MeV Incident Proton Energy Research Articles

Study of structure in the 28Si(p, n) 28P and 28Si(p, α) 25Al excitation functions

The 28Si(p, n) 28P and 28Si(p, α) 25Al reactions have been studied over the energy range of 16.0 to 18.2 MeV incident proton energy. Fluctuations appear in the excitation functions over the entire range with widths of 100 keV and 48 keV for the neutron and alpha channels, respectively. The energy averaged 28Si(p, α) 25Al angular distributions are not reproduced by Hauser-Feshbach compound nucleus calculations but do resemble DWBA calculations. Because of the complex nature of the reaction mechanism in this energy range, it could not be concluded whether the structure in the excitation functions is due to doorway states or Ericson fluctuations.

Étude des niveaux de 56Fe excités par les réactions (p, p′γ) ET (n, n′γ)

The energy levels of 56Fe have been studied by means of the (p, p′γ) and (n, n′γ) reactions. Particle-gamma coincidences from the 56Fe(p, p′γ) reaction have been measured at 6.5, 8, 10 and 11 MeV incident proton energies. The coincident γ-rays were detected with a 100 cm 3 Ge(Li) detector and protons with cooled Si(Li) diodes. Independently, absolute differential cross sections for the production of γ-rays by inelastic neutron scattering from iron have been measured in the energy range 4.8–8.8 MeV. A 65 cm 3 Ge(Li) detector surrounded by a NaI (Tl) annulus and associated with a pulsed beam time-of-flight system was used to detect the deexcitation γ-rays. By comparing the measured angular distributions and excitation functions with those calculated on the basis of the statistical theory, spin assignments for poorly known states are made. From these two experiments, a decay scheme is constructed and proposed. The results are briefly compared with mixed-configuration shell model calculations.

Complex microscopic effective interaction for (p, n) reactions

A simple recipe for generating a complex effective interaction for distorted wave Born approximation calculations from a real, microscopic charge-exchange form factor is investigated. The recipe is tested against angular distribution data for 208Pb(p, n) and 209Bi(p, n) from 25 to 50 MeV incident proton energy. The form factor resulting from the recipe is also compared qualitatively to complex effective coupling potentials, resulting from a charge-independent Lane-model formalism and from coupled-channion-channels calculations for a suggested multistep (p, d)—(d, n) reaction mechanism.

Violation of Isospin Conservation in Two-Nucleon Pickup Reactions

The analog ($p$, $^{3}\mathrm{He}$) and ($p, t$) reactions on $^{16}\mathrm{O}$ have been compared at 27.0 MeV incident proton energy. In contrast to previous results at higher energies (\ensuremath{\ge}43.7 MeV), the intensity ratio predicted by isospin conservation was satisfied only at small angles.

The 144Nd(d, p) and 144Nd(d, t) reactions and isobaric analog resonances in 144Nd(p, p 0) and 144Nd(p, p')

The reactions 144Nd(d, p) and 144Nd(d, t), at an incident deuteron energy of 12.6 MeV, have been investigated with an energy resolution of about 16 keV, and excitation functions for the reactions 144Nd(p, p 0) and 144Nd(p, p') have been measured from 9.3 to 12 MeV incident proton energies. The analysis of the analog resonances observed in the excitation functions is compared with the results of the 144Nd(d, p) experiment.

A two-arm wire chamber spectrometer for use at 30–50 MeV incident proton energies

Abstract A wire chamber spectrometer connected on-line to two computers has been developed to study reactions having two (or more) charged particles in final states at incident proton energies in the range 30–50 MeV. It consists of two wire chamber and scintillation counter hodoscopes capable of detecting protons with kinetic energues between 7 MeV and 50 MeV. The two computers are used for complete reduction of data on-line. The spectrometer has been used so far in measuring cross sections for p-p bremsstrahlung and some (p,2p) reactions.

A local versus non-local t-matrix in the 14N(p, 2p) 13C reaction at 46 MeV

The angular distributions for the 14N(p, 2p) 13C reactions at 46 MeV incident proton energy are calculated in the distorted wave t-matrix approximation (DWTA) where approximate optical-model waves are used. A comparison is made between the calculation using a local t-matrix to that of a non-local t-matrix. The (p, 2p) angular distribution is smaller in magnitude where a non-local t-matrix is employed compared to the calculation using a local t-matrix which implies that there is an overall enhancement of absorption associated with the non-local t-matrix. This also implies that differences between the local and non-local off-energy-shell effects can be significant. Parameter studies were undertaken for the distorted waves and bound state wave function and the effects on the angular distributions were similar in the local and non-local cases. The distortion effect due to the final-state focus phase dramatically changes the shape of the angular distribution. The calculations are considered to be a test of the off-energy-shell effects due to non-local interaction. This calculation is also a test of the approximate distorted waves at 46 MeV and the comparison to the 14N(p, 2p) 13C data indicates that the distortion is reasonably well described.

Absence of proton weak coupling states in93Nb

The reactions93Nb(p, p)93Nb,93Nb(p, n)93Mo, and93Nb(p, p′) through isobaric analog resonances in94Mo have been used to study the structure of low-lying93Nb states, specifically the degree to which these states can be described as single protons coupled to the core states of92Zr. Excitation curves were obtained from 5.8 to 7.6 MeV incident proton energy, for eight states in93Nb. Results of this work are compared to results from Coulomb excitation studies,93Nb(n, n′γ),93Nb(d,p),92Zr(3He,d),94Mo(d,3He) and other related work.

Measurement of polarization and differential cross section in p- 4He elastic scattering between 25 and 29 MeV

p- 4He polarization and elastic differential cross-section angular distributions have been measured at 25.0, 26.1, 27.1. 28.2 and 29.2 MeV incident proton energy. The angular distributions were measured in 5° intervals from 20° to 160° (lab) for the polarization and from 30° to 160° (lab) for the differential cross section. The polarization measurements were generally such that δ p ≦ ±0.03 whilst the differential cross-section errors were ≦3% except at forward angles. The normalization accuracies were determined to be ±1% for the polarization and ±3.5% for the differential cross section.

Nucleon-nucleon final-state interactions in the reactions 3He(p, d)2p, 4He(p, t)2p and 4He(p, 3He)pn

The energy spectra of deuterons, tritons and 3He particles from the reactions 3He(p, d)2p, 4He(p, t)2p and 4He(p, 3He)pn have been measured at angles between 6° and 60° lab. The 3He(p, d)2p reaction was studied at both 30.5 and 49.5 MeV incident proton energies, while the other two reactions were studied at 49.5 MeV only. The energy spectra are compared with calculations based on the Watson-Migdal model of final-state interactions.

Analyzing power and phase-shift analysis of proton-helium elastic scattering at 70 and 80 MeV

A helium-filled streamer chamber was used to measure the analyzing power of proton-helium elastic scattering at 70 and 80 MeV incident proton energy. Phase-shift analyses of data at 63, 70, 80 and 94 MeV yielded solutions which vary smoothly with energy and are consistent with results at lower energies.

Excitation Energy of the First Excited State ofC12, and Observation of a Coherent Doppler Effect

The excitation energy of the first ${2}^{+}$ state in ${\mathrm{C}}^{12}$ has been determined to be 4440.0\ifmmode\pm\else\textpm\fi{}0.5 keV by means of the ($p, {p}^{\ensuremath{'}}\ensuremath{\gamma}$) reaction at 23 MeV incident proton energy. $\ensuremath{\gamma}$ rays were detected by a Ge(Li) detector in coincidence with inelastically scattered protons to reduce Doppler broadening. An anomaly in which a symmetrical doublet appeared in the $\ensuremath{\gamma}$-ray singles spectrum observed at 90\ifmmode^\circ\else\textdegree\fi{} to the beam direction is explained on the basis of a coherent Doppler effect involving selective population of the magnetic sublevels of the ${2}^{+}$ state in the inelastic scattering process.

Scattering of polarized protons by deuterium in the energy region 10 to 20 MeV

The polarization of protons elastically scattered from deuterium has been measured at four energies between 10 and 20 MeV incident proton energy. The asymmetry is seen to become negative for large angles at 19.1 MeV and for small angles at 11.0 and 13.2 MeV.

Magnetic Analysis of theBe9(p, α)Li6Reaction

The momentum spectrum of the alpha particles from the Be/sup 9/(p, alpha )Li/sup 6/ reaction was measured in a magnetic spectrometer at 30 deg with 10- Mev incident proton energy. The discrete alpha-particle groups observed correspond to states in Li/sup 6/ at 0-, 2.19-, 3.55-, 4.40-, and 5.32-Mev excitation energy. Higher excited states are obscured at all angles of observation by the continuous alpha spectrum from the breakup in flight of Be/sup 8/, Li/sup 6*/, Be/sup 9*/, and B/sup 9/. ( auth)