Contribution of the <Emphasis Type="Italic">M</Emphasis>1 process to the astrophysical <Emphasis Type="Italic">S</Emphasis>-factor of the <Emphasis Type="Italic">p</Emphasis><Superscript>2</Superscript>H radiative capture

The experimental data on the astrophysical S-factor of the p ²H radiative capture are well described for energies from 1 keV to 10 MeV using the potential cluster model and the Young schemes of orbital cluster state classification with allowance for the E1 and M1 transitions.     

The <Emphasis Type="Italic">B</Emphasis>(<Emphasis Type="Italic">E</Emphasis>1) strength of <Superscript>11</Superscript>Be extracted from the Coulomb excitation measurements

We have extracted the B(E1) strength for the transition 1/2⁺ → 1/2⁻ occurring in ¹¹Be from the recent Coulomb excitation measurements using the nonrelativistic and intermediate-energy Coulomb-excitation (IECE) theory and have found that the results of IECE theory are in good agreement with the adopted value of B(E1). When the survival probability of the projectile is taken into account the agreement between the calculated and the adopted value of B(E1) strength improves further. We have also studied the effect of diffuseness parameter of survival probability on the B(E1) strength. The text was submitted by the authors in English.     

Partial-wave analysis for elastic <Emphasis Type="Italic">p</Emphasis><Superscript>13</Superscript>C scattering at astrophysical energies

A standard partial-wave analysis was performed on the basis of known measurements of differential cross sections for elastic p ¹³C scattering at energies in the range 250–750 keV. This analysis revealed that, in the energy range being considered, it is sufficient to take into account the ³ S ₁ wave alone. A potential for the triplet ³ S ₁-wave state of the p ¹³C system in the region of the J ^p T = 1⁻¹ resonance at 0.55 MeV was constructed on the basis of the phase shifts obtained from the aforementioned partial-wave analysis.     

Spectroscopic investigation of thallium 6<Emphasis Type="Italic">s</Emphasis>6<Emphasis Type="Italic">p</Emphasis><Superscript>2</Superscript> configuration at electron-atom collisions: I. Spectra

Thallium emission spectra in the 115–300 nm range excited by electron-atom collisions at electron energies of 12–300 eV are investigated. A number of weak lines that cannot be unidentified using spectroscopic tables are found in the 140–170 nm range. Two of them (144.9 and 148.0 nm) are attributed to the radiative decay of levels that belong to the 6s6p ² configuration and that lie above the ionization potential. A weak emission with an excitation threshold of about 9 eV is revealed in the vicinity of the Tl II resonance line at 132.2 nm. The excitation function of the emission is measured for electron energies below 15.5 eV. It is found that the emission consists of two lines, which also appear due to the excitation of the 6s6p ² configuration and correspond to the radiative decay of levels that are common with the lines at 144.9 and 148.0 nm mentioned above. Their calculated wavelengths are 130.2 and 132.7 nm, respectively.     

Hyperfine structure of <Emphasis Type="Italic">S</Emphasis>- and <Emphasis Type="Italic">P</Emphasis>-wave states in muonic-helium ion

Corrections of order α ⁵ and α ⁶ to the hyperfine structure of S- and P-wave energy levels of the muonic-helium ion are calculated. Electron-vacuum-polarization effects, corrections for the nuclear structure, and recoil effects are taken into account. The numerical values obtained for respective hyperfine splitting, −1334.73 meV (1S), −166.64 meV (2S), −58 712.90 μeV (2P _1/2), and −24 290.69 μeV (2P _3/2), can be viewed as a reliable estimate for a comparison with experimental data, and the hyperfine-structure interval of Δ₁₂ = 8ΔE ^hfs(2S) − ΔE ^hfs(1S) = 1.59 meV can be used to test QED predictions.     

Discussion of isomeric ratios in (<Emphasis Type="Italic">p,n</Emphasis>) and (<Emphasis Type="Italic">d</Emphasis>, 2<Emphasis Type="Italic">n</Emphasis>) reaction

Isomeric ratios (IR) in the (p, n) and (d, 2n) reactions are considered. The dependence of IR values on the projectile type and energy, the target- and product-nucleus spin, the spin difference between the isomeric and ground states of products, and the product mass number is discussed. The isomeric ratios for 46 product nuclei (from ^44m,gSc to ^127m,gXe) obtained in reactions where target and product nuclei have identical mass numbers were calculated at energies from the reaction threshold to 50 MeV (with a step of ΔE = 1 MeV). The calculations in question were performed with the aid of the TALYS 1.4 code package. The calculated IR values were compared with their experimental counterparts available from the literature (EXFOR database). In the majority of cases, the calculated IR values agree well with the experimental data in question. It is noteworthy that the IR values obtained in (d, 2n) reactions are substantially greater than those in (p, n) reactions.     

Estimation of the deformation-potential constant for <Emphasis Type="Italic">p</Emphasis>-type isotropic polycrystalline silicon through the deformation potential of a <Emphasis Type="Italic">p</Emphasis>-type silicon single crystal

A method of calculating the effective deformation-potential constant E ₁ for holes and longitudinal acoustic phonons in isotropic polycrystalline silicon is suggested. The deformation-potential constant E ₁ is estimated through the deformation potentials a, b, and d of the silicon single crystal. The procedure of averaging of the squared modulus of the hole and acoustic phonon interaction Hamiltonian written in the plane wave basis over the polycrystal ensemble provides the basis for calculation of the constant E ₁ . It is demonstrated that for T = 200–600 K, hole concentration p = (5.0–10.0)∙10¹⁹ cm^–3, and crystallite size d = 300–3000 ?, the deformationpotential constant E ₁ is independent of the hole concentration p, temperature T, and crystallite size d.     

On evidence for exotic dibaryon <Emphasis Type="Italic">d</Emphasis><Subscript>1</Subscript>* (1956) in selected two-nucleon-two-photon reactions

The narrow NN-decoupled dibaryon resonance with a mass about 1956 MeV was reported in 2000 by DIB2γ Collaboration (JINR, Dubna) on the basis of the measurement of the two-photon energy spectrum in the reaction pp → pp2γ at 216 MeV. The most probable quantum numbers J ^P = 1⁺ prevent the resonance from decaying into two protons due to the exclusion principle, while the pionic decays are impossible energetically. The significance of this resonance (called d ₁* (1956)) for the interpretation of a few other exclusive and inclusive reactions connected with the photon(s) production in nucleon collisions with nucleons and nuclei at different energies is discussed. The importance is stressed of on-going and planned studies of the elastic and inelastic Compton scattering on the lightest nuclei for collecting information on the structure and dynamics of d ₁* (1956) which can shed light on its nature.     

Manifestly-covariant <Emphasis Type="Italic">p</Emphasis><Superscript>3</Superscript> calculation of nucleon Compton scattering

We compute the Compton scattering off the nucleons in the framework of manifestly covariant baryon chiral perturbation theory (BχPT). The results for observables differ substantially from the corresponding calculations in heavy-baryon chiral perturbation theory (HBχPT), most appreciably in the forward kinematics. We verify that the covariant p ³ result fulfills the forward-Compton-scattering sum rules. We also explore the effect of the Δ(1232) resonance at order p ⁴/Δ, with Δ ≈ 300 MeV, the resonance excitation energy. We find that the substantial effect of the Δ-excitation on the nucleon polarizabilities can naturally be accommodated in the manifestly covariant calculation. The article is published in the original.     

Low-lying magnetic and electric dipole strength distribution in the <Superscript>176</Superscript>Hf nucleus

In this study the QRPA approach with the rotational and translational invariant Hamiltonians has been carried out to describe magnetic and electric dipole excitations in ¹⁷⁶Hf . Calculations show that the ¹⁷⁶Hf nucleus demonstrates a very rich B(M1) strength structure and in some aspects nicely confirm the experimental data. It has been shown that the main part of spin-1 states, observed at 2-4MeV in ¹⁷⁶Hf , may be attributed to have a M1 character and may be interpreted as the main fragments of the scissors mode. The agreement between the calculated mean excitation energies as well as the summed B(M1) values of the scissors mode excitations and the available experimental data is quite good. The constructive interference between the orbit and the spin part of M1 strength has been found to be below 3.5MeV. The calculations indicate the presence of a few prominent negative-parity states in the 2-4MeV energy interval. This suggests that the supposition of the experiment “all stronger K = 1 low-lying dipole excitations were of magnetic character” cannot be generalized.     

Astrophysical <Emphasis Type="Italic">S</Emphasis> factors for radiative proton capture by <Superscript>3</Superscript>H and <Superscript>7</Superscript>Li nuclei

Within the potential cluster model where orbital states are classified according to Young diagrams and isospin, astrophysical S factors are considered for radiative proton capture by ³H and ⁷Li nuclei at energies of up to 1 and 10 keV, respectively. It is shown that the approach used, which takes into account only the E1 transition for the p ³H capture process, makes it possible to describe well the most recent experimental data at c.m. energies in the range from 50 keV to 5MeV. In the case of proton capture by ⁷Li nuclei, an M1 processwas taken into account in addition to the E1 transition, and a general behavior and the magnitude of the experimental S factor could be correctly reproduced owing to this at astrophysical energies, including the region around the resonance at 0.441 MeV (in the laboratory frame).     

Effects of <Emphasis Type="Italic">C</Emphasis>-, <Emphasis Type="Italic">P</Emphasis>-, <Emphasis Type="Italic">T</Emphasis>-symmetries violation in the polarized elastic electron-proton electroweak scattering

Analytical expressions are obtained for the angular distributions and spin asymmetries of the processes of elastic electromagnetic and electroweak scattering of high energy electrons on polarized/unpolarized proton target with account of C-, P- and T/CP-invariance violating anapole and electric dipole moments, as well as neutral weak electric, magnetic and axial form factors of the proton. Behavior of the P- and T- odd spin asymmetries is studied in dependence of the electron’s energy and scattering angle and proton form factors parameters.     

Isospin symmetry and giant resonance in nuclei of mass number <Emphasis Type="Italic">A</Emphasis> = 14

An analysis of the cross sections for photon absorption by isobar nuclei ¹⁴C and ¹⁴N in the giant-dipole-resonance region demonstrates a high degree of isospin symmetry for this type of collective excitations in the above nuclei. Giant resonances in A = 14 isobar nuclei are related by a simple rescaling procedure that is based on the fact that, for these nuclei, the isospin remains a good quantum number in the process of dipole excitations of energy up to about 40 MeV. The features of the isospin splitting of the giant resonance in the ¹⁴C nucleus are refined. The shape of the cross section for photoabsorption in the ¹⁴C nucleus—in particular, a large width of the giant resonance in this nucleus—is exhaustively explained.     

Study of thermally excited nuclei through <Emphasis Type="Italic">E</Emphasis>1 and <Emphasis Type="Italic">E</Emphasis>2 decay from collective modes

The nuclear system at the limit of excitation energy and angular momentum is here studied in the case of the superdeformed nucleus ¹⁴³Eu using -spectroscopy techniques. The data are based on a EUROBALL experiment using the reaction ³⁷Cl + ¹¹⁰Pd Eu + 4n. The influence of thermal energy on superdeformed configurations is investigated through the analysis of the quasi-continuum spectra formed by E2 transitions among states of excited rotational bands with energy extending up to 4-5 MeV above the yrast line. In particular, the effective lifetimes of the discrete rotational bands forming ridge structures in - coincidence matrices is measured by a Doppler Shift Attenuation Method. The deduced quadrupole deformation of 10 eb indicates that the nucleus maintains its collectivity with increasing excitation energy, supporting the superdeformed character of the excited nuclear rotation. The obtained number of superdeformed discrete bands forming the ridge structures is found in good agreement with microscopic cranked shell model calculations including the decay-out process into the lower deformation minimum. In addition, the nuclear properties at higher excitation energies are investigated through the E1 -decay of the giant dipole resonance (GDR). It is found that the intensity of the superdeformed yrast and excited bands increases by a factor of approximately 1.6 when a coincidence with a high-energy -ray is required, showing the importance of the E1 cooling in the feeding mechanism of the superdeformed states.Received: 2 December 2002, Published online: 2 March 2004PACS: 21.10.Tg Lifetimes - 21.10.Re Collective levels - 23.20.Lv transitions and level energies - 27.60. + j      

Re-appraisal of the <Emphasis Type="Italic">P,T</Emphasis>-odd interaction constant <Emphasis Type="Italic">W</Emphasis><Subscript>d</Subscript> in YbF: Relativistic configuration interaction approach

Restricted active space (RAS) configuration interaction (CI) approach is employed to compute the P,T-odd interaction constant W _d for the ground (²Σ_1/2) state of YbF molecule. The present estimate of W _d = −1.164 × 10²⁵ Hz/e-cm is expected to provide a reliable limit on the electron’s electric dipole moment (EDM), d _e.     

Dielectron widths of the <Emphasis Type="Italic">S</Emphasis>-, <Emphasis Type="Italic">D</Emphasis>-vector bottomonium states

The dielectron widths of Y(nS)(n = 1, …, 7) and vector decay constants are calculated using the relativistic string Hamiltonian with a universal interaction. For Y(nS) (n = 1, 2, 3) the dielectron widths and their ratios are obtained in full agreement with the latest CLEO data. For Y(10580) and Y(11020) a good agreement with experiment is reached only if the 4S-3D mixing (with a mixing angle θ = 27°± 4°) and 6S-5D mixing (with θ = 40°±5°) are taken into account. The possibility to observe higher “mixed D-wave” resonances, $ \tilde \Upsilon $ \tilde \Upsilon (n ³ D ₁) with n = 3, 4, 5 is discussed. In particular, $ \tilde \Upsilon $ \tilde \Upsilon (≈11120), originating from the pure 5³ D ₁ state, can acquire a rather large dielectron width, ∼130 eV, so that this resonance may become manifest in the e ⁺ e ⁻ experiments. On the contrary, the widths of pure D-wave states are very small, Γ _ee (n ³ D ₁)≤ 2 eV.     

Fragmentation of sputtered Si<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>O<Stack><Subscript><Emphasis Type="Italic">m</Emphasis></Subscript><Superscript>+</Superscript></Stack> clusters: Release kinetic and dissociation energies

The spectra of kinetic energies of positive Si _n O _m ⁺ cluster ions (n = 2–5, m = 2–7) have been measured using a double focusing ion microanalyzer with reverse geometry at instants 10⁻⁵ to 10⁻⁴ s after emission. The dissociation energies have been determined within the evaporative ensemble model and the theory of unimolecular decay reactions. The results obtained are compared with the binding energies of neutral Si _n O _m clusters.     

The low-energy dipole structure of <Superscript>232</Superscript>Th , <Superscript>236</Superscript>U and <Superscript>238</Superscript>U actinide nuclei

In this study, I^p = 1⁺\ensuremath I^{\pi} = 1^{+} and I^p = 1^-\ensuremath I^{\pi} = 1^{-} dipole mode excitations are systematically investigated within the rotational and translational + Galilean invariant quasiparticle random-phase approximation for ²³²Th , ²³⁶U , and ²³⁸U actinide nuclei. It is shown that the investigated nuclei reach a B(M1) strength structure, which corresponds to the scissors mode. The calculated mean excitation energies as well as the summed B(M1) value of the scissors mode excitations are consistent with the available experimental data. The results of calculations indicate large differences to the rare-earth nuclei as is the case for the experiment: a doubling of the observed dipole strengths and a shift of the energy centroid to the lower energies by about 800keV. The calculations indicate the presence of a few prominent negative-parity K^p = 1^-\ensuremath K^{\pi} = 1^{-} states in the 2.0-4.0MeV energy interval. The occurrence of the negative-parity dipole states with the rather high B(E1) value less than 4MeV shows the necessity of explicit parity measurements for the correct determination of the scissors mode strength in ²³²Th , ²³⁶U , and ²³⁸U isotopes.     

Reconstruction of some cosmological models in <Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>,<Emphasis Type="Italic">T</Emphasis>) cosmology

In this paper, we reconstruct cosmological models in the framework of f(R,T) gravity, where R is the Ricci scalar and T is the trace of the stress-energy tensor. We show that the dust fluid reproduces ΛCDM, phantom–non-phantom era and phantom cosmology. Further, we reconstruct different cosmological models, including the Chaplygin gas, and scalar field with some specific forms of f(R,T). Our numerical simulation for the Hubble parameter shows good agreement with the BAO observational data for low redshifts, z<2.     

Hawking radiation of <Emphasis Type="Italic">E</Emphasis> < <Emphasis Type="Italic">m</Emphasis> massive particles in the tunneling formalism

We use the tunneling formalism to calculate the Hawking radiation of massive particles. For E ≥ m, we recover the traditional result, identical to the massless case. But E < m particles can also tunnel across the horizon in a Hawking process. We study the probability for detecting such E < m particles as a function of the distance from the horizon and the energy of the particle in the tunneling formalism. We derive a general formula and obtain simple approximations in the near-horizon limit and in the limit of large radii.