Proton-Gamma-Winkelverteilungen an der Reaktion19F(p, α γ)16O

The angular distributions of the 6.13 MeV γ₁ transition in the reaction¹⁹F(p, α γ)¹⁶O have been measured with improved accuracy at proton energies of 873 keV and 1,374 keV using a Ge(Li) detector. The results can be fitted by Legendre polynom series witha ₂=?0,018±0.008;a ₄=0.000±0.008 atE _p =873 keV anda ₂=?0.130±0.005;a ₄=+0.004±0.004 atE _p =1,374 keV. From the measured Legendre coefficients α₁-angular momentum mixing ratios are extracted and compared with the results from (p, α₁) and (α₁, γ₁) correlations.     

Structures and decay of deep-hole states in light nuclei populated by the (p, 2p 2p) reactions

Decay particles from the s-hole states in ¹¹B and ¹⁵N have been measured in coincidence with the quasifree ¹²C(p, 2p) and ¹⁶O(p, 2p) reactions at E _p =392 MeV. Triton decay is found to be dominant for the ¹¹B(s-hole) state and also found to be larger than α decay for the ¹⁵N(s-hole) state despite its smaller Q value compared to α decay. Measured decay branching ratios are discussed in comparison with the results of statistical-model, SU(3)-model, and shell-model calculations. The energy spectra around the s-hole states in both ¹¹B and ¹⁵N exhibit some bumplike structures, which can be qualitatively explained by recent shell-model calculations for both nuclei.     

Structure studies of exotic nuclei using (<Emphasis Type="Italic">p</Emphasis>, <Emphasis Type="Italic">p</Emphasis>′) reactions

The structure of radioactive beams is investigated using the simplest possible probe: the proton used as a target in inverse kinematic reactions. From (p, p′) reactions, information on the neutron and proton transition densities is obtained through the comparison between the measured inelastic cross sections and the ones calculated using a microscopic potential and theoretical densities. (p, p′) inelastic scattering data to the first excited state for the halo nucleus ⁶He and for other nuclei ³⁴Ar and ^34,36S have been measured at GANIL using the MUST telescopes. This allows one to extract the global features of the transition densities, as shown for the halo nucleus ⁶He. We can also probe the evolution of the shell structure along isotopic chains in moving towards the neutron or proton drip lines. The example of the sulfur isotopic chain is discussed.     

12C(p,n)12N and 16O(p,n)16F reactions at Ep = 35 and 40 MeV: Reliability of the information obtained from DWBA analysis of low-energy (p,n) data

A high-resolution study of the ¹²C(p, n)¹²N and ¹⁶O(p, n)¹⁶F reactions was made at E_p = 35 and 40 MeV. The low-lying states in ¹²N(1⁺, 2⁺ and 2⁻) and in ¹⁶F(0⁻, 1⁻, 2⁻ and 3⁻) were clearly resolved, and their angular distributions were measured. Extensive DWBA analysis was made and compared with the data. The calculated angular distribution shapes are found to be in agreement with the data and insensitive to the choice of the parameters involved. On the other hand, the magnitudes of the DWBA cross sections depend strongly on the bound state parameters in the case of a transition from a tightly bound state to a loosley bound state. In the other cases the overall uncertainty of the DWBA cross section magnitudes was estimated to be about ±30%. Within this uncertainty the experimental cross sections for the ¹²C(p, n) reaction were explained by the calculation, but those for the ¹⁶O(p, n) reaction were not: the observed strengths were about a half of the calculated values. Since these results agree with those at intermediate energies, the origin of the discrepancy is considered to be in the structure of the mass 16 nuclei rather than in reaction dynamics. In general, the present results compare well with those at intermediate energies, indicating that the structure information extracted from low-energy, high-resolution (p, n) data is basically sound if careful analysis of the data is made.     

Investigation of two resonances in the18O(p,n)18F reaction

Excitation functions for the¹⁸O(p,n)¹⁸F reaction were measured at bombarding energiesE _p=4.6 to 6.6 MeV. In and near two resonances of the yield curves atE _p=5.622 and 6.061 MeV, angular distributions were measured with neutron time-of-flight techniques. The strong neutron decay to theT=1 state in¹⁸F and the similarity of the¹⁸O(p,n) and¹⁸O(n,n) yield curves give good evidence that the structures in the¹⁸O(p,n) yield curve arise from the formation ofT=3/2 states in¹⁹F. A two-level-analysis does not give satisfactory fits to the strongly asymmetric angular distributions.     

Experimentally determined transition probabilities of the systems 6p2→6p6d, 6p7s, 6p8s of neutral lead

Branching ratio measurements have been performed for all of the observed transitions from eight levels in neutral lead (6p²→6p6d, 6p²→ 6p7s, 6p²→6p8s) excited in a hollow cathode discharge in the 200–730 nm spectral range. From the relative emission intensity data, a set of absolute transition probabilities is derived for 28 lines, including lines for which transition probabilities have not been previously published. The absolute scales are obtained by averaging the measured lifetimes of the ³P⁰_1,2, ¹P_1⁰(6p7s), ³F^0_2,3, ³D^0_1,2(6p6d) levels.     

Inclusive ϱ0 production in γp interactions at 2.8, 4.7, and 9.3 GeV

Inclusive ?⁰ production in γp → ?⁰ + anything is studied at 2.8, 4.7, and 9.3 GeV, using the SLAC linearly polarized backscattered laser photon beam and the 82 inch hydrogen bubble chamber. Over this energy range the inclusive inelastic ?⁰ cross section rises from 6.0 μb to 20.5 μb. The multiplicity, i.e. the average number of μ⁰ mesons per inelastic hadronic event, has an energy dependence consistent with 1n s.The inclusive cross section is studied as a function of Feynman x, c.m. rapidity, and p_T² variables, and is also broken down into exclusive channels. At 9.3 GeV a forward inelastic peak is observed in the x distribution, containing mainly polarized ?⁰ mesons. The cross section for this inealastic diffractive component is 2.7 ± 0.6 μb. The p_T² distributions are exponential with a slope of 3 ? 4 (GeV/c)^?2, similar to that found in inclusive ?⁰ production in pp and μp reactions.     

An estimate of giant resonance effects in (α,p) transitions

A comparison of transition amplitudes for the¹⁶O(α, p)¹⁹F^* (1/2^?, 110keV) reaction suggests the utility of such reactions in the study of isoscalar giant resonances.     

Depolarization in proton inclusive inelastic scattering and in the (d,p) reaction on medium-weight nuclei

The energy-averaged depolarization parameter K_y^y′ has been measured for the inelastic scattering of 18 MeV protons from ⁵⁴Fe, ⁶³Cu and ⁹²Mo at 45°, 90° and 135°, and for 14.35 MeV protons from ⁶³Cu at 45° and 135°. In all cases K_y^y′ varies from approximately unity for scattering with low energy loss to approximately zero for inelastic scattering to high excitation energies. The change from one of these values to the other occurs over a region ≈ 6 MeV wide centered at about 5 MeV excitation. A simple two-component model fits both the K_y^y′ and inelastic crosssection data. K_y^y′ has also been measured for the ⁵⁴Fe($\text{d}$, $\text{p}$)Fe reaction with 16 MeV deuterons incident. Here K_y^y′ changes from approximately the maximum possible value, $\text{2}\text{3}$, to about zero in a 6 MeV region centered at roughly 13 MeV excitation. The ($\text{d}$,$\text{p}$) data can be fitted by an extension of the model used for the proton scattering data.     

The reactions 18O(p,p)18O and 18O(p,p')18O1(1.98 MeV) for Ep = 3.8–6.1 MeV

Angular distributions of cross sections and analyzing powers have been measured for ¹⁸O(p, p)¹⁸O and ¹⁸O(p, p₁)¹⁸O¹ (1.98 MeV) in 25 keV intervals for proton energies between 3.8 and 6.1 MeV. A phase-shift analysis of the elastic scattering data was carried out, yielding resonance parameters for 16 levels in ¹⁹F in the excitation energy region 11.6–13.8 MeV. The results generally are in good agreement with previous work. On the basis of spin, parity, excitation energy and a comparison of reduced proton widths with reduced neutron widths of levels in ¹⁹O, an assignment of $\text{T =}\text{3}\text{2}$ could be made to at least five of the levels, including the analog of the broad $\text{3}\text{2}{}^{\mathrm{+}}$ level in ¹⁹O at 5.45 MeV. A Legendre-polynomial analysis of the inelastic scattering data suggests that the cross section for proton energies between 5.0 and 5.5 MeV is dominated by the broad $\text{3}\text{2}$⁺ resonance at E_p = 5.15 MeV.     

Elastic and inelastic scattering of 800-MeV protons on <Superscript>16</Superscript>O and <Superscript>20</Superscript>Ne nuclei

Differential cross sections and polarization observables for the elastic and inelastic scattering of 800-MeV protons on ¹⁶O and ²⁰Ne nuclei are calculated on the basis of the theory of multiple diffractive scattering and the α-cluster model involving dispersion. The single-particle nucleon-density distributions obtained within the α-cluster model involving dispersion are used in the calculations. The differential cross sections and polarization calculated for elastic and inelastic p¹⁶O and p²⁰Ne scattering are compatible with available experimental data. The spin-rotation functions calculated for elastic p¹⁶O and p²⁰Ne scattering within the independent-nucleon model differ qualitatively from their counterparts calculated within the α-cluster model involving dispersion.     

Slow proton andΔ ++ production inK + p interactions at 70 GeV/c

The inclusive inelastic processesK ⁺ p→pX ⁺ andK ⁺ p→Δ ⁺⁺ X ⁰ are studied at an incident momentum of 70 GeV/c. The data comes from the Big European Bubble Chamber BEBC filled with hydrogen, exposed to an rf reparatedK ⁺ beam at the CERN SPS accelerator. The inclusive cross section for protons with laboratory momentump _LAB≦1.2 GeV/c is equal to (6.1±0.1) mb. InclusiveΔ ⁺⁺-production is studied for |t _{p, Δ}|<1.0(GeV/c)². Comparisons are made with otherK ⁺ p data and withpp data at 69 GeV/c. Evidence is found for Pomeron exchange at the beam vertex both for slow proton andΔ ⁺⁺-production as well as for absorptive pion exchange at the (p,Δ ⁺⁺) vertex.     

Determination of nuclear parameters by inelastic electron scattering at low-momentum transfer

The second-order Born-approximation treatment of Cutler and Schucan was applied to inelastic electron scattering data on ⁶Li, ⁶⁰Ni, and ¹¹⁴Cd acquired at low momentum transfers. The form factors as a function of momentum transfer q in the range of 0.25–0.57 fm^?1 were obtained by angular distribution measurements performed at incident energies of 30 to 60 MeV. The correlation between two parameters deduced from the measurements, the reduced transition probability B(E2↑) and the transition radius R⁽²⁾_tr, is discussed. It is suggested that inelastic electron scattering data at low-q is best used either in conjunction with an accurate value of B(EL↑) (available from the model-independent analysis of “photon” experiments at zero momentum transfer) to allow accurate determination of R⁽²⁾_tr, or in conjunction with high-q inelastic electron scattering data to allow accurate determination of B(EL↑) as well as R⁽²⁾_tr.     

Cluster Folding and Coupled-Channels Analysis of 16O + 16O Elastic and Inelastic Scattering

The data of elastic and inelastic ¹⁶O?+?¹⁶O scattering to the lowest 0⁺, 2⁺, and 3^? excitation channels of ¹⁶O in the energy range of 250–1,120 MeV is reanalyzed using the derived double folding cluster (DFC1) potential in the framework of the coupled-channels (CC) mechanism. The potential provides a very good agreement with the experimental data for the elastic and inelastic scattering angular distribution. Furthermore, the deduced deformation length and quadrupole and octupole deformation parameter are quite consistent with the corresponding electromagnetic measurements.     

Inelastic p 4He interaction in nonequilibrium cosmological nucleosynthesis

The current status of experimental data on inelastic p ⁴He scattering is reviewed, and the cross sections for respective channels are roughly estimated. These estimates make it possible to compute the amounts of ³He, ³H, and d nuclei produced in nonequilibrium cosmological nucleosynthesis to a precision of 10%. Investigation of inelastic p ⁴He scattering by using the method of accelerated ⁴He nuclei at E _p75 MeV is of particular interest for cosmological applications because this allows one to achieve a higher precision in calculating nonequilibrium cosmological nucleosynthesis.     

Effects of inelastic multistep processes on (p,t) reactions in a transition region between rare-earth nuclei and double-magic 208Pb

Effects of inelastic multistep processes on (p, t) reactions in a transition region between well-deformed rare-earth nuclei and the double-magic ²⁰⁸Pb have been investigated by the ¹⁸⁸Os(p, t) ¹⁸⁶0s, ^{194, 196}Pt(p, t)^{192, 194}Pt and ^{200, 202}Hg(p, t)^{198, 200}Hg reactions at E_p = 51.9 MeV. The observed ground 0⁺, first excited 2⁺ and 4⁺ angular distributions together with those for the ^{206, 208}pb(p, t)^{204, 206}pb reactions have been compared with CCBA and DWBA calculations, using transfer form factors based on the Nilsson, vibrational and shell models. It is found that the inelastic multistep processes play a very important role in reproducing both the shapes and magnitudes of the observed first excited 2⁺ angular distributions, contrasting to small contributions in the ground-state 0⁺ transitions. The effects of the inelastic multistep processes on the first excited 4⁺ transitions are also considered to be important.     

Selective excitation in kaon-nucleus inelastic scattering

The K⁺ meson (kaon) inelastic excitation of low-lying (E_x = 0–15 MeV) T = 0 collective states in ¹⁶O is theoretically studied as a function of energy and momentum transfer. The distorted wave impulse approximation is used to calculate angular distributions and total inelastic cross sections for exciting the first J^π = 2⁺, 3^?, 4⁺ and 5^? states at lab energies from threshold to 400 MeV. The distortions are represented in a Kisslinger-type optical potential constructed from elementary K⁺-nucleon amplitudes. Total nuclear elastic and reaction K⁺-nucleus cross sections are computed to demonstrate sensitivity to choice in K⁺-nucleon amplitudes. Fermi motion effects are also assessed using a simple averaging procedure. The weak absorption character of the kaon is reflected in the inelastic calculations which predict selective excitation of low spin states at low momentum transfer and high spin states at high momentum transfer.     

Medium corrections in intermediate-energy nucleon-nucleus scattering

Medium corrections in elastic and inelastic nucleon-nucleus scattering are discussed in the framework of Watson's multiple scattering theory. We derive formulae for the effective interactions to be used in the calculation of elastic and inelastic scattering based on a consistent local-density approximation. We show the numerical results of analyses of the p + ¹⁶O reaction at E_p = 135 MeV.