A study of 14N using the 13C(d,n)14N reaction

Absolute differential cross sections for the ¹³C(d, n)¹⁴N reaction were measured at deuteron bombarding energies of 4.5, 5.0 and 5.5 MeV. Spectroscopic factors and statistical compound-nucleus contributions are obtained by treating the observed cross sections as an incoherent sum of distorted-wave Born approximation and compound-nucleus contributions. Energy-averaged spectroscopic factors are derived. An anomaly is observed in the yield for the 2.313 MeV T= 1 state.     

Charge exchange reaction 14C(6Li, 6He)14N

Angular distributions of the charge exchange reaction ¹⁴C(⁶Li, ⁶He)¹⁴N leading to the 1⁺ ground state and 3.95 MeV 1⁺, and 5.20 MeV 2^? excited states at the 34 MeV incident beam energy were analyzed and measured. The 62 MeV data of Goodman et al. were also reanalyzed. The direct one-step charge exchange caused by the spin-isospin dependent term in the two-body interaction can account well for the observed data. The strength of spin-isospin dependent effective interaction (gaussian form with a range parameter of 1.8 fm) was extracted to be 18.5 MeV.     

A study of the 51V(6Li,d)55Mn reaction

Alpha particle spectroscopic strengths extracted for transitions to low-lying levels in ⁵⁵Mn observed in a study of the ⁵¹V(⁶Li, d) reaction at 32 MeV are compared with the results of shell-model calculations. These reproduce well the relative strengths of the levels.     

The reaction 14C(3He,n)16O and the coexistence model of 16O

The reaction ¹⁴C(³He, n)¹⁶O has been measured at a ³He bombarding energy of 25.4 MeV. The zero-degree differential cross section for the excitation of the three low lying 0⁺T = 0 states, at energies 0.0, 6.05 and 12.05 MeV are, respectively, 1.33 ± 0.10, 0.49 ± 0.10, and 0.50 ± 0.10 mb/sr These measured cross sections are in rough agreement with single-step zero-range DWBA calculations using an empirically determined ¹⁴C ground state wave function and in which the Brown and Green coexistence-model wave functions are used to describe the ¹⁶O 0⁺ states. The angular distribution of the transition to the ground state is measured between 0° and 32°.     

Linear momentum transfer in the reaction 232Th(14N,light particles) AT 208 MeV

The longitudinal momentum transferred to a target nucleus (ΔP) has been studied for light-particle emission in the ¹⁴N-induced reaction on ²³²Th at 208 MeV. The transferred momentum was deduced by measuring folding angles between two fission fragments resulting from the sequential decay of the target-like nucleus. It was found that the fraction $\text{?}{}_2\text{=}\text{(〈ΔP〉 + P}{}_{\mathrm{<mtext>out</mtext>}}{}^{\mathrm{\parallel }}\text{)}\text{P}{}_{\mathrm{<mtext>beam</mtext>}}$ averaged over light-particle energy was about 0.68, almost independent of light-particle species and detection angle, where P_beam is the initial momentum of the beam particle and P_out^∥, the momentum component parallel to the beam carried away by the observed light particle. A possible mechanism for describing the phenomena is discussed.     

The 93Nb(p,d)92Nb reaction at 26.3 MeV

The ⁹³Nb(p, d)⁹²Nb reaction was studied at a proton energy of 26.3 MeV. Angular distributions were obtained for outgoing deuterons to 37 states in ⁹²Nb up to an excitation energy of 4.2 MeV. The results were compared with DWBA calculations to extract l-values and spectroscopic factors. Fourteen previously unobserved l = 1 transitions were measured.     

Scattering and reactions of 14C + 14C and 14C + 14C

We have studied elastic scattering, inelastic scattering and several transfer channels of the systems ¹⁴C + ¹⁴C and ¹⁴C + ¹²C over a wide range of energies up to E_c.m. = 35 eMeV and 32 MeV, respectively. The reaction channels were identified by means of kinematic coincidences between solid-state detectors, γγ coincidences were measured to determine cross sections for mutual inelastic scattering of ¹⁴C + ¹⁴C.Pronounced regular gross structures, similar to those found for ¹⁶O + ¹⁶O, are observed in the elastic excitation function of ¹⁴C + ¹⁴C at θ_c.m. = 90°, The angular distributions measured at the energies of the maxima and an optical-model analysis suggest that one or a few surface partial waves dominate the scattering behaviour. Correlated structure of narrower width is found in the inelastic channels and, to a lesser degree, in the transfer channels which appear with rather small cross sections.In ¹⁴C + ¹²C elastic scattering the gross structures are strongly fragmented, in contrast to ¹⁴C + ¹⁴C but similar to ¹²C + ¹²C. While the ¹²C(2⁺) excitation is very weak, the observed strengths of the ¹⁴C(3^?) excitation and of neutron transfer point to a substantial role of these channels as coupling partners to the elastic configuration and to their influence on the elastic scattering behaviour. A correlated intermediate structure is observed near 23.5 MeV, where a dominance of l = 18 is suggested by the elastic scattering angular distribution. This unexpectedly high l-value exceeds l_graz at this energy by at least two units of ?.     

On the decay of the photo resonance in 14N and 14C nuclei

The decay of the photo resonances in ¹⁴N and ¹⁴C nuclei is analyzed in terms of the shell model with intermediate coupling. Cross sections and branching ratios of nucleon channels are compared with experimental data. Successive decay branches are estimated.     

The 14C(p, γ0)15N cross section below Ep = 12 MeV

The cross section for the ¹⁴C(p.γ₀)¹⁵N reaction has been measured up to E_p = 12 MeV. These measurements cover the region of the main component of the giant dipole resonance in ¹⁵N previously observed in the inverse ¹⁵N(γ, p₀)¹⁴C reaction. The structures seen are compared to recent measurements of the ¹⁴N(p, γ₀)¹⁵O cross section at corresponding energies in ¹⁵O, allowing clear identification of $\text{T =}\text{1}\text{2}\text{and}\text{3}\text{2}$ states. A comparison of the present experimental results is also made to recent bound and continuum shell model calculations for this region of ¹⁵N.     

Study of 20Ne(3He,n)22Mg at 3He energies between 2.6 and 4.0 MeV

The ²⁰Ne(³He, n) reaction leading to the ground state of ²²Mg has been investigated in the ³He⁺ energy range of 2.6 to 4.0 MeV. Angular distributions were determined with a neutron time-of-flight spectrometer at average incident energies (lab) of 3.27, 3.69, and 4.01 MeV between 0° and 120° (lab). Excitation functions for the energy region were measured at 0° and 80° (lab). The observed differential cross sections are explained by coherent contributions from direct interaction and compound-nucleus formation. A spectroscopic factor was extracted for the DWBA calculation from the absolute cross-section measurements and found to be $\text{? = 0.43±0.21}$. Resonances in the compound-nucleus formation were found at 3.00 and 3.33 MeV (c.m.) with widths of 0.28 and 0.21 MeV and spins of $\text{5}\text{2}{}^{\mathrm{+}}\text{and}\text{1}\text{2}{}^{\mathrm{?}}$, respectively.     

The reaction 14C(6Li, 6He)14N and the distribution of Gamow-Teller strength

We find that the correlation between the L=0 component of the (⁶Li, ⁶He) reaction and the GT matrix element holds down to a very low level of GT strength, and that essentially all (90%) of the GT strength lies in the 3.95 MeV state of ¹⁴N.     

The reactions 50,52Cr(d, 6Li) 46,48Ti at Ed = 651 MeV

The ^50,52Cr(d, ⁶Li) ^46,48Ti reactions have been studied at E_d = 65 MeV bombarding energy. Angular distributions of outgoing Li particles were measured for final states in ^46,48Ti nuclei from 15° to 50° (lab). These were compared with zero-range and finite-range DWBA calculations in an α-cluster pick-up approximation to obtain relative α-spectroscopic factors.     

Absolute cross sections for the 6Li(p, 3He)4He reaction at energies below 1 MeV

Total cross sections and angular distributions in the ⁶Li(p,³He)⁴He reaction have been measured over the energy range E_p = 100?700 keV. The extrapolation of the cross section to the energy region which is of interest in controlled thermonuclear reactors is given. The values of the “astrophysical S-function” are deduced from the cross sections.     

Investigation of states in 30P via the 30Si(3He,t)30P reaction at 30 MeV

The ³⁰Si(³⁰He, t)³⁰P reaction has been measured for about 100 levels in ³⁰P with E_x < 8.8 MeV. Little selectivity in the population of states has been observed. For 75 levels angular distributions have been analysed using a “fingerprint method” by determining the L-value from a comparison in shape with transitions to states with known J^π. For possible mixed L-transitions a dominance of the higher L-value is observed for almost all cases. Coulomb displacement energy calculations utilizing shell-model wave functions have been used to identify T = 1 states.     

Mass 2 and 3 cluster structure study with quasi-free reactions induced by 58 MeV protons on 9Be, 12C and 14N

Cross sections for (p, pd) and (p,p³He) reactions at 58 MeV have been measured for ⁹Be, ¹²C and ¹⁴N targets. An energy resolution of about 400 keV permitted identification of several excited states in the different residual nuclei. The experimental results are presented and analysed in the framework of the distorted-wave impulse approximation. Spectroscopic and mechanism information is discussed. Some additional quasi-free reactions involving t, ³He and α structure of ⁹Be have been observed and are also reported.     

Cross section of the reaction 6Li(p, γ)7Be

The cross section of the reaction ⁶Li(p, γ)⁷Be has been measured using Ge(Li) γ-ray spectrometers for proton bombarding energies E_p from 200 keV to 1200 keV. At E_p = 800 keV, the total (p, γ) integrated cross section is found to be 3.1 ± 0.4 μb. The cross section adopted from consideration of this and previous measurements is in good agreement with that predicted from the known thermal neutron cross section for ⁶Li(n, γ)⁷Li on the assumption that properties of mirror direct capture reactions can be well described by optical potentials that use the same parmeter values for the two reactions.     

Unnatural parity levels populated in the 16O(6Li,d)20Ne reaction

The ¹⁶O(⁶Li, d)²⁰Ne reaction to the 2^?, 4.97 MeV, 3^?, 5.63 MeV, and 4^?, 7.01 MeV members of the K^π = 2^? band has been studied. Angular distributions were measured at 32 MeV from 7.5° to 145° (lab). Excitation functions were measured at 15° (lab) and 145° (lab) from 31 to 33 MeV and 31.75 to 32.5 MeV, respectively. Results of multi-step and compound nuclear calculations are compared to the data. At this incident energy, both mechanisms appear to contribute to the population of the unnatural parity levels.     

A study of the 90Zr(6Li, 6He)90Nb reaction at E6Li = 93 MeV

The energy spectra of ⁶He nuclei from the ⁹⁰Zr(⁶Li, ⁶He) reaction at E_{⁶Li = 93 MeV} have been measured over the angular range of 7 ° ? θ_lab ? 20 °. The theoretical DWBA analysis of these spectra and angular distributions was performed employing transition densities of bound and resonance states obtained on the basis of the theory of finite Fermi systems. It is shown that up to excitation energies of E_x ≈ 10 MeV in ⁹⁰Nb a direct charge-exchange mechanism dominates in this reaction, while at higher E_x the contribution made by multistep processes increases significantly. It is also shown that the quasi-elastic cross section is determined by a sum of partial contributions of spin-isospin-flip transitions with multipolarities L=0 through L=6.     

An accurate measurement of the 7Li(d,p)8Li excitation function from Ed = 0.6 MeV to 2.0 MeV

The excitation function for the ⁷Li(d, p)⁸Li reaction was determined at incident deuteron energies ranging from 0.613 to 1.948 MeV by measuring delayed α-particles. This excitation function revealed resonances at 0.773 ± 0.010 MeV and 1.025 ± 0.010 MeV with cross sections of 181 ± 8 mb and 168 ± 7 mb, respectively. No resonance was observed in the region of 1.4 MeV.