Effects of 8B size on the low-energy 7Be(p,γ)8B cross section

We calculate several “size-like” ⁸B observables within the microscopic three-cluster model and study their potential constraints on the zero-energy astrophysical S₁₇(0) factor of the ⁷Be(p,γ)⁸B reaction. We find within our three-cluster model that a simultaneous reproduction of the experimental data for the ⁸B radius and quadrupole moment and of the ⁸B⁸Li Coulomb displacement energy implies S₁₇(0) = (23–25) eV b.     

Radiation widths of resonances in the <Superscript>40</Superscript>Ar(pγ)<Superscript>41</Superscript>K reaction

The excitation function for the ⁴⁰Ar(pγ)⁴¹K reaction at the accelerated proton energy E _p= 450–2700 keV is studied. Positions of 168 resonances identified as levels of the ⁴¹K nucleus are observed in this energy range. The data for the proton energy E _p < 1 MeV and E _p > 2 MeV are obtained for the first time. Relative yields of γ rays observed in the decay of the resonances are calculated from a comparison with the yield of the calibrating resonance at E _p= 1102 keV. Total radiation widths of the resonances are calculated on the basis of the data obtained.     

Energy dependence of the n-γ angular correlation in the <Superscript>9</Superscript>Be(α, nγ)<Superscript>12</Superscript>C reaction

A technique for selecting the parameters required for describing the angular correlation function and finding their energy dependence has been developed. Joint analysis of a Doppler-broadened 4.44 MeV γ lineshape from the ⁹Be(α, nγ)¹²C reaction in the range 1.9–4.5 MeV of E _α energies and with n- and γ-angular distributions was performed. The Doppler-broadened lineshapes were modeled and compared using data measured in the JET plasma experiment. Relativistic effects were analyzed.     

Nuclear vertex constants for the virtual decay <Superscript>7</Superscript>Be → <Superscript>3</Superscript>He + <Superscript>4</Superscript>He of the 7Be bound states from a phase-shift analysis in the effective-range theory

The phase-shift-analysis data for the ³He⁴He scattering are analyzed using the effective-range theory, with the Coulomb interaction taken into account. We find both the renormalized nuclear vertex constants for the vertex ⁷Be → ³He + ⁴He in the ground (3/2⁻) and in the first excited (1/2⁻) bound states of ⁷Be, and the corresponding asymptotic normalization constants of the radial wave functions in these states. The results obtained can be used in an astrophysical S-factor calculation for radiative capture reaction ⁴He(³He, γ)⁷Be     

The resonance-like structure observed in the <Superscript>40</Superscript>Ar(pγ)<Superscript>41</Superscript>K reaction

The excitation function of the ⁴⁰Ar(pγ)⁴¹K reaction in the energy range of accelerated protons E _p = 1.0–3.0 MeV was measured. Twelve new resonance states were revealed in the range E _p > 2.6 MeV. The strengths of all measured resonances were determined (for more than 200 states). A resonance-like structure with a center of gravity of 10.2 ± 0.5 MeV was identified; this agrees with the dependence of the center of gravity of the resonance-like structure found earlier on A in the nuclei of the sd shell.     

Study of ground states of <Superscript>3</Superscript>H, <Superscript>3,4,6</Superscript>He, <Superscript>6</Superscript>Li,and <Superscript>9</Superscript>Be nuclei by Feynman’s continual integrals method

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.     

Microscopic study of the low-energy 7Be(p,γ)8B reaction

We have performed a microscopic study of the ⁷Be(p,γ)⁸B reaction at low energies within the framework of the resonating group method. At solar energies, E=20 keV, we find an astrophysical S-factor of 0.0254 keV b which is in agreement with the value currently adopted in solar model calculations.     

Evaluated integral cross sections of the <Superscript>7</Superscript>Li(<Emphasis Type="Italic">p</Emphasis>, α)<Superscript>4</Superscript>He reaction

New data on the energy dependence of integral cross sections of the ⁷Li(p, α)⁴He reaction are obtained to develop the SaBa (Sarov Base) library of evaluated and experimental nuclear data at the Russian Federal Nuclear Center, All-Russia Research Institute of Experimental Physics [1]. The sum of smooth and resonance parts is used as an approximating function in the current version of the SaBa database. The smooth part is described by cubic splines. Lorentzians are used to describe resonance regions. Experimental data already available in the SaBa library are analyzed to obtain new evaluated data on the ⁷Li(p, α)⁴He reaction, and a search is conducted for new data in domestic and foreign literary sources.     

Isomeric ratios of (γ,p) and (γ,α) reactions on <Superscript>117<Emphasis Type="Italic">m,g</Emphasis></Superscript>In

The isomeric ratios of the (γ,p) and (γ,α) reactions on ^117m,g In have been measured. The ratios Y _m /Y _g was found to be 1.18(9) and 0.23(9), respectively, at a boundary energy of 22 MeV. The statistical character of the reactions under such conditions is shown.     

Measurement of the cross section for the reaction <Superscript>20</Superscript>Ne(<Emphasis Type="Italic">n,α</Emphasis>)<Superscript>17</Superscript>O in the neutron-energy between 4 and 7 MeV

The cross section for the reaction ²⁰Ne(n, α)¹⁷O was measured in the neutron-energy range 4–7 MeV. An ionization chamber equipped with a Frisch grid combined with a pulse-shape digitizer was used as a detector. Gaseous neon that served as a target on which the reaction being studied proceeded was added to the gas filling the ionization chamber. The partial cross sections for the α ₀, α ₁, α ₂, and α ₃ channels of the reaction ²⁰Ne(n, α)¹⁷O were obtained for the first time.     

Investigation of <Superscript>6</Superscript>He yield in <Superscript>7</Superscript>Li(γ, <Emphasis Type="Italic">p</Emphasis>) reaction with 22 MeV electron beam

The possibility of producing exotic ⁶He nuclei in the ⁷Li(γ, p) reaction with 22 MeV electron beam at the MT-25 microtron in the Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research (FLNR JINR), is studied. The ⁶He yield from the Li₂CO₃ target made up 6 × 10⁵ s⁻¹ per 1 μA of the electron beam current. The obtained result is quite promising, taking into account the further improvement of the target unit, the possibility of using another lithium compound, and the increase in the target material temperature and the electron beam current up to 20 μA. The application of this approach for the further production of a monochromatic beam of accelerated ⁶He nuclei with an intensity on the order of 10⁷ s⁻¹ would make a large number of experiments on investigating the structure of this nucleus and the mechanisms of nuclear reactions with its participation feasible. This method for obtaining ⁶He nuclei may turn out to be one of the most optimal (and inexpensive) currently available.     

The resonance-like structure observed in the <Superscript>25</Superscript>Mg(p, γ)<Superscript>26</Superscript>Al reaction

The gamma decay of resonance-like structure (RLS) observed in the ²⁵Mg(p, γ)²⁶Al reaction in the region of excitation energies of 7–9 MeV is studied, and the excitation function of this reaction is measured. The resonance transition strengths of states in the 1.4–2.0 MeV range of accelerated proton energies are determined. The resulting strength distributions of M1 transitions between the resonance states and the low-lying bound states in ²⁶Al are of a resonance nature. The position of the center of gravity of magnetic dipole resonance for the ground state in ²⁶Al is 7.92 MeV, and the total MDR transition strength is 5.7 MeV × μ _N ² .     

Photonuclear channel of <Superscript>7</Superscript>Be production in the Earth’s atmosphere

Measurements of average values of cross sections for the A(γ,X)⁷Be photonuclear reactions on nitrogen, oxygen, and carbon of natural isotopic composition were performed in the energy range from the threshold to 90 MeV. On the basis of the measured cross sections for ⁷Be photoproduction and on the basis of the results obtained by simulating the nuclear-electromagnetic cascade in the Earth’s atmosphere, the contribution of the photonuclear mechanism to the production of the cosmogenic radioisotope ⁷Be in the atmosphere and its latitude dependence were investigated for the first time. It is shown that the contribution of the photonuclear mechanism is commensurate with the contribution of the proton and neutron mechanisms of 7Be production in the atmosphere and that the inclusion of this mechanism is mandatory in analyzing the accumulation and transfer of ⁷Be in the planetary boundary layer.     

Investigation of the <Emphasis Type="Italic">n-γ</Emphasis> angular correlation in the <Superscript>9</Superscript>Be(α,nγ)<Superscript>12</Superscript>C reaction by analysis of the 4.44-MeV <Emphasis Type="Italic">γ</Emphasis>-line shape

A method for evaluating the angular correlation function (ACF) of neutrons and γ quanta produced in nuclear reactions has been developed based on the analysis of Doppler-broadened γ-line shapes. The lineshape analysis of the 4.44-MeV_γ line from the ⁹Be(α, nγ)¹²C reaction at E _α = 4.03 MeV and θ_γ = 0°, 15°, 30°, ..., 150°, taking into account the angular n and γ angular distributions, made it possible to unambiguously fit the ACF parameters. In view of the importance of this reaction for γ diagnostics of plasma, the γ-line shape has been calculated for the monoenergetic component of isotropic α-particle distribution, characteristic of d-t experiments.     

Breakup of 8B and the 7Be(p, γ)8B reaction

The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the ⁷Be(p, γ)⁸B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain as various measurements differ from each other by 30–40%. The Coulomb dissociation process which reverses the radiative capture by the dissociation of ⁸B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages (like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis of the breakup of ⁸B and discuss the current status of the low-energy cross sections (or the astrophysical S-factor) of the ⁷Be(p, γ)⁸B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested. Work supported by EPSRC, UK, grant nos J/95867 and L/94574.     

Investigating the excitation of 8<Superscript>−</Superscript> isomers in the odd-odd nuclei of <Superscript>116–120</Superscript>Sb in the (<Emphasis Type="Italic">p,n</Emphasis>)-reaction

Isomeric cross-section ratios in ^116m,g Sb, ^118m,g Sb and ^120m,g Sb were measured in the (p, n)-reaction for an energy of protons of ∼6.7 MeV. Experimental values of σ ^m /σ ^g were obtained: (4.6 ± 0.4) × 10⁻⁴ for ¹¹⁶Sb, (5.4 ± 0.6) × 10⁻³ for ¹¹⁸Sb and (7.4 ± 0.7) × 10⁻³ for ¹²⁰Sb. Experimental values of the isomeric crosss-ection ratios are compared to the theoretical values calculated using the TALYS-1.0 code. The statistical nature of the (p, n) reaction is demonstrated in the excitation region of residual nuclei 0.8–3.5 MeV.     

Investigation of the reaction D(<Superscript>4</Superscript>He, γ)<Superscript>6</Superscript>Li at ultralow energies

The cross section of the reaction D(⁴He, γ)⁶Li with titanium and zirconium deuterides as targets is measured for incident ⁴He⁺ ion energies of 30 and 36 keV, respectively. The ion beam is generated by a Hall pulsed plasma accelerator. For the first time, upper limits on the cross section of the reaction D(⁴He, γ)⁶Li at ultralow energies are imposed (at 90% confidence level): σ ≤ 1.2 × 10^?35 cm² for the TiD₂ target and E(⁴He⁺) = 30 keV, and σ ≤ 7 × 10^?36 cm² for the ZrD₂ target and E(⁴He⁺) = 36 keV