Results 1 - 10 of 2909
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[en] We present high resolution photoassociation spectroscopy of ultracold 23Na133Cs molecules in a long-range c3Σ+ state below the (3S1/2 + 6P3/2) asymptote. We perform photoassociation spectroscopy in a dual-species magneto-optical trap (MOT) and detect the photoassociation resonances using trap-loss spectroscopy. By fitting the experimental data with the semi-classical LeRoy–Bernstein formula, we deduce the long-range molecular coefficient C 6 and derive the empirical potential energy curve in the long-range region. (paper)
[en] Precision studies of Raman scattering in isotopically pure 28Si, 29Si, and 30Si single crystals have been performed in the temperature range from 8 to 300 K. It was found that the quantum effects manifest themselves noticeably at low temperatures (T ≤ 100 K). This can be seen from the difference ∼(0.4 ± 0.1) cm−1 between the normalized frequencies of two extreme 28Si and 30Si isotopes, while at room temperature, quantum effects are not visible and are comparable with the measurement error of frequencies (0.1 cm−1). Raman scattering in silicon isotopes in the region of noticeable quantum effects has been studied under hydrostatic conditions at pressures to 12 GPa and at a temperature of Т = 80 K. Quantum effects are not changed under compression within the accuracy of measurements. (paper)
[en] The objective of this work was to detect the inclusion of animal meal in Japanese quail (Coturnix coturnix japonica) diets, by analyzing eggs and their fractions (albumen and yolk) through the technique of carbon (13C/12C) and nitrogen (15N/14N) stable isotopes. Four hundred and thirty-two Japanese quails, 45-day-old females, were distributed in a completely randomized experimental design, in eight treatments: T1, strictly vegetable diet (VEG), with corn (Zea mays) and soybean (Glycine max) meal; T2, bovine meat and bone meal (BM); T3, poultry viscera meal (OM); T4, feather meal (FM); T5, BM+OM; T6, BM+FM; T7, OM+FM; and T8, BM+OM+FM. Sixteen eggs were randomly collected from each treatment – eight for whole egg analysis and eight for separate yolk and albumen analyses. To determine the turnover rate, the exponential isotope dilution model was used. The application of C and N stable isotopes allows identifying the use of animal meal in coded diets through the analysis of whole eggs and their fractions, which suggests that this technique is a promising tool for the traceability and certification of products of animal origin. (author)
[en] The structural features of 10B are studied by analyzing the dissociation of nuclei of this isotope at an energy of 1 A GeV in nuclear track emulsion. The fraction of the 10B → 2He + H channel in the charge state distribution of fragments is 78%. It was determined based on the measurements of fragment emission angles that unstable 8Beg.s. nuclei appear with a probability of (26 ± 4)%, and (14 ± 3)% of them are produced in decays of an unstable 9Bg.s. nucleus. The Be + H channel was suppressed to approximately 1%.
[en] The use of the density matrix is the most direct way to work with polarization parameters. The solutions of the equation for the density matrix are obtained for hydrogen and deuterium. The magnetic moments of nuclei are explicitly incorporated into the equations, even though numerically it does not make a big difference. It is shown that in the general case the density matrix can not be reduced to the one with the only spin variables of the nucleus in contradiction with the statement of K. Blum [K. Blum, Density Matrix Theory and Applications].
[en] The Faddeev differential equations for a system of three particles with a hard-core interaction are described. Numerical results on the binding energies of the 4He3 and 3He4He2 trimers and on ultracold collisions of 3,4He atoms with 4He2 dimers obtained with the help of those differential equations are reviewed. The results obtained for the hard-core model using the Faddeev equations are compared with analogous results obtained by alternative methods.
[en] We make use of the ionisation energy theory, Ramachandran interaction theory and the energy-level spacing renormalisation group technique to extend the Drude Hamiltonian to derive the Ramachandran pairing mechanism. This particular mechanism is exploited to explain the notorious discontinuous jumps in the specific heat data at critical points in both He-4 and He-3 superfluids. The well-known spin states (due to Balian–Werthamer and Anderson–Brinkman–Morel theories) and the Leggett’s spontaneously broken spin-orbit symmetry are shown to enhance Ramachandran attraction between two He-3 atoms without the need to invoke the spin-induced pairing or the phonon-mediated Cooper pairing mechanism in superconductors. In addition, we shall show physically that the spin-exchange mechanism can neither cause pairing between electrons nor between He-3 atoms. (author)
[en] Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of d(d,p)t, d(d,n)3He and 3He(d,p)4He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN (0.01
9 <10). Their value were therefore used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances of D, 3,4He and 7Li. The obtained abundances are in agreement, within the experimental errors, with those obtained using the compilation of direct reaction rates. Moreover, a comparison of our predictions with the observations for primordial abundance of 3,4He, D and 7Li show an agreement for 3,4He and D, while showing a relevant discrepancy for 7Li
[en] Recent dynamical fusion models for weakly bound nuclei at low incident energies, based on a time-dependent perspective, are briefly presented. The main features of both the PLATYPUS model and a new quantum approach are highlighted. In contrast to existing time-dependent quantum models, the present quantum approach separates the complete and incomplete fusion from the total fusion. Calculations performed within a toy model for 6Li + 209Bi at near-barrier energies show that converged excitation functions for total, complete and incomplete fusion can be determined with the time-dependent wave-packet dynamics. (authors)
[en] The project in producing the hyperpolarized 3He and 19F are addressed in pursuit of radiation free medical diagnosis. The program for production of the hyperpolarized 3He by the brute force method with the Pomeranchuk cooling and the rapid melting of the solid 3He started a few years ago, and is still on the way, while a new program for production of the hyperpolarized 19F by means of the PHIP (ParaHydrogen Induced Polarization) has just got started. Particular attention is placed upon a new idea of the hyperpolarization catalyst to be used for 19F.