Investigation of low-lying states of 15N via 14N(d,p)15N reactions with vector polarized deuterons

Angular distributions of cross section and vector analyzing power have been measured for the ¹⁴N(d, p)¹⁵N reaction at E_d = 10 MeV for transitions to levels up to 8.6 MeV excitation in ¹⁵N. Distorted wave Born approximation calculations and calibration curves were used to determine total and orbital angular momenta and spectroscopic factors of the transferred neutrons. The results were compared with different theoretical approaches.     

Messung der Neutronenpolarisation bei der Reaktion12C(d,n 0)13N mit Hilfe der Mott-Schwinger-Streuung

The polarization of neutrons produced in the reaction¹²C(d, n ⁰)¹³N was measured. Deuterons from the Karlsruhe isochronous cyclotron were used to induce this reaction at 51,5 MeV laboratory energy. The degree of polarization was determined by using the special features of Mott-Schwinger scattering. With an uranium scatterer analysing efficiencies of up to 0.92 can be obtained at very small angles (0.23°). The analysing efficiency can be calculated if the differential cross section at 0° and the total cross section is known. These quantities were experimentally determined. The differential cross section for 49.4 MeV neutrons, scattered by uranium, was measured between 0.88° and 2.10°. By an extrapolation the value 43.4±2.6 b/sr was found for the nuclear differential cross section at zero degree. A total cross section ofσ _t=4.80±0.22 b was obtained. The neutron polarization was measured at a reaction angle of 24.5° and the result isP=?0.45±0.07. This value is fairly above the semiclassical 1/3 limit and can be only explained, if spin orbit forces are taken into account. For (d, n) reactions this is the first neutron-polarization measurement above an energy of 20 MeV.     

The cross section of the7Be(n,p)7Li reaction at 24.5 keV neutron energy

The 24.5 keV neutrons induced reaction with the⁷Be radioactive nucleus was studied. The value of σ_np=(18±4)b was obtained for the⁷Be(n, p)⁷Li reaction cross section.     

Systematics of the mean energy and the mean multiplicity of prompt neutrons originating from 232Th fission

The cross section for the neutron-induced fission of ²³²Th target nuclei, ?? _f (E _n ), was described within statistical theory. The spectra of the mean multiplicity, $\bar v$ (E _n ), and the mean energy, $\bar E$ (E _n ), of secondary neutrons accompanying ²³²Th fission induced by neutrons of energy extending up to E _n = 20 MeV were analyzed on the basis of the chance structure of the cross section.     

Energy levels of 14C

The ⁹Be (⁶Li, p)¹⁴C reaction has been studied using 20 MeV ⁶Li ions and the Penn multiangle spectrograph. Proton groups are reported corresponding to thirty excited states of ¹⁴C with E_x < 18.2 MeV. The total cross section for formation of the six bound excited states, whose J^π are known, is proportional to 2J_f + 1. Possible new spin assignments are suggested for several unbound levels of ¹⁴C, based on the 2J_f + 1 rule and a comparison of the experimental widths and widths predicted from neutron penetration of a centrifugal barrier.     

The reactions N14(n, α)B11 and N14(n,t)C12 observed with a gridded ionization chamber

The cross sections for the reactions N¹⁴(n, α)B¹¹ and N¹⁴(n, t)C¹² have been measured in the neutron energy range 4.0 to 6.4 MeV and at 2.5 MeV. Mono-energetic neutrons were produced in the D(d, n) He³ reaction using a gas target. The (n, α) and (n, t) disintegrations were detected in a gridded ionization chamber filled with an argonnitrogen mixture. The response of the chamber under different operation conditions is described. The excitation functions, measured with a neutron energy resolution of 40 to 50 keV, are given for theα ₀ group from the N¹⁴(n,α)B¹¹ reaction over the entire neutron energy range and for theα ₁ group and the t₀ group from N¹⁴(n, t) C¹² for neutron energies above 4.3 and 5.6 MeV, respectively.     

Measurement of fast neutron induced fission cross section of thorium using Lexan plastic track detector

Fission-track registration characteristics of Lexan solid state nuclear track detectors have been used to measure the fast neutron induced fission cross section of²³²Th. The fast neutrons (?14.2MeV) were produced with the help of an AN-400 model Van-de-Graaff accelerator at Banaras Hindu University laboratory using³H(²H,n)⁴He reaction and were used to irradiate the fissile target deposited on the plastic detector. The track densityT, registered on the plastic detector is related to the fission cross sectionσ _f, through the relationT=knσ _føt wheren is the number of fissile atoms per cm² in the deposit, ø is the neutron flux,k is fission track registration efficiency andt is the time of irradiation. The fission cross sectionσ _f of²³²Th, relative to the well measured fission cross section of²³⁸U, was found to be 0.36±0.04 barn.     

Messung des totalen Wirkungsquerschnitts von27Al für schnelle Neutronen mit Si(Li)-Detektoren

The total fast neutron cross section of²⁷Al has been determined by transmission measurements using Si(Li)-solid state detectors for neutron spectroscopy. The energies of the bombarding neutrons have been in the range betweenE _n=5,24 andE _n=7,26 MeV. A comparision has been made between the total cross sections obtained in this experiment and values obtained via the time-of-flight technique. At most neutron energies the agreement was within experimental errors quoted for the works being compared.     

Proton transitions in22Na(n,p)22Ne reaction

The nuclear reactions induced by thermal and 2 keV neutrons on²²Na radioactive nucleus were studied. For the thermal neutrons a more accurate value of²²Na (n,p)²²Ne reaction cross section was obtained. A weak proton transition to the²²Ne ground state was observed. The upper limits of cross sections for thermal neutron induced (n,∞) reaction and (n, p) reaction with 2 keV neut·rons are given.     

The 17O(p, α)14N reaction: Physics and astrophysics

The nucleus ¹⁸F has been studied using the ¹⁷O(p,α)¹⁴N reaction over the energy range E_p = 400 to 1400 keV with thin Ti¹⁷O₂ targets. New resonances at E_p = 525, 688, 1015, 1276 and 1338 keV have been discovered. The strengths for all resonances in this energy range have been measured and the entire cross section in this region has been fitted using the R-matrix formalism of Lane and Thomas. Some discussion is presented concerning the values of the boundary condition parameters used in the R-matrix fit and two sets of results are presented corresponding to two different treatments of the boundary conditions.The ¹⁷O(p, α)¹⁴N cross section has been extrapolated to astrophysical energies using an R-matrix calculation incorporating the partial widths obtained from the data from E_p = 400 to 1400 keV. These results are compared with previous ¹⁷O(p, α)¹⁴N calculations and the ¹⁷O(p, γ)¹⁸F direct capture calculation of Rolfs and Rodney.     

The polarization and differential cross section of fast neutrons scattered from 6Li and an R-function analysis of the interaction below 4 MeV

The analyzing power of ⁶Li for the elastic scattering of polarized neutrons with energies between 2 and 4 MeV, has been measured at six angles ranging from 25° to 150°. The polarized neutrons were generated from the reactions Pb(γ, n) and ¹²C(n, $\text{n}$), and their polarization was measured using the double-scattering method. The neutron energies were determined with a nanosecond timeof-flight spectrometer. In addition, the differential cross section was measured at three angles in the same energy range; the cross section was determined relative to the well-known n-¹²C cross section. The present results have been combined with existing data for the neutron total, (n, α), and differential elastic cross sections, in a reduced R-function analysis. Clear evidence of a p-wave triplet of shellmodel states emerges from the analysis.     

Isospin mixing observed in the reaction 12C(6Li, α)14N

The reaction ¹²C(¹²Li, α)¹⁴N was studied to investigate the isospin mixing of high-lying levels in ¹⁸F. Excitation functions and angular distributions of the α-transitions to the ground, first and second excited states in ¹⁴N were measured for bombarding energies from 3.2 to 8.0 MeV. The isospin-forbidden cross section for the excitation of the lowest T = 1 state in ¹⁴N at 2.31 MeV was found to lie between 1–2 % of that of the allowed transitions. A partial wave analysis of the α₁ angular distribution data revealed a strong resonance with J^π = 2⁺ at E_x = 15.99 MeV. Arguments are presented which tentatively identify this resonance as being due to two close-lying 2⁺ levels with different isospin.     

Triton-emission cross sections with 30 MeV d(Be) break-up neutrons

Triton-emission cross sections were measured for Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo, Ag, Ta, Tl, Pb and Bi with a 30 MeV d(Be) break-up neutron spectrum characterized by a multiple-foil activation technique. The accumulated tritium was separated by vacuum extraction and measured by low-level gas-phase β^? counting. The systematic trend in the cross sections is somewhat similar to that in the 53 MeV d(Be) break-up neutron spectrum; apart from some initial decrease as a function of Z, the cross section is almost constant over the entire range of Z = 22 to 83. The magnitudes of the cross sections lie between those with 14 MeV neutrons and 53 MeV d(Be) break-up neutrons. Hauser-Feshbach calculations show that the statistical model describes the triton-emission cross sections for nuclei in the (2s, ld) shell within a factor of 2; for the heavier nuclei, however, the calculated cross sections are much smaller than the experimental values.     

Search for P-ODD asymmetry in the radiative cross-section of the interaction of neutrons with lead nuclei

The P-odd effect in the radiation cross section of capture of longitudinally polarized neutrons in a sample of natural lead is measured. The experiment was performed at PF1B facility at the Institut Max von Laue-Paul Langevin. The neutron polarization P _n was 92%, the total flux of polarized neutrons was ～3 × 10¹⁰ n/s, and the mean neutron wavelength was λ = 4.7 Å. Taking into account “0-test” we estimated the asymmetry: a _γ(^natPb) = (2.3 ± 3.5) × 10^?7, i.e., α _γ ≤ 8.1 × 10^?7 at 90% confidence level.     

Information from leading neutrons at HERA

In principle, leading neutrons produced in photoproduction and deep-inelastic scattering at HERA have the potential to determine the pion structure function, the neutron absorptive cross section and the form of the pion flux. To explore this potential we compare theoretical predictions for the x_L and p_t spectra of leading neutrons and the Q² dependence of the cross section with the existing ZEUS data.     

Partial differential cross section of inelastic magnetic neutron scattering in the paramagnetic phase of LaCoO3

The partial differential cross section of inelastic magnetic neutron scattering from the compound LaCoO₃ in the paramagnetic phase is studied theoretically. The contribution to scattering from the high-spin state of an ion in zero magnetic field and the modification of this contribution upon application of a magnetic field are calculated using the effective Hamiltonian for the ⁵ D term. The amplitude of the peak in the dependence of the scattering cross section on the energy of scattered neutrons, which corresponds to the transition from the low-spin to the intermediate-spin state, is estimated.     

(n, α) Reactions on light nuclei atE n =13.9 MeV

The reactions¹⁴N (n, α)¹¹B and¹⁰B(n, α)⁷Li were studied with 13.9 MeV neutrons using a counter telescope. Differential cross sections were measured for the transitions to the ground states and to some excited states. The results provide evidence for a strong contribution from a direct reaction mechanism. Systematics of integrated cross sections for the ground state transitions of all known (n, α) reactions on light nuclei with 14 MeV neutrons is also given.     

Winkelverteilung der Polarisation der Neutronen aus der Reaktion14C(d,n 0)15N bei Deuteronenenergien zwischen 1,3 und 1,9 MeV

Polarization distributions of ground state neutrons emitted from the¹⁴C(d,n ₀)¹⁵N reaction were investigated over the angular range from 15 ° (lab) to 150 ° (lab) at bombarding energies of 1.28, 1.55 and 1.88 MeV. Scattering of neutrons from helium served as polarization analyzer. The experimental results show a large variation with energy of the polarization ranging betweenP(Θ_lab=130 °)=?21% andP(Θ_lab=130 °)=+50% at 1.28 and 1.88 MeV respectively.