The azimuthal ( Formula omitted) correlation distributions between heavy-flavor decay electrons and associated charged particles are measured in pp and p-Pb collisions at Formula omitted TeV. Results ...are reported for electrons with transverse momentum Formula omitted Formula omitted and pseudorapidity Formula omitted. The associated charged particles are selected with transverse momentum Formula omitted Formula omitted, and relative pseudorapidity separation with the leading electron Formula omitted. The correlation measurements are performed to study and characterize the fragmentation and hadronization of heavy quarks. The correlation structures are fitted with a constant and two von Mises functions to obtain the baseline and the near- and away-side peaks, respectively. The results from p-Pb collisions are compared with those from pp collisions to study the effects of cold nuclear matter. In the measured trigger electron and associated particle kinematic regions, the two collision systems give consistent results. The Formula omitted distribution and the peak observables in pp and p-Pb collisions are compared with calculations from various Monte Carlo event generators.
ZnPSe
was identified as a two-dimensional material wherein valley and spin can be optically controlled in technologically relevant timescales. We report an optical characterization of ZnPSe
crystals ...that show indirect band-gap characteristics in combination with unusually strong photoluminescence. We found evidence of interband recombination from photoexcited electron-hole states with lifetimes in a microsecond timescale. Through a comparative analysis of photoluminescence and photoluminescence excitation spectra, we reconstructed the electronic band scheme relevant to fundamental processes of light absorption, carrier relaxation, and radiative recombination through interband pathways and annihilation of defect-bound excitons. The investigation of the radiative processes in the presence of a magnetic field revealed spin splitting of electronic states contributing to the ground excitonic states. Consequently, the magnetic field induces an imbalance in the number of excitons with the opposite angular momentum according to the thermal equilibrium as seen in the photoluminescence decay profiles resolved by circular polarization.
Charge neutrality and their expected itinerant nature makes excitons potential transmitters of information. However, exciton mobility remains inaccessible to traditional optical experiments that only ...create and detect excitons with negligible momentum. Here, using angle-resolved photoemission spectroscopy, we detect dispersing excitons in the quasi-one-dimensional metallic trichalcogenide, TaSe
. The low density of conduction electrons and the low dimensionality in TaSe
combined with a polaronic renormalization of the conduction band and the poorly screened interaction between these polarons and photo-induced valence holes leads to various excitonic bound states that we interpret as intrachain and interchain excitons, and possibly trions. The thresholds for the formation of a photo-hole together with an exciton appear as side valence bands with dispersions nearly parallel to the main valence band, but shifted to lower excitation energies. The energy separation between side and main valence bands can be controlled by surface doping, enabling the tuning of certain exciton properties.
The noncovalent interactions of (5,10,15,20-tetra(4-methylphenyl)porphinato)cobalt(II) (CoTTP) with Csub.60 and 1-N-methyl-2-(pyridin-4-yl)-3,4-fullero60pyrrolidine (PyCsub.60) were studied in ...toluene using absorption and fluorescence titration methods. The self-assembly in the 2:1 complexes (the triads) (Csub.60)sub.2CoTTP and (PyCsub.60)sub.2CoTTP was established. The bonding constants for (Csub.60)sub.2CoTTP and (PyCsub.60)sub.2CoTTP are defined to be (3.47 ± 0.69) × 10sup.9 and (1.47 ± 0.28) × 10sup.10 Msup.−2, respectively. sup.1H NMR, IR spectroscopy, thermogravimetric analysis and cyclic voltammetry data have provided very good support in favor of efficient complex formation in the ground state between fullerenes and CoTTP. PyCsub.60/Csub.60 fluorescence quenching in the PyCsub.60/Csub.60-CoTTP systems was studied and the fluorescence lifetime with various CoTTP additions was determined. The singlet oxygen quantum yield was determined for PyCsub.60 and the intensity decrease in the sup.1Osub.2 phosphorescence for Csub.60 and PyCsub.60 with the CoTTP addition leading to the low efficiency of intercombination conversion for the formation of the sup.3Csub.60* triplet excited state was found. Using femtosecond transient absorption measurements in toluene, the photoinduced electron transfer from the CoTTP in the excited singlet state to fullerene moiety was established. Quantum chemical calculations were used for the determination of molecular structure, stability and the HOMO/LUMO energy levels of the triads as well as to predict the localization of frontier orbitals in the triads.
The Bureau International des Poids et Mesures (BIPM) is developing, with the support of national metrology institutes, an extension to the existing international reference system for international ...comparisons in radionuclide metrology. The extended system is addressing pure alpha-, pure beta-emitting and some electron capture-decaying radionuclides. The new system is based on a custom-built liquid scintillation counter and the triple-to-double coincidence ratio (TDCR) technique. Particular emphasis was placed on long-term stability and excellent reproducibility in sample preparation. The analytical method is based on a special approach that uses the TDCR value as a parameter to compensate for fluctuations caused by changes in detection efficiency or photomultiplier asymmetries that cannot be excluded when considering very long periods. Measures for quality assurance were established. They are based on periodic controls of unquenched toluene-based liquid scintillation sources with .sup.3H and .sup.14C. In this way, the reproducibility of the system results is demonstrated for a test period of about twenty months.
The paper presents result of ab initio methods exploiting to calculate the molar extinction spectrum of some model clusters, the molecular hybrid C.sub.24H.sub.30 included. Based on the comparison of ...the calculation with the experimental spectra of the main allotropic modifications of carbon, the absorption maximum with an energy of ~6 eV in the absorption spectrum of highly tetrahedral amorphous carbon (ta-C) attributed to the pi right arrow pi* optical transitions of electrons in a single aromatic ring. The edge sites of the ring covalently bonded with the sp.sup.3-hybridised carbon atoms of the amorphous matrix. The manifestation of a shoulder in the spectrum of the imaginary part of the refractive index of a film of highly tetrahedral amorphous carbon (ta-C), 4.6 eV, is assigned to pi right arrow pi* optical transitions of clusters distorted with hybrid Stone-Wallace-like defect, also covalently bonded with the amorphous matrix.
Ionospheric F2 region peak densities (NmF2) are expected to have a positive correlation with total electron content (TEC), and electron densities usually show an anticorrelation with electron ...temperatures near the ionospheric F2 peak. However, during the 17 March 2015 great storm, the observed TEC, NmF2, and electron temperatures of the storm‐enhanced density (SED) over Millstone Hill (42.6°N, 71.5°W, 72° dip angle) show a quiet different picture. Compared with the quiet time ionosphere, TEC, the F2 region electron density peak height (hmF2), and electron temperatures above ~220 km increased, but NmF2 decreased significantly within the SED. This SED occurred where there was a negative ionospheric storm effect near the F2 peak and below it, but a positive storm effect in the topside ionosphere. Thus, this SED event was a SED in TEC but not in NmF2. The very low ionospheric densities below the F2 peak resulted in a much reduced downward heat conduction for the electrons, trapping the heat in the topside in the presence of heat source above. This, in turn, increased the topside scale height so that even though electron densities at the F2 peak were depleted, TEC increased in the SED. The depletion in NmF2 was probably caused by an increase in the density of the molecular neutrals, resulting in enhanced recombination. In addition, the storm time topside ionospheric electron density profiles were much closer to diffusive equilibrium than the nonstorm time profiles, indicating less daytime plasma flow between the ionosphere and the plasmasphere.
Key Points
A SED in TEC but not in NmF2
Storm time topside ionospheric electron density profiles were in diffusive equilibrium
Increase in the topside but decrease in bottom side ionosphere
Prospects are discussed for the studies of stimulated de-excitation of a nuclear isomer (SDNI) of the .sup.186m1Re nucleus in a plasma with electron temperature theta.sub.e on the order of the energy ...DELTAÐ of the trigger transition that excites the isomer nucleus to a higher level from which rapid decay to the ground state of the nucleus is possible. The stimulated de-excitation of the .sup.186m1Re isomer was found recently in a laser plasma with the temperature theta.sub.e ~ 1 keV and a lifetime of about 0.3 ns. However, the probability P.sub.SDNI of the stimulated de-excitation of the isomer was very small, on the order of 10.sup.-5%. To enhance P.sub.SDNI, it is proposed in this study to use instead of the laser plasma the plasma of a high-current electric discharge with a temperature of theta.sub.e ~ 1 keV, in particular, the plasma of the electrical explosion of conductors the lifetime of which may be two orders of magnitude larger than that of the laser plasma. To enable selection of the most efficient regime of the stimulation of de-excitation of nuclear isomers, a simple formula is derived that relates the estimated probability P.sub.SDNI to the plasma parameters. To enhance P.sub.SDNI, it is also proposed to additionally irradiate the plasma with photons whose frequency is in resonance with the trigger transition. A mode of multiple recurring high-current electric discharges in the plasma that contains isomer nuclei is suggested. It is noted that the available experimental and theoretical results enable already now launching development of a power source based on the .sup.186m1Re isomer.
The spectra of energy losses of reflected electrons, which are recorded with the energy of primary electrons in the range of 200-3000 eV, are investigated. From these experimental spectra, the ...spectra of the cross section of inelastic electron scattering are calculated for each energy of primary electrons as the dependence of the product of the average inelastic path length and the differential cross section of inelastic scattering of electrons on the energy losses of electrons. The fine structure of the energy losses of reflected electrons is analyzed decomposing the spectra of the cross section of inelastic scattering of electrons in the region of energy losses of valence electrons into elementary peaks. A relationship has been established for each of the elementary peaks with single and multiple energy losses due to the excitation of bulk and surface plasmons and interband transitions of electrons from the valence band to free states above the Fermi level. The obtained results are analyzed on the basis of the experimental and theoretical published data on the band structure of gamma-Fe.sub.2O.sub.3.
The recently developed ab initio many-body theory of positron molecule binding 22J. Hofierka et al., Many-body theory of positron binding to polyatomic molecules, Nature (London) 606, 688 ...(2022)NATUAS0028-083610.1038/s41586-022-04703-3 is combined with the shifted pseudostates method A. R. Swann and G. F. Gribakin, Model-potential calculations of positron binding, scattering, and annihilation for atoms and small molecules using a Gaussian basis, Phys. Rev. A 101, 022702 (2020)PLRAAN2469-992610.1103/PhysRevA.101.022702 to calculate positron scattering and annihilation rates on small molecules, namely H_{2}, N_{2}, and CH_{4}. The important effects of positron-molecule correlations are delineated. The method provides uniformly good results for annihilation rates on all the targets, from the simplest (H_{2}, for which only a sole previous calculation agrees with experiment), to larger targets, where high-quality calculations have not been available.
![Localized [pi]-Electron Sta...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1063-7826/small "Localized [pi]-Electron States in the Optical Absorption Spectrum of Tetrahedrally Coordinated Amorphous Carbon")
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