Electron scattering studies of low-lying collective states of even Zn isotopes

The inelastic electron scattering cross sections for the excitation of the low-lying collective states in the even Zn isotopes ⁶⁴Zn, ⁶⁶Zn, ⁶⁸Zn and ⁷⁰Zn have been measured in the momentum transfer region q = 0.3–1.1 fm^?1. Strong transitions to the first 2⁺ and 3^? states have been observed and the modified Tassie model with a two parameter Fermi charge distribution for the ground state was used to extract the values for the reduced transition probability B↑ (Eλ). Besides the investigation of these states, which in the framework of the vibrational model are considered as one-phonon states, special effort was made to measure the transition to the 2⁺ two-phonon states in ⁶⁴Zn (ε = 1.80 MeV) and ⁷⁰Zn (ε = 1.76 MeV). We have applied the anharmonic vibrator model to these two nuclei and have extracted values for the static quadrupole moment of the first excited state.     

Electron scattering from 70Ge and 72Ge

Cross sections have been measured for the elastic and inelastic scattering of electrons from ⁷⁰Ge and ⁷²Ge for momentum transfers from 0.65 to 1.14 fm^?1. Values for the parameters of a Fermi type ground-state charge distribution were obtained from a phase shift analysis of the elastic cross sections. The rms charge radius corresponding to these parameters is 4.07±0.02 fm for ⁷⁰Ge and 4.05±0.03 fm for ⁷²Ge. Using DWBA analysis the reduced transition probabilities for the electroexcitation of the 2₁⁺ and 3₁^? states were found to be: B(E2, ω)↑ = 19.7±1.2, 26.8±2.0 W.u.; B(E3, ω)↑ = 36±5, 37±7 W.u. for ⁷⁰Ge and ⁷²Ge respectively. The J^π = 3^? assignments for the state at 2.562 MeV in ⁷⁰Ge and 2.515 MeV in ⁷²Ge are confirmed.     

Excitation of the quasi-bound state in 4He by electron scattering at medium momentum transfer

The cross sections of inelastic electron scattering on ⁴He leading to the quasi-bound state (0⁺, ε = 20.1 MeV) were measured in the momentum transfer range 0.8 fm^?2 < q² < 2.4 fm^?2. We found it to be a pure longitudinal transition and give the form factor of this C0transition.     

Untersuchung der beiden ersten angeregten Zustände des Li6-Kernes durch Elektronenstreuung

Inelastic electron cross sections for Li⁶ were measured using the facilities at the 300 MeV linear accelerator of the Institut für Kernphysik in Mainz. The form factor for theC 2 transition to the 2.184 MeV level is given in the region of momentum transfer 0.4 fm^?1<q<1.9 fm^?1. It was possible to determine the form factor for the 3.562 MeVM 1 transition up toq=1.2 fm^?1.     

ππ production by ee annihilation in the ϱ energy range with the Orsay storage ring

A large solid angle detector has been used to observe two body events produced by electron-positron collisions in the Orsay storage ring. From the π⁺π⁻ excitation curve in the ? region we have deduced the amplitude and the phase of the ω-? interference, and the ? resonance paramaters: M_? = (775.4±7.3) MeV, Γ_? = (149.6 ± 23.2) MeV, √B(ω→π⁺π⁻) = 0.19 ± 0.05, φ = (85.7 ± 15.3)⁰, σ(e⁺e⁻→?) = (1.00 ± 0.13) μb at S = M_?², B(?→e⁺e⁻ = (4.1 ± 0.5) × 10⁻⁵, Γ(?→e⁺e⁻) = (6.1 ± 0.7) keV, (g_?²/4π) = 2.26 ± 0.25, (g_?ππ²/4π) = 2.84 ± 0.50.     

Electron scattering studies of magnetic isovector transitions in 12C at high momentum transfer

The inelastic electron scattering cross sections for the M1 transition to the 15.11 MeV (1⁺, T = 1) level and for the M2 transition to the 16.58 MeV (2^?, T = 1) level in ¹²C have been measured in the momentum transfer region q = 0.4–3.0 fm^?1, with emphasis on precise data at high momentum transfers. Additionally, a broad state near 15.4 MeV excitation has been observed and its excitation energy and natural width have been established as 15.44 ± 0.04 MeV and 1.5 ± 0.2 MeV, respectively. The Fourier-Bessel technique for determining the Mλ transition current density has been applied to the M1 and M2 transitions. Particular attention has been paid to the Coulomb corrections required to deduce the PWBA form factors. The M1 radiative width is Γ_γ0 = 38.5 ± 0.8 eV.     

Study of low-lying levels in 47Ca with the 48Ca(d, t)47Ca reaction

Angular distributions of cross sections [α(θ)] and vector analyzing powers [iT₁₁(γ)] have been measured for seven low-lying states or groups of states excited by the ⁴⁸Ca($\text{d}$, t)⁴⁷Ca reaction with 13.5 MeV deuterons and analyzed by the DWBA. On the basis of comparison of vector analyzing powers with DWBA calculations, spin-parity assignments have been made or confirmed for several states. Spectroscopic factors have been extracted. Angular distributions for weak states at 3.30 and 3.57 MeV excitation in ⁴⁷Ca could not be reproduced by DWBA calculations. Investigations of compound nucleus and multi-step contributions to the cross sections and analyzing powers for these states have been made by means of Hauser-Feshbach and CCBA calculations. Optical model parameters were obtained from analysis of 13.5 MeV deuteron elastic scattering cross sections and analyzing powers.     

Optical-model analysis of the elastic scattering of 100 MeV protons from Mg and Si

Elastic scattering differential cross sections for the interaction of 100 MeV protons with ²⁴Mg and ²⁸Si have been measured using a high-resolution Ge(Li) spectrometer to resolve the inelastic scattering contribution to the elastic peak. The results have been analysed using the conventional optical model, and the experimental differential cross sections and total reaction cross section are excellently reproduced. The results agree with previous analyses of the elastic scattering of 100 MeV protons on 1p shell nuclei in that no set of geometric parameters can provide a quantitative fit to both nuclei. It is observed, however, that the fluctuations of the optical-model parameters for optimum fits are decreased over the fluctuations observed for the 1p shell nuclei. The present results combined with previous optical-model analyses on ²⁴Mg and ²⁸Si at 50 MeV and 40 MeV respectively, are found to be consistent with an energy dependence of dV/dE ≈ −0.3 for the depth of the real central potential in agreement with other, more extensive, investigations of the energy dependence for protons elastically scattered from ¹⁶O and ⁴⁰Ca.     

Nuclear structure effects in sub-barrier fusion cross sections

The total fusion cross sections around and down to ≈ 12 MeV below the Coulomb barrier in the c.m. system have been measured with the Munich heavy-ion recoil spectrometer for 30 projectile-target combinations: ^{32, 36}S + ^{92, 94, 96, 98, 100}Mo, ^{100, 101, 102, 104}Ru, ¹⁰³Rh, ^{104, 105, 106, 108, 110}Pd, The excitation functions can be reproduced with a one-dimensional barrier penetration model by increasing the nuclear radii by $\text{ΔR ? 0.255 ± 0.035}\text{fm}$ and introducing a gaussian distribution of the nuclear radius R with a standard deviation σ_fit(R). The σ_fit(R) can be explained as being due to quadrupole vibrational fluctuations of the surface-to-surface distance at the barrier and to two-neutron-transfer reactions with positive Q-values.     

Investigation of the Li (e,e′p) reaction at 1200 MeV

The reaction ⁶Li (e, e′p)⁵He has been investigated with a resolution good enough to distinguish the effects of the s- and p-shells of the ⁶Li nucleus. The reaction cross section has been measured as a function of the missing energy from −15 to +30 MeV. The proton angular distribution has been measured at missing energies of 4 and 20 MeV. The comparison of the data with calculations within the framework of the plane-wave impulse approximation gives the harmonic oscillator parameters q_p = 50 ± 5 MeV/c,q_s = 108 ± 9 MeV/c.     

The B(E2) for the first 2 state in Zr

A model-independent measurement of the width of the first 2⁺ state (2.186 MeV) of ⁹⁰Zr has been carried out using the resonant scattering of bremsstrahlung and its detection with a Ge(Li) detector. The observed resonance fluorescence yield corresponds to a reduced E2 transition probability B(E2↑) = 608 ± 35 e² · fm⁴. The difference between this value and recent inelastic electron scattering results exceeds the range usually attributed to the model dependence of the latter.     

Properties of the φ and f′ produced in the channel Kp → KpKK̄ at 10 GeV/c

Data are presented and cross sections given for ф and f′ production in the channel K⁺p → K⁺pKK? at 10 Gev/c. The resonance parameters obtained from a fit to the KK? effective mass distribution are M = (1020.4 ± 0.5) MeV/c² and Γ = (5.0 ± 1.3) MeV/c² for the ф meson and M = (1514 ± 4) MeV/c² and Γ = (28 ± 15) MeV/c² for the f′. The resonance widths are corrected for experimental resolution. The branching fraction for the rate (ф → K⁰₁K⁰₂)/(ф → K⁺K⁻) is determined to be 1.15 ± 0.15. The angular distributions for the decay of the f′ have unnormalized moments _H(2,0) and H(4,0) different from the values for the nearby background, indicating spin 2 or greater for the f′.     

Scattemng of 14.1 MeV neutrons from 209Bi

Differential cross sections for the elastic and inelastic scattering of 14.1 MeV neutrons from ²⁰⁹Bi have been measured with a time-of-flight system which had an energy resolution of 650 keV. For elastic scattering from ²⁰⁹Bi, an optical-model analysis gave the best-fit potential parameters. The absolute cross sections for excitation of collective (2.66 and 4.36 MeV) states are reproduced by the results of distorted-wave calculations under the assumption of a core (²⁰⁸Pb) excitation model using deformation parameters obtained from (p, p') reactions.     

Beta-delayed proton emitter kr

The nucleide ⁷³Kr has been identified by on-line mass separation as a precursor of β-delayed proton emission. The proton branch is (6.8 ±1.2) × 10⁻³ proton/decay. The protons populate the ground state and also the first excited 2⁺ state at 866 keV in ⁷²Se with a relative intensity of (35±9) %. The value of Q_EC−B_p, where B_p is the proton separation energy for the nucleus ⁷³Br, is found to be 4.85 ±0.30 MeV based on the fraction of proton events preceded by positron decay.     

Anregung des 7,66 MeV-Niveaus in Kohlenstoff-12 durch unelastische Elektronenstreuung

Using the facilities of the Darmstadt electron linear accelerator the cross section for the excitation of the 7.66 MeV level in Carbon-12 was measured for momentum transfers between 0.25 and 0.55 fm^?1. Extrapolation of the measured cross sections for vanishing momentum transfer yields a partial width for the decay to the ground state through internal pair production of (7.3±1.3)·10^?5 eV. The dependence of the reduced transition probability on momentum transfer is discussed and compared with theoretical predictions.     

Measurement of K production in the reaction Kp → Kp

The K^∗− spectrum in the reaction K⁻+p → K^∗−+p has been measured at beam momenta 10.9, 13.4 and 15.9 GeV/c using the missing mass technique. Production of the L(1770), and a Q-K^∗(1420) enhancement are observed. Differential cross sections in the range of momentum transfer 0.12 < | t_pp | < 0.40 (GeV/c)² are given. The L meson is observed with a width Γ = 100 ± 26 MeV. The mass spectrum between the L and 2.5 GeV does not show significant structure.     

Interaction of slow neutrons with natural Rutenium,Rhodium, Cadmium and Thallium and some of their isotopes

By means of Christiansen filter technique the following bound coherent neutron scattering lengths were obtained:^natRu:b=7.02 ± 0.02 fm¹⁰⁸Cd:b=5.31 ± 0.24 fm¹⁰³Rh:b=5.90 ± 0.04 fm¹¹⁰Cd:b=5.78 ± 0.08 fm^natTl:b=8.773 ± 0.015 fm¹¹¹Cd:b=6.47 ± 0.08 fm²⁰³Tl:b=8.51 ± 0.08 fm¹¹²Cd:b=6.34 ± 0.06 fm²⁰⁵Tl:b=8.87 ± 0.07 fm¹¹⁴Cd:b=7.48 ± 0.05 fm¹¹⁶Cd:b=6.26 ± 0.09 fm In combination with some total cross section measurements with neutrons in the eV-energy range and with the compiled resonance parameters we deduced consistent sets of spin state scattering lengths and potential radii.     

Investigation of the φ-meson resonance by electron-positron colliding beams

Using the colliding beam machine, VEPP-2, the excitation curve of the ø-meson resonance was investigated in the three main decay modes. The resonance parameters obtained are the width, the total cross-section and the branching ratios. Namely: Γ = (4.67 ± 0.42) MevB(K⁺K⁻) = (54.0 ± 3,4) %σ_o = (3.96 ± 0.35) μBB(K^o_sK^O_L) = (25.7 ±3,0) %B(e⁺e⁻ = (2,81 ± 0.25) × 10⁻⁴B(π⁺π⁻π^o) = (20.3 ± 4,2) %     

Energy levels of O between 10.0 and 17.1 MeV excitation

A phase-shift analysis has been performed on ¹²C(α, α₀)¹²C cross sections which were measured over a broad angular range from 4.0 to 13.3 MeV in 15 to 50 keV increments. In addition to confirming the presence and determining the J, π, Γ, Γ_α, of the levels at 10.36, 11.50, 11.60, 12.47, 13.10, 13.11, 13.13, 13.25, 13.89, 14.07, 14.6, 14.82, 14.87, 15.47 and 16.30 MeV excitation in the ¹⁶O compound system, the results include the observation of a new 0⁺ level at 15.17 MeV. Definite J^π values of 4⁺, 5⁻ and 3⁻ have been assigned for the levels at 14.6, 14.82 and 15.47 MeV respectively. Refined level parameters are given for the 0⁺ (14.07 MeV) and 6⁺ (14.87 MeV) levels.     

The 6Li(e,e′α) and 6Li(e,e′d) reactions at 520 MeV

The reactions ⁶Li(e,e′α) and ⁶Li(e,e′d) have been studied at T₀ ≈ 520 MeV and q ≈ 1.4 fm^?1, by coincidence measurements. The angular dependence of the cross sections is interpreted in the plane wave impulse approximation to obtain the momentum distribution of α-particle and deuteron clusters in ⁶Li. The amount of clustering of ⁶Li is also discussed.