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A feasibility study of the time reversal violation test based on polarization of annihilation photons from the decay of ortho-Positronium with the J-PET detector
摘要： The Jagiellonian Positron Emission Tomograph (J-PET) is a novel device being developed at Jagiellonian University in Krakow, Poland based on organic scintillators. J-PET is an axially symmetric and high acceptance scanner that can be used as a multi-purpose detector system. It is well suited to pursue tests of discrete symmetries in decays of positronium in addition to medical imaging. J-PET enables the measurement of both momenta and the polarization vectors of annihilation photons. The latter is a unique feature of the J-PET detector which allows the study of time reversal symmetry violation operator which can be constructed solely from the annihilation photons momenta before and after the scattering in the detector.
关键词： Time reversal symmetry,Momenta,Polarization,Annihilation photons,J-PET detector,Discrete symmetries,Ortho-positronium
更新于2025-09-23 15:23:52
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Symmetries of modes in Ni <sub/>3</sub> V <sub/>2</sub> O <sub/>8</sub> : Polarized Raman spectroscopy and ab initio phonon calculations
摘要： Knowledge of symmetries of vibrational modes is essential for understanding structural transitions and spin‐phonon coupling in multiferroics where phonons play a vital role. Using polarized Raman spectroscopy, we have identified and assigned symmetries of 30 out of the 36 expected zone‐centred phonon mode Raman active modes in Ni3V2O8. The wavenumbers are calculated using ab initio calculations. The gerade mode wavenumbers are compared with our polarized Raman data whereas ungerade mode wavenumbers are compared with the reported infrared measurements and a good agreement was observed between the experimentally measured wavenumbers and the calculated wavenumbers. The displacements of different types of vibrations calculated and visualized using ab initio phonon calculation are presented. These assignments will be useful for visualization of Raman modes that may be sensitive to different magnetic states and to explore spin–lattice coupling across magnetic transitions.
关键词： displacements of phonon modes,gerade and ungerade modes,polarized Raman spectroscopy,symmetries of Raman active modes,ab initio calculations
更新于2025-09-23 15:23:52
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A dynamical symmetry triad in high-harmonic generation revealed by attosecond recollision control
摘要： A key element of optical spectroscopy is the link between observable selection rules and the underlying symmetries of an investigated physical system. Typically, selection rules arise from the interaction of its constituents. In light-matter interaction, emergent phenomena are particularly prominent in strongly driven states of matter, as evident in light-induced variants of superconductivity, the Hall effect, and topological insulators in the condensed phase, as well as exceptional points in molecules, Kramers–Henneberger states in gases, and time-crystals in isolated many-body systems. Such emergent states are often governed by novel symmetry properties and topologies, which may be probed by external or emitted radiation fields. Here, we report on the experimental observation of an emergent class of symmetries in the electromagnetic field emitted by a strongly driven atomic system. Specifically, we analyze the sets of allowed and forbidden harmonic orders in high-harmonic generation from tailored bi-circular and bi-elliptical fields. Corroborated by theoretical modeling, the identified selection rules correspond to a complete triad of dynamical symmetries. We believe that the general principles underlying our observations will be equally relevant for other systems, including crystalline solids.
关键词： bi-elliptical fields,optical spectroscopy,high-harmonic generation,dynamical symmetries,selection rules,bi-circular fields,symmetries
更新于2025-09-19 17:13:59
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Mini-Review: Hydrogen Atoms in a High-Frequency Laser Field
摘要： Because of the continuing advances in developing lasers in the far-ultraviolet and x-ray ranges, studies of the behavior of atoms under a high-frequency laser ?eld are of theoretical and practical interest. In the present paper, we review various analytical results obtained by the method of separating rapid and slow subsystems for various polarizations of the laser ?eld. Speci?cally, we review the corresponding analytical results both in terms of the quantum description of the phenomena involved and in terms of the classical description of the phenomena involved. We point out that, for the classical description of hydrogen atoms in a high-frequency laser ?eld, there are interesting celestial analogies. We discuss hidden symmetries of these physical systems, the advantages of this analytical method, and the connection between these results and the transition to chaos.
关键词： separation of rapid and slow subsystems,celestial analogies,atoms in a high-frequency laser ?eld,hidden symmetries
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Multi-Scale Symmetries and Selection Rules in High Harmonic Generation
摘要： Symmetry-based analysis is very useful in many fields of science. In the case of time-dependent systems, the symmetries of interest are dynamical, and are maintained during the system’s evolution in time. Interestingly, such symmetries may manifest over several length scales, e.g. both microscopically and macroscopically. For example, in high harmonic generation (HHG), micro-scale dynamical symmetries (DSs) yield selection rules that forbid some harmonic orders and determine the polarizations of the allowed harmonics [1], as was formulated recently in a consistent group theory [2]. Macroscopically, DSs of the wave equation may induce selection rules with respect to phase-matching conditions and conservation of angular or linear momentum [3]. However, the DSs of these different length scales are generally thought to be non-interacting, and have so far only been described separately. Here we formulate and explore plethora of multi-scale dynamical symmetries (MSDS), where the symmetry operations involve both microscopic and macroscopic length scales. We derive all possible MSDS operations and their resulting selection rules in HHG, and experimentally demonstrate non-trivial selection rules of the new theory.
关键词： selection rules,dynamical symmetries,high harmonic generation,multi-scale dynamical symmetries,symmetry-based analysis
更新于2025-09-11 14:15:04
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Effect of multiorbital contributions to strong-field ionization of benzene derivatives
摘要： Strong-?eld ionization of benzene, ?uorobenzene, benzonitrile, and 1-chloro-2-?uorobenzene is studied within the framework of real-space and real-time time-dependent density functional theory. Analysis of the ionization rates as a function of the molecule orientation reveals a signi?cant contribution from multiple inner Kohn-Sham orbitals that depends on the electronic structure and on the orbital symmetries of the molecule, as well as on the polarization and intensity of the external laser ?eld. Calculated photoelectron angular distributions at different molecular orientations and in response to laser ?elds with different degrees of ellipticity further demonstrate the spatial dependency of the orbital ionization rates.
关键词： orbital symmetries,time-dependent density functional theory,strong-?eld ionization,benzene derivatives,photoelectron angular distributions
更新于2025-09-10 09:29:36