Preequilibrium α-emission in the Au(p,αx)-reaction at Ep = 72 MeV

Proton-induced α-spectra from ¹⁹⁷Au have been measured at E_p = 72.3 MeV and the angle-integrated cross section is compared to an exciton model Monte-Carlo calculation and to the spectral distribution of α-particles emitted after the absorption of negative pions at rest.     

The break-up reaction p0 + d → p1 + p2+ n at E0 = 16 MeV

The break-up reaction p₀ + d → p₁ + p₂ + n has been studied at E₀ = 16 MeV in kinematically complete p₁-p₂ coincidence experiments with special regard to n-p final-state interactions (f.s.i.) and p₁-p₂ quasifree scattering (q.f.s.). The absolute differential cross section has been measured for n-p f.s.i. c.m. production angles from 60° to 140° and for four pairs of angles with strong contributions due to q.f.s. Calculations with separable nucleon-nucleon potentials based on the Faddeev equations are in good agreement with the data obtained. In general, the shape of the experimental differential cross section is well reproduced. Discrepancies of up to 30 % in the worst cases arise between the absolute values of the theoretical predictions and the experimental data.     

nn Scattering parameters ann and rnn from the photon spectrum of the reaction πd → γnn

A high-statistics measurement of the photon spectrum of the reaction π⁻d → γnn has been performed. The comparison of this spectrum with theoretical spectra folded with the response curve of the spectrometer (measured by the reaction π⁻p → γn) has provided precise values of the neutron-neutron scattering length, a_nn = −18.5 ± 0.4 fm, and of the effective range, r_nn = 2.80 ± 0.11 fm. Theoretical uncertainties of 0.20 fm and 0.11 fm, respectively, have been evaluated.     

The 2H(p, 2p)n reaction at Einc = 45 MeV and its sensitivity to various separable S-wave N-N potentials

This paper presents and analyses the data for the ²H(p, pp)n reaction at E_inc = 44.9 MeV. Kinematic conditions including the quasi-free scattering region and the regions far from quasi-two-body processes are considered. The experimental results are compared with the predictions of several separable S-wave models of the N-N interaction. Potential models that differ only off-shell, as well as models that predict different N-N scattering results are included to help to isolate aspects of the break-up reaction sensitive to off-shell and on-shell differences. The regions far from quasi-free scattering are generally much more sensitive to the off-shell features of the interaction than are quasi-free scattering results. On-shell differences in the potential affect predictions in all regions of phase space with the potentials best representing the free N-N data giving the best overall fit to the data over most regions of phase space.     

The reaction mechanism of the 7Li(n,tα)n reaction at En = 14.4 MeV

The correlation spectra of the three-body break-up of the n+⁷Li system have been studied at a neutron energy of 14.4 MeV. The analysis of the data reveals the predominant role of sequential processes. The Phillips-Griffy-Biedenharn theory has been applied to fit the data. The contribution of quasi-free scattering has also been observed and analysed in the frame of the PWIA.     

3H(p,n)3He reaction with polarized protons from threshold to 2.9 MeV

A polarized beam was used to measure angular distributions of the analyzing power of the ³H($\text{p}$, n)³He reaction at 9 energies from 1.30 to 2.90 MeV. The data were measured typically to an accuracy of 0.02 with a target 25 keV thick at 2 MeV bombarding energy. The analyzing power can be fitted with associated Legendre polynomials. The coefficient of P₁¹ is small, near zero at the upper and lower energies and negative in between; the coefficient of P₂¹ is much larger and positive, rising to a maximum at 2.2 MeV. Comparison of the analyzing power A with earlier data for the neutron polarization P induced with unpolarized protons shows the coefficients of P₁¹ to be equal and those of P₂¹ to have a similar energy dependence but with larger values for A than for P. Theoretical treatment elsewhere of the inequality of P and A infers that transitions between ³P₂ and ³F₂ are responsible. Polarization contour maps are given.     

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.     

Excitation of ΔL = 1 resonances in the (p,n) reaction on Zr, Sn, Ce and Pb at Ep = 41 MeV

A broad peak was systematically observed at about 10 MeV above the Gamow-Teller resonance in the ⁹⁰Zr, ¹²⁰Sn, ¹⁴⁰Ce, ²⁰⁸Pb (p,n) reactions at E_p = 41 MeV. The angular distribution shapes of these peaks support the interpretation that they they correspond to ΔL = 1 state. The data are compared with TDA-DWBA calculations.     

The tensor analyzing power Azz AT θ = 0° for the He( , p)He reaction

The tensor analyzing power f_zz has been measured for the ³He( , p)⁴He reaction at 0 = 0° over an incident deuteron energy range E_d = 6.6–15.8 MeV in steps of 0.5 MeV. The present results agree with and extend the previous measurements of Grüebler et al. The present results indicate that this reaction is a very good tensor analyzer for polarized deuteron beams with energies up to 15.8 MeV.     

207Pb(p,p') measurements at 135 and 61 MeV,the effective interaction and core polarization

Data at Einp = 61 and 135 MeV for neutron-hole transitions are used to study the proton-neutron part of the assumed NN force. Collective core-polarization strengths (A_L) from the present fits at 135 MeV are consistent with those extracted from the (e, e') reaction for two L = 2 transitions and one L = 4 transition. This is not the case at 61 MeV where the A_L values needed to fit the (p, p') data are much smaller for transitions to the $\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{and}\text{f}{}_{\mathrm{<mtext>7</mtext><mtext>2</mtext>}}$ hole states. A fully microscopic DWBA fit is successful for the L = 3 transition to the doublet at 2.64 MeV of excitation at E_p = 61 MeV, but fails at 135 MeV; a fully microscopic DWIA calculation provides a reasonable fit to the data at 135 MeV.     

Energy levels of K from Ar(p, p)Ar and Ar(p, p′γ)Ar

The elastic and inelastic scattering of protons from ³⁶Ar has been investigated from 2.1 to 5.3 MeV using a gas target. Experimental energy resolution varied from 11 keV to 5 keV over this range. The results are interpreted in terms of 56 states in ³⁷K between the energies of 4.0 and 7.0 MeV excitation with the aid of single-level dispersion theory. The width and spin and parity or proton l-value are determined for the 38 states seen in the elastic scattering. Upper limits are placed on the total widths of levels seen only in the inelastic scattering.     

The 52Cr(t,p)54 reaction at Et = 15 MeV

Using the ⁵²Cr(t, p)⁵⁴Cr reaction at a bombarding energy of 15 MeV, excitation energies have been measured for 30 levels up to E_x = 5.583 MeV in ⁵⁴Cr. Angular distributions were obtained for all but one of these levels; these have been compared with distorted-wave Born approximation (DWBA) calculations to determine the L-transfer (and hence J^π). The measured cross sections have been compared to the predictions of DWBA calculations that use two-neutron transfer amplitudes from a shell-model calculation with the active neutrons restricted to the $\text{(2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{,}\text{If}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{, 2}\text{p}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{)}$ orbitals.     

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.     

Elastic scattering of deuterons by 14C from Ed = 4 to 10 MeV

Angular distributions for the elastic scattering of deuterons by ¹⁴C were measured at nine energies between E_d = 4.2 and 10 MeV. Excitation functions were taken in 50 keV steps from E_d = 4 to 10 MeV. A resonance was observed at E_d = 4.5 MeV, which corresponds to an excitation energy of 14.41 MeV in ¹⁶N. An analysis using an optical model plus a single-level formula derived from the R-matrix formalism yields an l-value assignment of l = 4 for this resonance. Of the three J^π values allowed for l = 4 (J^π = 3⁺, 4⁺, 5⁺), the value of J_π = 3⁺ is found to be slightly preferred. Possible identification of this resonance with an analog in ¹⁶O is discussed. The angular distributions measured at off-resonance energies were analyzed with an optical-model potential which has a surface-peaked imaginary well. The energy dependence of the real and imaginary well depths are explicitly determined in the present work for E_d = 4 to 10 MeV. The best-fit optical-model parameters obtained from the present study are compared to those from the ¹⁴N(d, d)¹⁴N work.     

The c(d,n0)n reaction from 3.6 MeV to 12.0 MeV

The excitation function for the reaction ¹²C(d, n₀)¹³N was measured at 0° in the energy range of 3.6 to 12.0 MeV deuteron bombarding energy. Angular distributions were measured at 7.0, 8.0, 9.0, 10.5 and 12.0 MeV deuteron bombarding energies. Cross sections are compared with the ¹²C(d, p₀)¹³C reaction. The yield curves for the neutron and proton groups show a strong similarity in shape. Different sets of deuteron and proton optical-model parameters were used in fitting the 8 MeV energy averaged angular distribution.     

The (p,t) reaction on 12C, 54Fe and 208Pb at 80 MeV

Angular distributions have been measured for the low-lying levels of the residual nuclei for the ¹²C, ⁵⁴Fe and ²⁰⁸Pb(p, t) reactions at E_p = 80 MeV. The shapes of these angular distributions are generally well reproduced by the zero-range distorted-wave Born approximation (DWBA). Enhancement factors extracted from the data show that the DWBA predicts relative strengths consistent with those observed at lower bombarding energies. However, the overall empirical DWBA normalization at E_p = 80 MeV is observed to be $\text{1}\text{12}$ ($\text{1}\text{4}$) of that required at 40 MeV for ²⁰⁸Pb (⁵⁴Fe).     

Coplanar and noncoplanar experiments on the reaction H(d,pp)n at Ed = 12.9 MeV

Coplanar and noncoplanar differential cross sections of the reaction H(d, pp)n were measured in kinematically complete experiments. The two-dimensional spectra were accumulated off-line in an alternative way, which enabled us to eliminate the distortion due to the finite geometry. The data were compared with the charge-dependent Ebenhöh code using two S-wave rank-one separable potentials. The theory predicts the shape of the cross sections reasonably well. Deviations of 20 % occur in the absolute scale especially in the final state region. Codes that account approximately for the Coulomb interaction fit the data better only in the region with low relative p-p energy.     

Polarization of protons from the Be(d,p)Be reaction at Ed = 12.0 MeV

The polarization of protons from the ⁹Be(d,p)¹⁰Be reaction at E_d = 12.0 MeV was measured for the ground state and first excited state transitions. The results obtained are compared with the predictions of DWBA theory. It was found that better fits to the experimental data can be obtained using volume absorption in the distorting potential of the deuteron elastic channel. A comparison of the present polarization data with the vector analysing power for the same reaction and the same incident deuteron energy has also been made.