A scheme of an intense coherent gamma-ray source based on the spontaneous radiation of positronium atoms in a Bose-Einstein condensate (BEC) due to two-photon collective annihilation decay is investigated analytically arising from the second quantized formalism. It is shown that because of the intrinsic instability of annihilation decay of BEC, the spontaneously emitted entangled photon pairs are amplified, leading to an exponential buildup of a macroscopic population into end-fire modes at a certain shape of the elongated condensate. The considered scheme may also be applied to a BEC of atoms or quasiparticles as a laser mechanism with double coherence to create entangled photonic beams with a macroscopic number of photons.
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http://dx.doi.org/10.1103/PhysRevLett.113.023904 | DOI Listing |
Phys Rev Lett
December 2024
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
We have measured the spin polarization of a slow positron beam via state-selective depopulation of 2^{3}S_{1} positronium atoms, generated by passing the beam through a gas cell. Our method employs circularly polarized microwave radiation to drive 2^{3}S_{1}→2^{3}P_{1} transitions, for which either Δm_{J}=+1 or Δm_{J}=-1, and relies on the fact that asymmetries between the two cases yield the underlying positron beam polarization. Using this technique we show that the polarization of a positron beam derived from a solid neon moderator may be increased from 30% to 90% by increasing the moderator thickness, with an associated reduction in beam intensity of 60%.
View Article and Find Full Text PDFRSC Adv
December 2024
Department of Physics, Indian Institute of Technology (Indian School of Mines), Atomic and Molecular Physics Laboratory Dhanbad - 826004 Jharkhand India
This article reports an investigation of positron impact scattering from several phosphorus-bearing compounds detected in the interstellar medium. The targets studied are HCP, CCP, CP, PN, and PO. For our theoretical model, we employed the spherical complex optical potential (SCOP) and complex scattering potential - ionization contribution (CSP-ic) methods.
View Article and Find Full Text PDFSci Rep
October 2024
Physics Department, Faculty of Science, Minia University, P.O. Box 61519, Minia, Egypt.
The positron annihilation lifetime (PAL) spectroscopy characteristics of ethylene-propylene-diene monomer rubber (EPDM) composites reinforced with treated wheat husk fibers (WHFs) were investigated for the first time. PAL spectroscopy is employed to study the free volume of polymers. The use of lignocellulosic materials as reinforcement in polymeric composites has gained attention due to their low cost, availability, and eco-friendliness.
View Article and Find Full Text PDFNature
September 2024
Photon Science Centre, School of Engineering, The University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, Japan.
When laser radiation is skilfully applied, atoms and molecules can be cooled, allowing the precise measurements and control of quantum systems. This is essential for the fundamental studies of physics as well as practical applications such as precision spectroscopy, ultracold gases with quantum statistical properties and quantum computing. In laser cooling, atoms are slowed to otherwise unattainable velocities through repeated cycles of laser photon absorption and spontaneous emission in random directions.
View Article and Find Full Text PDFPhys Chem Chem Phys
July 2024
Department of Chemistry, Universidad Nacional de Colombia, Av. Cra 30 45-03, Bogotá, Colombia.
Positronium (Ps) exhibits the ability to form energetically stable complexes with atoms and molecules before annihilation occurs. In particular, F, a halogen, shows the highest reported positronium binding energy (2.95 eV) in the periodic table.
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