Angular Distributions Of Protons Research Articles

Mechanism of reactions induced by 7 MeV deuterons on9Be [(d, p), (d, d), (d, t), (d,4He)

Angular distributions of protons, deuterons, tritons and alpha-particles emitted from the reactions in thed+9Be-system atE d =7 MeV as well as excitation functions at selected angles in the energy rangeE d =6.5–7.5 MeV (LAB) were measured. The potential part of the elastic scattering is described by the phenomenological optical model. The compound nucleus contribution to all exit channels is determined using the Hauser-Feshbach model. The collective excitation of the 2.43 MeV excited state of9Be and transfer processes are analysed within the DWBA formalism. The analyses suggest a significant contribution of five-nucleon transfer to the (d,4He) channel.

Study of multiplicity and the pseudorapidity correlation in the forward and backward hemisphere for pions and protons emitted in a 12C – emulsion interaction at 4.5 A ∙ GeV/c

The paper presents an in depth study of the forward and backward pseudorapidity correlations for pions and protons produced in a 12C – emulsion interaction at 4.5 A ∙ GeV/c. The angular distribution of protons and the pseudorapidity distribution of pions are pictured. The asymmetry parameter (A) and the forward – backward ratio (F/B) are shown as a function of the number of heavy particles (nh).

The 40Cs(e,e'p 0) 39K coincidence cross section in the giant dipole resonance region

The energy spectra and angular distribution of protons from the 40Ca(e, e'p 0) coincidence reaction have been measured at angles out of the scattering plane, in the region of the giant dipole resonance. The longitudinal-transverse interference term of the electroexcitation cross section, as well as the non-interference term, have been obtained. These cross sections are in reasonable agreement with those derived from (γ,p 0) and (p, γ 0) reactions using the theory based on the two-step process through the giant resonances. The results are compared with the particle-hole model and the continuous RPA calculations.

Angular distribution of the protons from 5Lig.s. decay in the reaction

Abstract The 6 Li ( 3 He , α) 5 Li → α + p reaction has been studied at energies of 1.5, 1.73, 3.0 and 3.5 MeV. From the measurements of the alpha-proton coincidences the angular distribution of protons from the decay of the particle unstable 5 Li nucleus have been derived. They are asymmetric relative to the 5 Li recoil momentum, in agreement with earlier experiments. A possible explanation of this asymmetry is given in terms of a strong polarization of the 5 Li as is expected in an angular momentum mismatched transfer reaction.

Multiplicity, momentum and angular distributions of protons from the interactions ofp, d, α andC with carbon at 4.2 GeV/c/nucleon momentum

Average multiplicity of protons fromp, d, α andC interactions with carbon at 4.2 GeV/c/ N is shown to increase with the mass number of incident nucleus. ThisA dependence is stronger for fast protons than for the slow ones. Angular and momentum distributions are described by the Dubna Cascade Model. Some discrepancy is observed in the high momentum part of the distributions.

Spectroscopy of 14C from the 11B(α,p) 14C reaction at 118 MeV

Proton angular distributions have been measured for the 11B(α, p) 14C reaction at 118.1 MeV. DWBA calculations employing three-nucleon semi-microscopic form factors were made for states of excitation energies ranging from 6 MeV to 21.5 MeV. The weak coupling shell model wavefunctions of Lie were used in the DWBA calculations for states of 14C below 12 MeV excitation energy. For states above 14.8 MeV 3p-5h components in the 14C wavefunctions are shown to play a dominant role.

Proton and deuteron inelastic excitation of the 1(+) state at Ex=5.846 MeV in 208Pb: Isoscalar character and importance of tensor correlations.

Differential cross sections for $^{208}\mathrm{Pb}$(p,p') and $^{208}\mathrm{Pb}$(d,d') excitation of the ${1}^{+}$ state at ${E}_{x}$=5.846 MeV were measured at ${E}_{\mathrm{inc}=45}$ MeV. The fact that the measured strengths of both reactions are very similar supports the isoscalar nature of the ${1}^{+}$ state. The comparison of the experimental proton angular distribution to microscopic distorted-wave calculations using random phase approximation wave functions with and without tensor correlations suggests that the isoscalar tensor part of the (\ensuremath{\pi}+\ensuremath{\rho})-exchange potential is too strong.

Coincidence measurements of light particles and evaporation residues in the 16O+ 27Al fusion reaction

Energy and angular distributions of protons and α-particles in coincidence with fusion residues produced in the reaction of 150 MeV 16O with 27Al were measured. Experimental results are reproduced by a statistical model calculation except a forward component of α-particle yield. About 20% of the total α-particle yield is considered to originate from incomplete fusion process.

Angular distribution of polar light particles in the fission of 235-U

Abstract The angular distribution of polar light charged particles in thermal neutron-induced fission of 235-U has been measured. The angular distribution of protons is found to be very narrow compared to alpha particles and tritons.

Reactions in the9Be+9Be system at low energies

Angular distributions of protons, deuterons, tritons, alpha particles and 7Li at 7 MeV CM and 8Be at 10 MeV CM have been measured for the 9Be+9Be system. The contribution of the compound nucleus mechanism to the reactions under investigation was estimated by an analysis of the light charged particle channels. The 9Be(9Be,8Be)10Be angular distribution was compared with the predictions of the DWBA model supplemented with the incoherent compound nucleus contribution. The 10Be(GS) neutron spectroscopic factor deduced from a comparison of theoretical and experimental cross sections at small angles was found to be consistent with the theoretical value given by Cohen and Kurath, (1967).

States in 163Dy and 169Er populated in the (t, p) reaction

Angular distributions of protons from the 161Dy(t, p) 163Dy and 167Er(t, p) 169Er reactions were studied, using 15 MeV and 17 MeV tritons from the McMaster University tandem Van de Graaff accelerator. The reaction products were analyzed with a magnetic spectrograph and detected with nuclear emulsions. Since the 161Dy target ground state is the 5 2 +[642] orbital, a strong L = 0 transition was observed to the 5 2 +[642] bandhead in 163Dy, which was previously assigned at 251 keV. Also transitions to the 7 2 , 9 2 and 11 2 band members were observed. Similarly, a strong L = 0 transition was observed to the 7 2 +[633] bandhead at 244 keV in 169Er, with the other band members only weakly populated. The angular distributions to the various members of these two bands can be described when higher-order reaction processes are taken into account. In 163Dy, surprisingly strong L = 0 transitions were observed to levels at 1831 keV, 1937 keV and 2053 keV, with strengths of 23%, 30% and 37% of that for the 5 2 +[642] bandhead. In 169Er, the 905 keV level was populated with an L = 0 transition that had 31% of the strength observed for the strong L = 0 transition to the 244 keV level. The nature of these states is at present not understood.

Fast light particle emission in 20 MeV/nucleon 20Ne induced reactions.

Energy spectra from nuclear reactions of $^{20}$Ne${+\mathrm{}}^{197}$Au at 20 MeV/nucleon were measured for charged particles with 1\ensuremath{\le}Z\ensuremath{\le}3 and 1\ensuremath{\le}A\ensuremath{\le}9. The detection angles covered a range from 5\ifmmode^\circ\else\textdegree\fi{} to 110\ifmmode^\circ\else\textdegree\fi{}. The data are analyzed in terms of moving source emission and a combined preequilibrium plus projectile breakup analysis. The preequilibrium calculations reproduce angle integrated cross sections and angular distributions of protons. They fail to reproduce angular distributions of complex particles. These distributions can be explained by the coalescence model employing the calculated pre- equilibrium cross sections for nucleons.

The 27Al(t, p) 29Al reaction at Et = 15 MeV

The 27Al(t, p) 29Al reaction was studied at an incident energy of E t = 15 MeV. Proton angular distributions were measured for the first 23 low-lying states. Comparisons of the data to DWBA calculations based on cluster-model and pure-configuration form factors were made which provided decompositions of the angular distributions into contributing L-values. Comparisons were also made to DWBA predictions based on microscopic amplitudes from a complete, sd-basis shell-model calculation.

Magnetospheric ions and electrons in the distant magnetosheath at ∼50 RE and ∼180 RE: ISEE‐3 observations

We have analyzed energetic electron (75 ‐ 115 keV) and proton ( ∼ 30 keV) measurements at the dawn side of the distant magnetosheath at ∼ 50 RE and ∼ 180 RE. The data have been obtained during the recent ISEE‐3 Geotail Mission. At ∼ 50 RE electrons and protons occur almost simultaneously in bursts of ∼ 2 min duration. The electrons stream intensely away from the general magnetopause position along the magnetic field line. The proton angular distributions exhibit a large parallel anisotropy that is symmetric with respect to the magnetic field in the plasma frame of reference. At ∼ 180 RE almost no electrons have been so far observed above the threshold of our detector. The protons are isotropic in the plasma frame. The observations are discussed in terms of a possible model where magnetosheath flux tubes are connected to the tail magnetic field so that the magnetospheric particles can leak out. At ∼ 50RE propagation to the spacecraft is believed to be scatter‐free; after reaching ˜ 200 RE the particles have resided long enough in the magnetosheath so that they are then coupled to the magnetosheath flow via pitch angle scattering.

Geometrical effect on the measurement of stopping powers: Angle-dependent energy loss of 7-MeV protons in Be, Al, Cu, Ag, and Ta

The geometrical effect on the measurement of stopping powers for 7-MeV protons, which was a hitherto-not-noticed effect until our previous experiment, has been studied more systematically with 7-MeV protons by changing the target thickness for Be, Al, Cu, Ag, and Ta. An improved experimental arrangement has been used to prevent the edge-scattered protons from affecting the energy-loss measurement. For all targets, the observed energy losses have been confirmed to increase with increasing emergence angle. It has also been found that this effect has a strong dependence on the thickness of the target. The dependence of this effect on the target atomic number cannot be judged properly from the present experiment. Angular distributions of protons due to multiple scattering agree fairly well with the predictions of Moli\`ere's theory. The comparison between our geometrical effect and the angular dependence of the energy loss observed for low-energy heavy ions has been discussed.

Photon polarization effects in photonuclear reactions

The 141Pr(γ, p 0) reaction induced by linearly polarized photons is investigated on the basis of the direct-semidirect model in the energy region of the dipole and quadrupole giant resonances. A detailed analysis of the differential cross sections and of the forward-backward asymmetries generated by the E1-E2 interference process in proton angular distributions is made by comparing the model results for unpolarized and polarized incident photons. The model predictions show that the emission probability, as well as the asymmetries with respect to 90°, is quite sensitive to the photon polarization state. By appropriately choosing the latter, investigation of the reaction mechanisms involved in the photonuclear process is favoured.

An experimental set-up for investigating fast neutron induced reactions

An eight-telescope system for measuring the energy and angular distribution of protons from the (n, p) reactions in the energy range 2.5–20 MeV is described. The proportional counters are used as d E/d X counters and Si(Li) detectors as E counters. Triple coincidences and two-dimensional analysis have been used. The construction of “multiwire” proportional counters is described. Time distributions between pulses from different counters and coincidence efficiency problem have been investigated. The system is tested using 19 MeV neutrons.

Systematics of the (t, p) reaction in Yb and Hf isotopes near the N = 108 "subshell closure"

Angular distributions of protons from the 170, 174, 176Yb(t, p)172, 176, 178Yb and 178,180Hf(t, p)180, 182Hf reactions have been studied using beams of 15 MeV tritons from the McMaster University tandem Van de Graaff accelerator. The reaction products were analyzed with a magnetic spectrograph and detected with photographic emulsions. Levels up to ~2.5 MeV excitation were studied in each nuclide, with a typical overall resolution of ~15 keV (full-width half-maximum). Measurements were also made with targets of natural Yb and natural Hf, to improve the accuracy of relative strengths in each chain of isotopes, and with a target of 172Yb to facilitate the normalization of previously published data to the present results. One of the most notable features of the data is the large amount of L = 0 strength to excited Iπ = 0+ states for all cases where the residual nucleus has a neutron number N ≤ 108. The populations of these states are not explained by either the pairing rotational or vibrational models. The SU(3) limit of the interacting boson model yields qualitative but not quantitative agreement. For two of the residual nuclides studied, 178Yb and 182Hf, there was little or no nuclear structure information previously available. The (t, p) experiments have located a number of excited states in each of these cases, and also give the first measurements of two-neutron separation energies; S(n) = 12 333 ± 6 keV for 178Yb and 12 413 ± 6 keV for 182Hf.

Possibility of prefusion emission from theC12+C12system

Angular distributions of protons from the /sup 12/C+ /sup 12/C reaction are discussed for low-spin states of the residual nucleus. It is suggested that the oscillating patterns observed experimentally could be explained assuming the emission of a proton from the strongly deformed /sup 12/C+ /sup 12/C system followed by fusion of the remaining nucleons.

Fluctuations due to statistical multistep compound emission in theMg25(He3,p) andMg25(He3,α) reactions

Excitation functions and angular distributions of protons and alpha particles emitted from the $^{3}\mathrm{He}$ + $^{25}\mathrm{Mg}$ reaction were measured in the $^{3}\mathrm{He}$ energy range from 8.05 to 20.425 MeV. The excitation functions show large, uncorrelated structures. Analysis on the basis of the autocorrelation function and the spectral density method yields largely varying values of the coherence energy, which can be attributed to the different steps of the statistical multistep compound emission chain. This process explains the average shape of the excitation functions, and also the absolute value of the emitted proton spectrum, measured at 13 MeV incident $^{3}\mathrm{He}$ beam.NUCLEAR REACTIONS $^{25}\mathrm{Mg}$ ($^{3}\mathrm{He}$, $p$), ($^{3}\mathrm{He}$, $\ensuremath{\alpha}$), $E=8.05\ensuremath{-}20.425$ MeV; measured $\ensuremath{\sigma}(E;\ensuremath{\theta})$; calculated $\ensuremath{\sigma}(E)$, $\ensuremath{\sigma}({E}_{p})$; deduced coherence widths.