D. Kamke

Winkelverteilung und Wirkungsquerschnitt der Reaktion6Li(p, α)3He im Energiebereich von 50 bis 190 keV

In the angular distribution 1+A1 cos ϑ+A2cos2ϑ of the3He particles (cm. system)A1 decreases from +0.152±0.018 at 188 keV to −0.017±0.023 at 62 keV. The slope of the A1-curve is not approaching zero in this energy range, thereby showing the participation of terms of opposite parity even at very low energies. The total reaction cross section deviates from ans-wave Gamow-plot above appr. 130 keV, being 10 mb at 130 keV. The experimental results are discussed in connection with suggested level diagrams of the compound nucleus7Be.

Ghost anomaly and first excited state of 8Be in the 9Be(d, tα)4He reaction at 7 MeV

Abstract The three-body reaction 9 Be + d → t + α + α has been investigated in kinematically complete experiments at E d = 7.0 MeV for θ t = −40° and θ t = 40°, θ α = −72.5° to −162.5. The experimental spectra are dominated by sequential processes via intermediate excited states of 8 Be and 7 Li. R -matrix theory was employed to describe the line shape of the first excited state and the ghost anomaly of the ground state of 8 Be. Use was made of the αα phase shifts. The best fits were obtained assuming a channel radius of a αα = 4.5 fm. The average intensity of the ghost anomaly for E αα = 0.35–1.0 MeV is 4.3%/MeV ( θ t = 40°) and 8%/MeV ( θ t = 100°). For the first excited state of 8 Be we find E x = 3.00 MeV and Γ x = 1.23 MeV(FWHM).

Die Breite des 4+(11,4 MeV)-Zustandes von8Be aus7Li(d,n) 2α

With the reaction7Li+“d→n+8Be→n+2α the location and width of the8Be(4,+) level is redetermined. While the location at 11.4±0.05 MeV is found in agreement with known values, the width is found to be onlyΓ=2.8±0.2 MeV thereby disagreeing with data fromα-α-scattering but being close to a recent determination from the reaction10B(d,α)8Be (Γ=2.6 MeV). — No indication for participation of an excited state of5He in the simultaneously possible reaction via5He is found.ZusammenfassungDie Reaktion7Li+d→α+α+n verläuft für Deuteronenenergien zwischen 1 und 1,6 MeV und bei einem Winkel imSS zwischen den beidenα-Teilchen von 160° ausschließlich über den Zwischenkern8Be. Nach ausführlichen Ausgleichs- und Fehlerrechnungen ergab sich eine optimale Anpassung der Meßergebnisse mitEres=11,4 MeV undΓ=2,8 MeV als Daten des (4+)-Niveaus in8Be.Die statistischen Fehler betragenΔEres=±0,05 MeV undΔΓ=±0,2 MeV.Die ermittelte HalbwertsbreiteΓ liegt unter dem ausα-α-Streudaten ermittelten Wert Гαα.Eine systematische Abweichung der HalbwertsbreiteΓ von Гαα wurde bereits für das (2+)-Niveau in8Be beobachtet 22. Man schloß daraus, daß die Anwesenheit des dritten Teilchens die Lebensdauer des8BeKerns verlängert.

Analyzing power of the 2H(n, np)n breakup reaction at 67 MeV in selected kinematical configurations

Abstract The angular distribution of the analyzing power A y for the 2 H( n , np)n breakup reaction at 67 MeV was measured in two kinematical regions: np quasi-free scattering and np final-state interaction. The results are compared with rigorous three-nucleon calculations using the Paris potential and allowing for charge dependence in the 1 S 0 state. According to the actual experimental conditions energy averaging was simulated in the theoretical calculations. In both configurations agreement between experimental and calculated values is found.

Energy spectrum and angular distribution of the α-particles of the reaction 11B (p, α)8 Be=(2,9 MeV) in the vicinity of the 163-keV resonance. Part 1.

The energy spectrum consists of a broad line (0·8 MeV) at 3·88 MeV and a continuum from 0·05 to 4·9 MeV. The shape of the continuum depends on the angular distributions of the decays taking part in the reaction. The energy spectrum was measured under 90° with respect to the proton beam (CsJ+Photomultiplier and amplitude discriminator), it shows anisotropies of the α-emissions with strong interference in the 163 keV resonance.

Winkelverteilung und Energiespektrum der α-Teilchen der Reaktion11B (p, α)8Be= (2,9 MeV) in der Umgebung der 163 keV-Resonanz. II

Calculations and discussion of the energy spectrum and of the angular distribution of the α-particles for a measurement of the energy spectrum under 90° with respect to the proton beam.

Facility for neutron induced few body reactions at Bochum University

Abstract A facility is described which is designed for the measurement of neutron induced three-body breakup. It has been used for the breakup of deuterium and of the nucleus 9 Be. Neutrons are produced by a pulsed beam of deuterons from the Bochum 4MV Dynamitron-Tandem accelerator by bombarding a thick tritium-titanium target or a deuterium gas target. The outgoing beam is collimated by a 4π shielding to a solid angle of about 1 msr. In most cases, a liquid scintillator (NE232 or a mixture of NE232/NE213) serves as a target for the neutron beam. Scattered neutrons are detected by NE213-detectors of different sizes. For testing purposes the differential elastic n-d cross section and simultaneously the response of NE232 have been measured at 22.4 and 7.9 MeV.

Experimente zum Ablauf der Kernreaktion11B(p, 3α) in der 675 keV-Resonanz

In continuation of measurements at very low energies1,2 the correlation in angle and energy of two of the emittedα-particles has been measured with standard coincidence technique at a proton energy of 675 keV (2−, level in12C at 16.57 MeV) by placing two surface-barrier-detectors in the plane perpendicular to the beam. The results are displayed in a Dalitz-diagramm, the pertinent formulae for conversion of laboratory system to c.m. system are given. The distribution of points in this plot shows that the decay from the reached level in12C proceeds only by sequential decay3. This confirms earlier results found at very low energies (130 keV and 250 keV) but differs from those found at a proton energy of 163 keV (2+, level in12C at 16.11 MeV).

Die Winkelverteilung der Protonen der Reaktion B11 (d,p0,1 B12 im Energiebereich von 0,7 ... 1,7 MeV

Angular distributions of the protons in this low-energy region have been measured by only few groups for obvious reasons: the energy of the emitted protons is very low. It will be shown that by using non-supported targets of B11 with very little oxygen contamination the angular distributions can be obtained between approximately 5 and 165 degrees (cm.,p0-group) and between 20 and 165 degrees (cm.,p1) with high accuracy. The Butler-fits givel=1,rB=5.2 fm forp0 andl=1,rB=4.7 fm forp1. All angular distributions seem to exhibit strong participation of non-stripping mechanism.

Neutron-neutron scattering length in the reaction9Be (n, nn)8Be at 10.3 MeV

In a kinematically complete experiment on9Be(n, nn)8Begs at 10.3 MeV, the absolute differential cross section of then-n FSI configuration at Θlab=30° has been measured. It was our particular object to determine the singlet scattering length of then-n interaction via its final-state interaction being embedded in a multi-nucleon background. An extended and thorough analysis yielded1ann=−16.5±1.0 fm which is consistent with the results of the most recent and most precise kinematically complete measurements with three hadrons in the final state. These, however, altogether contradict the values deduced from π−d→nnγ.