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1.
The 0? states in the 156Gd nucleus at E = 1952.38 keV and in the 158Gd nucleus at E = 2269.16 keV are established on the basis of an analysis of available data on even-even deformed nuclei. From data on the deexcitation of the levels and on the probability of their population by beta transitions, it is found that these states have a two-particle proton structure. A comparison of our data with information about the 0? levels in the 170Yb and 176Hf nuclei makes it possible to conclude that Jπ0? two-particle states exist at an excitation energy of about 2 MeV and higher.  相似文献   

2.
Cross-sections, beam asymmetries, and recoil polarisations for the reactions γpK +Λ;γpK +Σ0, and γpK 0Σ+ have been measured by the SAPHIR, CLAS, and LEPS Collaborations with high statistics and good angular coverage for centre-of-mass energies between 1.6 and 2.3 GeV. The combined analysis of these data with data from π and η photoproduction reveals evidence for new baryon resonances in this energy region. A new P11 state with mass 1840 MeV and width 140 MeV was observed contributing to most of the fitted reactions. The data demand the presence of two D13 states at 1875 and, optimistically, at 2170 MeV.  相似文献   

3.

Abstract  

A series of 30 adenosine derivatives with three different substituents at the N6-position were prepared in order to evaluate their potential to inhibit the pathogenic protozoa Plasmodium falciparum and Trypanosoma brucei in vitro. The rationale for synthesis of these structures was the high probability of interactions with multiple adenosine associated targets and the assumption that N6-substitutents should increase stability against adenosine deaminases and allow the molecules to diffuse across parasite membranes. Starting from inosine, the new compounds were prepared as single isomers using a polymer-assisted acylation protocol enabling the straightforward isolation of the target compounds in pure form. Three of the compounds displayed anti-plasmodial and one anti-trypanosomal activity in the single digit micromolar concentration range.  相似文献   

4.
For the 156Gd and 170Yb nuclei, where the inversion of levels in the Kπ=1? bands is observed, the energies of rotational levels are calculated on the basis of the Coriolis interaction model for the states of two bands whose quantum numbers are Kπ=1?. New 0? levels are introduced in 170Yb, and the structure of 170Er is refined. The interaction parameters calculated for six nuclei are considered within the structure predicted by the quasiparticle-phonon model.  相似文献   

5.
The reaction of π0π+ photoproduction on free and quasi-free protons with γ-ray energies from 0.5 to 1.5 GeV has been studied. Its cross section was measured in the range θ π 0 ≥ 20°. The distributions of π0π+, π0n, and π+n invariant masses were analyzed. The experiment was performed using the Compton back-scattered γ-ray beam at the GRAAL facility (Grenoble, France), applying liquid deuterium and hydrogen targets and a large-aperture (almost 4π) detector. Particular attention was paid to analysis of systematic errors related to the neutron detection efficiency.  相似文献   

6.
An accurate calculation of the lowest negative electronic state of H 2 - (fixed nuclei) is reported using the CCSD(T) method and doubly augmented cc-pv5z basis set. Comparison has been made with the reference data by Senekowitsch et al. [Chem. Phys. Lett. 111 (1984) 211]. Owing to larger size of the basisset and inclusion of triple excitations, no vertical shift in this work is necessary to reproduce the asymptotics of H + H -. In addition, the effect of basis-set truncation is estimated, based on the complete-basis-set extrapolation method. The contribution of correlated electron-proton motion to the electron-energy curve for H2 dynamics is pointed out.Dedicated to Prof. Jií Horáek on the occasion of his 60th birthday.  相似文献   

7.
Experimental data on some long bands in N=88–98 deformed nuclei are analyzed on the basis of a method systematizing the energies of levels and inertial parameters and a method employing the analogy between neighboring. Beta bands built on low-lying 0 2 + levels are identified in N=90 isotones, including the 158Er, 160Yb, and 162Hf nuclei. Some of intermediate members of these bands have not been found yet. The systematic properties of 4? bands are presented, and the dynamics of the inertial parameters of these bands in N=88–98 isotones is revealed. The bands are identified in 158Yb, 156Dy, 156Er, 162Yb, and 166Hf.  相似文献   

8.
The ρρN and ρρΔ three-body systems have been studied within the framework of the fixed center approximation of Faddeev equation. The ρρ interaction in isospin I = 0 , spin S = 2 is strongly attractive, and so are the N ρ, ρΔ interactions. This leads to bound states of both ρρN and ρρΔ. We find peaks of the modulus squared of the scattering matrix around 2227 MeV for ρρN, and 2372 MeV for ρρΔ. Yet, the strength of the peak for the ρρN amplitude is much smaller than for ρρΔ, weakening the case for a ρρN bound state, or a dominant ρρN component. A discussion is made on how these states can be searched for in present programs looking for multimeson final states in different reactions.  相似文献   

9.
We use experimental data on e + e ? → (η′)π+π? and conservation of vector current to estimate the branching fractions of τ? decay to η(η′)π?π0ντ. The obtained values are compared to the experimental results.  相似文献   

10.
The catalogue of negative ions in superfluid helium has been extended using the example of Ar, Kr, and Xe. Such objects cannot exist in vacuum, since the polarization attraction of an electron to the inert A atom is insufficient for the formation of the bound state A. However, these objects exist in helium as stable or metastable with a very long lifetime. The effect is due to the electron localization in liquid helium. If a mixture of excited A* atoms and electrons is prepared in the gas phase above liquid helium, the reaction A* + e = A* becomes possible for all atoms of the periodic table. Such charges can be immersed into liquid helium by the electric field. In this case, the radiative decay A* = A + e allowed in vacuum can be forbidden in liquid. This leads to the formation of the new unique objects A, which can exist in liquid helium but are absent in nature. The size of such charged formations has been determined and is close the radius of a usual electron bubble in helium.  相似文献   

11.
We perform a theoretical study based on dispersion relations of the reaction γγπ 0 π 0 emphasizing the low-energy region. We discuss how the ƒ 0(980) signal emerges in γγππ within the dispersive approach and how this fixes to a large extent the phase of the isoscalar S-wave γγππ amplitude above the threshold. This allows us to make sharper predictions for the cross-section at lower energies and our results could then be used to distinguish between different ππ isoscalar S-wave parameterizations with the advent of new precise data on πππ 0 π 0. We compare our dispersive approach with an updated calculation employing the unitary chiral perturbation theory (U gC PT). We also pay special attention to the role played by the σ-resonance in γγππ and calculate its coupling and width to γγ, for which we obtain Γ(σγγ) = (1.68 ± 0.15) keV.  相似文献   

12.
The specific heat of the ZrB12 compound in the normal and superconducting states (T C ≈ 6 K) has been studied in the 1.9–7 K temperature range for high-quality single crystals with different relative contents of boron isotopes. For Zr10B12, ZrnatB12, and Zr11B12 dodecaborides, the electron density of states and the electronphonon coupling constant, λe-ph ∼ 0.4, are found. The dependence of the thermodynamic and upper critical fields, as well as of the Ginzburg-Landau parameter (κ = 0.8–1.14) on temperature and isotope composition is determined. The results suggest the existence of the magnetic field induced phase transition at T* = 4–5 K, which is not related to the transition from type-I to type-II superconductivity. The possibilities of the existence of two-gap superconductivity and a structural phase transition at T* in zirconium dodecaboride are discussed.  相似文献   

13.
The effect of the 16O ? 18O substitution in the coordination sphere of permanganate anion MnO 4 ? on the chemical shift of 55Mn nuclei have been studied by 17O and 55Mn NMR. Time constants τ n,k of oxygen exchange in the water–permanganate anion system have been estimated. In nearly neutral solutions (pH ≈ 6.8–7.2), the oxygen exchange time is on the order of tens of hours. Bubbling gaseous HCl through this solution for a few seconds leads to the equilibrium distribution of oxygen isotopes in the manganese coordination sphere. The observed temperature dependences of isotope-induced 55Mn NMR shifts in Mn16 O 44-n 18 O n (n = 0–4) have been treated as a result of rovibrational averaging of Mn–O bond lengths. The change in the Mn—O bond length in caused by the 16O → 18O isotope substitution is on the order of 10–4 Å.  相似文献   

14.
Absolute photoionization cross sections for Ne atoms in the excited levels (Paschen notation ) were calculated at near threshold energies within the configuration interaction Pauli-Fock approach including core polarization. The computed spectra and the lineshape parameters of the odd parity 2p1/2 5ns/d autoionizing resonances are found to be in good agreement with high resolution laser spectroscopic results. Guided by the theoretical results, improved analyses of the measured spectra by superimposed Fano-type profiles were achieved. Theoretical predictions are presented for resonances which have not yet been studied experimentally. In addition, we report the absolute partial photoionization cross sections for the 2P3/2 and 2P1/2 channel at photoelectron energies up to 7 eV. Except for the highest lying 2p1(1S0) level, these cross sections monotonically decrease with energy (as reported earlier in single-electron calculations for the Ne(2p53p) configuration) with branching ratios which essentially reflect the core composition of the 2px levels. For the 2p1 level the resonance structure and the partial cross sections are strongly influenced by a Cooper-Seaton minimum in the d3/2 channel,located just above the 2P1/2 ionization limit.  相似文献   

15.
The processes of electron-positron annihilation into π0γ and into π′(1300)γ are considered within an extended NJL model. The intermediate vector mesons ρ 0, ω ρ′(1450), and ω(1420) are taken into account. The latter two mesons are treated as the first radial excited states. They are incorporated into the NJL model by means of a polynomial form factor. Numerical predictions for the cross-sections of these processes are received for the center-of-mass energies below 2 GeV. Our results for the π0γ production are in agreement with experimental data obtained in the energy region 600–1020 MeV.  相似文献   

16.
Combining the Okubo-Zweig-Iizuka rule in the decay φ→ρπ→π+π?π0 with the ρ→4π decay amplitudes, we calculate the φ→2π+?π0 and φ→π+π?0 ones. The partial widths of the above φ decays are evaluated, and the excitation curves in e+e? annihilation are obtained, assuming reasonable particular relations among the parameters characterizing the anomalous terms of the HLS Lagrangian. The evaluated branching ratios Bφ→π+π?0 ≈ 2 × 10?7 and Bφ→2π+?π0 ≈ 7 × 10?7 are such that, with the luminosity L=500 pb?1 attained at DAΦNE φ factory, one may already possess about 1685 events of the decays φ→5π.  相似文献   

17.
18.
Using 160GeV muon scattering data collected with the COMPASS experiment at CERN, the exclusive production of ωπ0 via virtual photons was studied. Selective population of a peak around 1250MeV is observed. Possible contributions from spin-parity 1- are searched for, inspecting decay angular correlations. In particular, the orientation of the ω decay plane may allow a distinction from the 1+ b 1(1235) state. Our observation is compared with indications of a (1250) in annihilation and in γp . Original article based on material presented at HADRON 2007.  相似文献   

19.
The ground-state energies and the squared moduli of the ground-state wave functions are calculated for the 3H, 3,4,6He, 6Li, and 9Be nuclei by Feynman’s continual (path) integrals method. The results are in satisfactory agreement with experimental data.  相似文献   

20.
The results of the experimental measurement and numerical simulation of the cross sections for residual radioactive nuclei production in thin 209Bi, natPb, 206Pb, 207Pb, and 208Pb targets bombarded with protons in the energy range from 0.04 to 2.6 GeV are reported. The nuclide production cross sections were measured using γ spectrometry with a high-resolution Ge detector. The experimental data include a total of 5972 reaction cross sections at 11 proton energy values. The results are compared to the data from other laboratories reported in 80 papers. The model calculations were carried out using eight simulation code packages: LAHET, INCL4 + ABLA, CEM03, LAQGSM + GEM2, CASCADE, CASCADE-2004, CASCADO, and LAHETO. A detailed analysis of discrepancies between the measured and calculated data is presented.  相似文献   

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