaling parameter value d = 1.0, where ‘d’ is the theoretical scaling parameter related to the C–H internuclear distance. The single differential cross section (SDCS) and the total cross section (TCS) are deduced from the measured DDCS data. The TCS data shows a decreasing trend with projectile energy, which qualitatively follows the existing data which seems to be higher than the present data. The CDW-EIS (MO) with provides a better agreement with the present TCS data. The post-collision interaction process is also probed by analyzing the forward-backward asymmetry as a function of projectile velocity ( ), electron velocity ( ) and the scaled velocity ( ). The CDW-EIS (MO) model predicts a much steeper fall in the asymmetry compared to the experimental slope. This indicates the partial inability of the CDW-EIS model to predict the influence of the two-center effect correctly in the intermediate-to-fast collisions.

  • Characterizing resonances in positron-sodium scattering
    We investigate resonances in positron-sodium scattering using the R-matrix propagation method formulated in hyperspherical coordinates. The interaction between the sodium core and the valence electron is described by analytical model potentials. High partial-wave resonances are calculated for collision energies up to the Na(4f) threshold. Several resonant states of previously unclear nature are identified, and their behavior is analyzed through phase-variation studies, the associated structures in the calculated cross sections, and the characteristic patterns observed in the stability plots. We also find a new sequence of quasi-dipole states supported by the ion-dipole interaction, arising from the near degeneracy of the Na(4d) and Na(4f) states in the e+-Na system. In addition, our calculations predict a relatively broad resonance manifested in the Ps formation cross section, which may become experimentally observable with improved positron-beam energy resolution and could provide valuable information for verifying positron-atom resonance phenomena.

  • Resolving the problem of complex sound velocity in binary Bose mixtures with attractive intercomponent interactions
    In 2015 Dmitry Petrov theoretically suggested that, in a binary mixture of bosons a quantum liquid droplet may arise due to the competition between attractive intercomponent and repulsive intracomponent forces. Although this prediction has been confirmed experimentally, the model by itself suffers from a serious conceptual problem: the low—lying excitation spectrum manifests a purely imaginary phonon velocity, . In the present work, we develop a self consistent theory of two-component Bose systems with attractive interspecies interactions, which accurately takes into account pair correlations in terms of anomalous and mixed densities. We have shown that this procedure is able to resolve the problem of . Limiting ourselves with a symmetric Bose mixture at zero temperature, we have found a region of stability in which a droplet can survive.

  • Vibrations of spherical nanoparticles
    The vibrational modes of spherical monoatomic gas phase nanoparticles are calculated by quantizing the solutions of Lamb. The mode cutoff gives the two types of modes equal weights, and rounds the high frequency, both in strong contrast to Debye model spectra. The calculated spectra agree fairly well with spectra obtained by numerical diagonalization of Hessians of large disordered Lennard–Jones (LJ) clusters. The effect of a symmetry in the atomic arrangement is demonstrated with calculations for ground state LJ clusters. Our calculations allow the specification of the angular momentum carried by the vibrational motion, for which an example is calculated.