E. Huttel

Screening corrections to the Rutherford cross section

Abstract Differential cross sections for elastic p-Au scattering were measured in the energy range between 0.2 and 0.8 MeV for scattering angles from 30° to 150° in order to determine corrections to the Rutherford cross section due to the screening of the nuclear charge by the atomic electrons. Furthermore, differential cross sections have been calculated in the weakly screening region using various screening functions. A simple analytical expression has been derived for the representation of both experimental and theoretical results.

Phase-shift analysis of pd elastic scattering below break-up threshold

Abstract A phase-shift analysis was performed for pd elastic scattering based on measurements of differential cross sections and proton and deuteron analyzing powers for energies below the break-up threshold. The angular momenta were restricted to l ⩽ 3; j -splitting and channel-spin mixing of the P-phases and the tensor coupling between the S- and D-phases were taken into account. The phase shifts were parameterized by the effective-range formalism and the corresponding parameters were directly deduced from the data. The results are compared with Faddeev calculations in which the Coulomb interaction is treated exactly or as a two-body approximation.

Proton stopping powers in various gases

Abstract The proton stopping powers of H2, He, N2, O2, Ne, Ar, Kr and Xe were measured for proton energies between 60 and 800 keV with an accuracy of about 2%. The protons were scattered off a thin gold foil mounted in the center of a gas-filled scattering chamber. The energy loss in the gas is given by the shift of the elastic peak measured with and without gas filling. The experimental data were fitted using the semi-empirical five-parameter formula of Andersen and Ziegler. Shell corrections were calculated from the measured stopping powers and compared to the theoretical shell-correction calculations of Bonderup which are based on the Lindhard-Scharff model.

Differential cross section, analyzing power and phase shifts for p-3He elastic scattering below 1.0 MeV☆

Abstract Differential cross sections and analyzing powers for the elastic scattering of polarized protons by unpolarized 3 He nuclei have been measured at eight energies between 0.3 MeV and 1.0 MeV for scattering angles θ c.m. = 52.4°–173.3°. The cross-section values were normalized to the Rutherford cross section for proton-krypton scattering. The analyzing powers have been measured with a statistical accuracy of about 0.001. The phase-shift analysis based on these data included all phases for orbital angular momenta l ≦ 1 and the channel-spin mixing parameter for the P waves. An energy parametrization of the phase shifts by an effective-range approximation allowed a simultaneous utilization of all data.

Differential cross sections and analyzing powers for pd elastic scattering below 1.0 MeV

Abstract Differential cross sections for the elastic pd scattering were measured at seven energies between 0.4 and 1.0 MeV for scattering angles from θc.m. = 44.5° to 149.2°. A mixture of D2 and Kr was used as target gas and the pd differential cross sections were determined relative to those of pKr scattering with a statistical error of Δσ σ ∼5 × 10−3. Analyzing powers for p d scattering were measured at 0.8, 0.9 and 1.0 MeV with a statistical error of ΔAy ∼5 × 10−4.

4He stopping cross sections in H2, He, N2, O2, Ne, Ar, Kr, e, CH4 and CO2

Abstract Helium stopping powers were measured for ten gases in the energy range between 0.1 and 1.1 MeV with a total accuracy of about 2.5%. Additionally, the proton stopping powers in CO 2 and CH 4 were determined. Optimum parameters for the Andersen-Ziegler semi-empirical formula were deduced for all data sets by means of the least-squares method. Stopping-power ratios S He / S p were determined using proton stopping powers for H 2 , N 2 , O 2 and the five inert gases which were measured recently with the same experimental set-up; they show a strong dependence on the target atomic number. The low-energy helium stopping cross sections were filted to the power function S = kE p . Experimental shell corrections were deduced from the measured helium stopping powers and compared with the theoretical shell corrections of Bonderup, whereby different higher-order Z l correction terms were included. The results show that in the energy range investigated it is not possible to obtain a consistent description for all gases.

Proton and helium stopping cross sections in Cl2 and Br2

Abstract Proton and 4He stopping powers for gaseous Cl2 and Br2 were measured in the energy ranges 50–750 keV and 100–1000 keV, respectively, and fitted with the semi-empirical Andersen-Ziegler formula. The peak energies are located near the minima of the oscillating structure as a function of the target atomic number Z2 recently observed by Gowda et al. The stopping-power ratios SHe/Sp for Cl2 and Br2 as a function of ion velocity show a similar behavior as for the adjacent inert gases Ar and Kr. The low-energy helium stopping cross sections were described by the power function S = kEρ, whereby ρ values of 0.5 for Cl2 and 0.67 for Br2 were found.

Proton and helium stopping cross sections in gaseous hydrocarbon compounds

Abstract Proton and 4He ion stopping powers were measured for various hydrocarbon gases in the energy ranges 60–750 keV and 100–1050 keV, respectively. The statistical and systematical errors are about 1% each. The target compounds, which contain different types of carbon-carbon bonds, were n-alkanes CnH2n+2(n = 1–10), 1-alkenes CnH2n(n = 2–4), 1-alkynes CnH2n−2 (n = 5–7), acetylene C2H2 and (l,3)-butadiene C4H6. Thus, this experiment provides a large data base for a Bragg-rule analysis with hydrocarbon compounds.

The Giessen polarization facility: III. Multi-detector analyzing system☆

Abstract Analyzing system with a PDP 11 computer and a digital multiplexer is described. It allows to accept signals from 16 detectors with individual ADCs simultaneously. For measurements of analyzing powers the polarization of the ion beam can be sw tched to zero with a frequency of 1 kHz. The switching operation additionally controls the handling of the detector pulses. The software contains special programs for the analysis of polarization experiments.

The polarized proton capture reaction 7Li(d, γ)8Be in the energy range from 380 to 960 keV☆

Abstract The polarized proton capture in 7 Li was used to study the reaction mechanism and to obtain spectroscopic information on the 8 Be nucleus. Gamma-ray angular distributions of the analyzing power were measured as a function of proton energy from E p = 380–960 keV with three Ge(Li) detectors simultaneously. The excitation functions of the cross section and the analyzing power are strongly energy dependent. The data were analyzed unambiguously and represented by three R -matrix elements, two M1 and one E1. The energy dependence of the two M1 matrix elements agrees with the well-known two 1 + resonances at E x = 17.642 and 18.157 MeV. The energy dependence of the E1 matrix element shows a smooth background presumably caused by a direct-capture mechanism, and furthermore, a resonant contribution, which is a significant suggestion of a new 1 − state in the 8 Be system at E x = 17.70 MeV with a width of Γ p = 180 keV.