Cross section and analyzing powers for the reaction p3H → γ4He at Ep = 227, 300 and 375 MeV

Cross sections and analyzing powers for the radiative capture of polarized protons by tritium have been measured at energies of 227, 300, and 375 MeV. The cross-section results are in good accord with data taken for the inverse photodisintegration reaction assuming detailed balance which indicates there is no violation of time-reversal invariance. The experimental results are compared with distorted wave impulse approximation calculation and it is found that the inclusion of meson exchange current effects is important in this energy range.     

Study of the reaction 12C(γ, n 3He)2α

The possibility of separating, with the aid of photoemulsion, channels of the reaction ¹²C(γ, n ³He)2α that involve the formation of ⁷Be and ⁸Be intermediate nuclei in excited states is studied. The experimental energy distributions of these nuclei are obtained. The relative yields from these reaction channels are estimated.     

The mechanism of the 7Li(d, 2α)n reaction from Ed = 3 to 15 MeV

The ⁷Li(d, 2α)n reaction proceeds almost entirely through excitation and sequential decay of the 16.63 and 16.92 MeV levels in ⁸Be, for incident energies 1 to 13 MeV above their threshold. The energy dependence for forming these levels with the neutron emitted at 0° is approximately that predicted assuming the neutron is a spectator from the incident deuteron. None of the individual spectra, the angular dependence of the cross section at fixed E_d, or the bombarding-energy-dependence of the cross section for forming the levels is consistent with the involvement of a spectator neutron from the ⁷Li target.     

Quasi-free processes in 6Li(3He,pα)4He reaction at low energies

The ⁶Li(³He, pα)⁴He reaction was studied experimentally at 3.5, 4.4 and 5.5 MeV in the quasi-free reaction kinematical region. The effects of a resonance in the virtual ²H(³He, p)⁴He reaction on the three-body reaction cross section were investigated.     

The 12C(γ,p) reaction at Eγ = 60 and 80 MeV

The tagged photon technique has been used to measure the ¹²C photoproton cross section over the angular range θ_p = 30°–135° for E_γ = 60 and 80 MeV. Comparison of the results with quasifree knockout and quasideuteron calculations shows that photon interaction with two-nucleon pairs is dominant at least for high excitation energies in the residual nucleus.     

Photodisintegration cross section of the reaction (4)He(γ,p)(3)H between 22 and 30 MeV

The two-body photodisintegration cross section of (4)He into a proton and triton was measured with monoenergetic photon beams in 0.5 MeV energy steps between 22 and 30 MeV. High-pressure (4)He-Xe gas scintillators of various (4)He/Xe ratios served as targets and detectors. Pure Xe gas scintillators were used for background studies. A NaI detector together with a plastic scintillator paddle was employed for determining the incident photon flux. Our comprehensive data set follows the trend of the theoretical calculations of the Trento group very well, although our data are consistently lower in magnitude by about 5%. However, they differ significantly from the majority of the previous data, especially from the recent data of Shima et al. The latter data had put into question the validity of theoretical approaches used to calculate core-collapse supernova explosions and big-bang nucleosynthesis abundances of certain light nuclei.     

Study on the 208Pb(α, 6He)206Pb reaction at Eα = 109 MeV

The ²⁰⁸Pb(α, ⁶He)²⁰⁶Pb reaction induced by 109 MeV α particles has been studied with 70 keV energy resolution. Twenty-five transitions up to 6.2 MeV in excitation energy have been analyzed. The shapes of the angular distributions are reproduced well by the zero-range distorted-wave Born approximation (DWBA) calculations. The spin and parity of the level at 6.10 MeV are proposed to be 9⁻. It is interpreted as a weakly-coupled state of the collective 3⁻ state and the two-hole 6⁺ shell-model state.The energy dependence of the total cross sections of the (α, ⁶He) and (p, t) reactions has been studied systematically by using our present data and other data from the literatures. It reveals that there exists an empirical rule which allows one to compare quantitatively the ratios of the transition strengths of both reactions. The transition strength of the (α,⁶He) reaction is found to be about 35 times smaller than that of the (p, t) reaction for the transitions to the natural parity states, while it is about 15 times smaller for the transition to the unnatural parity 3⁺ state. These small transition strengths are explained by the fact that this reaction occurs at the surface region of the nucleus.     

Tensor Force Manifestations in ab Initio Study of the 2H(d, γ)4He, 2H(d, p)3H, and 2H(d, n)3He Reactions

The ²H(d, γ)⁴He capture reaction and the ²H(d, p)³H and ²H(d, n)³He transfer reactions at very low energies are studied in an extended microscopic cluster model with a realistic nucleon–nucleon force. Our results show that the tensor force in realistic interactions plays an essential and indispensable role to reproduce the very low-energy astrophysical S factor of these reactions.     

Tensor force manifestations in ab initio study of the 2H(d,γ)4He, 2H(d,p)3H, and 2H(d,n)3He reactions

The (2)H(d,p)(3)H, (2)H(d,n)(3)He, and (2)H(d,γ)(4)He reactions are studied at low energies in a multichannel ab initio model that takes into account the distortions of the nuclei. The internal wave functions of these nuclei are given by the stochastic variational method with the AV8' realistic interaction and a phenomenological three-body force included to reproduce the two-body thresholds. The obtained astrophysical S factors are all in very good agreement with the experiment. The most important channels for both transfer and radiative capture are identified by comparing to calculations with an effective central force. They are all found to dominate thanks to the tensor force.     

The 13C(p̄, d)12C reaction at 119 MeV

Differential cross sections and analysing powers for transitions to many residual states of ¹²C below 20 MeV excitation energy have been measured for the (p̄, d) reaction on ¹³C at 119 MeV. Distorted wave Born approximation calculations using either adiabatic or conventional deuteron elastic scattering potentials were unable to adequately reproduce the cross-section and analysing power data for the strongest observed transitions. In order to improve the fits to both these sets of data it was necessary to include an imaginary spin-orbit term in the deuteron potential. The spectroscopic factors deduced in this analysis are, however, smaller than theoretical predictions. The mechanisms for the population of the observed weak residual states are discussed semi- quantitatively, and for the higher excitation energy region, a comparison to the known level structure of ¹²C is made.     

Cross Section Measurements for (n,2n),(n,p)and (n,α) Reactions on Strontium Isotopes at the Neutron Energy About 14MeV

Cross-sections for ⁸⁴Sr(n, 2n)⁸³Sr, ⁸⁶Sr(n, 2n)^{85mSr,86Sr(n, 2n)85Sr,88Sr(n, 2n)87mSr,84Sr(n, p)84Rb,86Sr(n, p)86Rb, 88Sr(n, p)88Rb and 88Sr(n,α)85mKr reactions were measured at neutron energies from 13.5 to 14.6MeV using activation technique and γ-ray spectrometry. The neutron flux was determined using the monitor reaction 93Nb(n, 2n)92mNb and the neutron energies were measured by the method of cross section ratios for $^{90}$Zr(n, 2n)$^{89m+g}$Zr to $^{93}$Nb(n, 2n)$^{92m}$Nb reactions. The results of present work were compared with data published previously.}     

Study of the 24Mg(α, 12C)16O reaction in the energy range Elab = 24.9–27.76 MeV

The ²⁴Mg(α,¹²C)¹⁶O and ²⁴Mg(α, α')²⁴Mg reactions have been used to search for resonances in the ²⁸Si compound nucleus. The excitation functions were measured in the energy range between 24.9 and 27.76 MeV. Angular distributions of ¹²C nuclei and elastic and inelastic scattering of α-particles have been measured at energies corresponding to extrema of excitation functions. Significant anomalies have been found at E_ex = 31.5 and 33,1 MeV. The spins and parities of these structures are assigned as 9⁻ and 11⁻, respectively.     

Production of the isotope 18F in the reaction 23Na(γ,αn)18F at E b = 55 MeV

The activity of ¹⁸F that was produced in the ²³Na(??,??n)¹⁸F reaction with the maximum bremsstrahlung energy E _b = 55 MeV was measured.     

Measurement of the astrophysical S factor for the low energy 2H(d,γ)4He reaction

The y-rays and protons from an Ed = 20 keV deuteron beam incident on a D-Ti target were measured. A branching ratio of the 2H(d,T)4He reaction versus the 2H(d,p)aH reaction of F.v/l'p = (1.06+ 0.34) x 10-7 has been obtained, and the astrophysical S factor of the 2H(d,T)aHe reaction at the center of mass energy Ecru ≈ 7 keV of (6.0+2.4) x 10-8 keV.b was deduced.     

A contribution to direct processes in the Co59(p,n) reaction forE p ∼ 6·5 MeV

Nuclear emulsions were used to study the energy spectrum and forward-backward asymmetry of neutrons from the Co⁵⁹(p,n) reaction forE _p 6·5 MeV. It was found that the decay of the compound nucleus makes a maximum contribution of 50% to the reaction yield. Energies of some excited states of the Ni⁵⁹ nucleus were also determined.

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Co⁵⁹(p,n) E _p 6,5 MeV

- Co⁵⁹(p,n) E _p 6,5 MeV. , 50%. , Ni⁵⁹.

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The authors would like to thank all those who helped in this work, particularly all members of the cyclotron group of the Nuclear Research Institute of the Czechoslovak Academy of Sciences, who so willingly helped with the irradiation, and H. Koutová from the Faculty of Technical and Nuclear Physics, who carefully measured the emulsions. Our thanks are also due to R. Krejová from the Faculty of Technical and Nuclear Physics for developing the emulsions and J. Kopecký from the Nuclear Research Institute for providing the cobalt target.     

Antisymmetry and channel coupling contributions to the absorption for p+αd+3He

To understand recently established empirical p+α potentials, RGM calculations followed by inversion are made to study contributions of the d+³He reaction channels and deuteron distortion effects to the p+α potential. An equivalent study of the d+³He potential is also presented. The contributions of exchange non-locality to the absorption are simulated by including an phenomenological imaginary potential in the RGM. These effects alone strongly influence the shape of the imaginary potentials for both p+α and d+³He. The potentials local-equivalent to the fully antisymmetrised-coupled channels calculations have a significant parity-dependence in both real and imaginary components, which for p+α is qualitatively similar to that found empirically. The effects on the potentials of the further inclusion of deuteron distortion are also presented. The inclusion of a spin-orbit term in the RGM, adds additional terms to the phase-equivalent potential, most notably the comparatively large imaginary spin-orbit term found empirically.