Subpicosecond lifetimes of high spin states in the rotational nuclei 73Se, 74Se and 74Br have been measured using the 58Ni +19F compound reaction and the Doppler Shift Attenuation method. Six EUROBALL Cluster detectors arranged in cube geometry allowed us to select the relevant transitions in γγ coincidence mode. The high counting statistics achieved in this setup also facilitated the determination of average sidefeeding times, which were found to agree rather well with the results of Monte-Carlo calculations of the particle and γ-ray evaporation process. The deduced quadrupole strengths and deformations are compared with the results of previous measurements and the predictions of Cranked Shell Model calculations. In 74Br, a large and constant prolate deformation of β2= 0.37(1) was found for the presumed 4+ and 3− two-quasiparticle bands.

The γ-ray spectrum of252Cf(sf) was measured in the Darmstadt-Heidelberg Crystal Ball spectrometer, with a double ionization chamber mounted inside to detect the fission fragments. The measurement was aimed at a better understanding of an unusual component found in the high-energy region between 3 and 8 MeV, with fragment mass splits near symmetry. This component was proved to be predominantly emitted by the heavier fragment, to reach its highest intensity at a fragment mass split of 132:120, and to have an almost isotropic angular distribution. Calculations with the statistical code CASCADE could reproduce the main features.

Aγ-γ coincidence technique has been developed forg-factor measurements of short-lived nuclear states. The method involvesγ-detection in 4π geometry as well as transient magnetic fields and the recoil-distance technique. A first experiment was performed for the isotope160Yb produced in the reaction64Ni(100Mo, 4n) at 430 MeV beam energy. The valueg=− 0.23(31) of the 14+ yrast state, which is compatible with zero, establishes thevi13/2 quasiparticle structure to be responsible for the first backbend. A meang-factor for low spin states around the 4+ state,g=+0.48(26) was also derived as well as lifetimes for yrast states up toIπ=8+.

A rotational band with states of alternating parity has been populated in224Th via the208Pb(18O, 2n) reaction. Spins up to Iπ=10>+ (11−) are identified. Stretched El and E2 transitions compete in the deexcitation, the average ratio of the reduced transition probabilities being B(E1)/B(E2)=(1.5±0.4)×10−6 fm−2. This ratio implies that224Th has one of the largest intrinsic electric dipole moments observed so far.

A rotational band with states of alternating parity has been populated in224Th via the208Pb(18O, 2n) reaction. Spins up to Iπ=10>+ (11−) are identified. Stretched El and E2 transitions compete in the deexcitation, the average ratio of the reduced transition probabilities being B(E1)/B(E2)=(1.5±0.4)×10−6 fm−2. This ratio implies that224Th has one of the largest intrinsic electric dipole moments observed so far. The low-lying odd-parity excitations in the neutron deficient even Ra and Th isotopes have long been our main evidence for the occurrence of octupole deformations in nuclei at the beginning of the actinide region. More recently, new evidence for strong octupole effects has emerged: With increasing rotation even and odd parity yrast states seem to merge into one single band of alternating parity where neighbouring levels are connected by fast El transitions. Such bands have been observed in218, 219, 220 Ra and220, 221, 222Th (see refs. [1, 2]). To extend the knowledge of high-spin states into the expected center of the octupole region [1] we have studied224Th using the208Pb(18O, 2n) reaction.

The proton microprobe at Heidelberg was used to measure the intracellular calcium distribution in two tip growing plant cells, the pollen tube of Lilium longiflorum and the protonema tip cell of the moss, Funaria hygrometrica . The cells were either chemically fixed with glutaraldehyde and air dried or frozen in melting nitrogen and freeze dried. Some samples were additionally pretreated with calcium interacting drugs. The specimens were measured with a proton beam of 3 MeV, focused to a point for X-ray spectra or to a line for scanning analysis. Thereby the cells were moved automatically step by step along the beam, in order to measure profiles of elemental distribution. Independent of the fixation technique the cells revealed a higher calcium content at their tips as compared to the base. The shape of the calcium distribution however depended strongly on the fixation technique. The calcium interacting drugs additionally influenced in different ways the content and distribution of cellular calcium. The results confirm the postulated tip-to-base calcium gradient in tip growing plant cells. Among other factors, calcium is assumed to regulate polar secretory processes that are required for tip growth.

The elemental distribution in tissue samples at the cellular and subcellular level is of particular interest, if various functional states of a specific structure are to be analyzed. A structure of increasing interest in kidney physiology is the part of the small arteries in the kidney that produces renin, a hormone which strongly affects the blood pressure. To help to ensure reliable measurements of the elemental content, preparation methods have been tested that are assumed to preserve the content as well as the distribution of the elements of interest, mainly Ca. The methods as used in other microprobe analyses turned out to fulfil some basic demands on preserving ionic distribution. The high analytic power of micro-PIXE in connection with a flexible on-line data taking system makes possible a discrimination between dislocation artefacts, contamination, or others, from the element distribution in intact tissue actually during measurement. This on-line assessment of the preparation quality is particularly helpful when analyzing delicate biological material that may be affected in a destructive way during several preparation steps.

The zinc distribution in pollen tubes ofLilium longiflorum was analysed by proton-induced X-ray emission (PIXE) with the Heidelberg proton microprobe. A very high zinc concentration was measured in the pollen tube tip region.