[en] Direct detection of radioisotopes with conventional mass spectrometers is possible when the potential background atoms, in particular stable isotopes of the same mass (isobars) or molecules of similar mass are present in sufficiently low concentrations. Most of the long lived radioisotopes of interest for dating purposes however, occur in such small concentrations that their peak in the mass spectrum is obscured by the stable isobar and molecule distributions. The key idea of the new AMS technique which allows us to measure directly such small concentrations is the acceleration of the sample atoms to MeV energies and to use various filter processes and particle identification techniques developed for nuclear physics research to eliminate the isobaric and molecular interferences. The detection methods used for each radioisotope depend on the dominant background atoms and these in turn depend on the specific accelerator used. The problems encountered in transforming an existing particle accelerator into a high precision dating tool are considerable and have been solved only recently for one type of accelerator, notably the tandem van de Graaff. For this reason the description of the AMS method and some of its applications is restricted to this type of accelerator only. (Auth.)

[en] Recent advances in the detection of some of the most important cosmogenic long-lived radioisotopes using the technique of accelerator mass spectrometry, in particular, the developments in accuracy approaching 0.3% for ¹⁴C and 1-3% for ¹⁰Be, ²⁶Al, ³⁶Cl and the improvement of the detection limits at low acceleration voltages, are discussed. Some novel applications of these radionuclides in archaeology, oceanography, climatology and hydrology are given. (orig.)

[en] The properties of the continuum X-ray spectra observed in relatively slow collisions between two atoms with atomic numbers Z(p) and Z(t) have been investigated for 36 different systems having combined atomic numbers Z(u)=Z(p)+Z(t) between 22(F+Al) and 184(U+U) at beam energies between 3 and 980 MeV. In all cases the spectra exhibit an anisotropy which has a photon-energy dependent structure. The structure appears to be caused by molecular-orbital transitions occurring predominantly at the distance of closest approach of the two colliding nuclei. Possible mechanisms responsible for this effect and its application for a spectroscopy of superheavy quasi-molecules are discussed

[en] In the absence of written records that go back more than 150 years, the frequency of major earthquakes in the seismically active regions of the western United States can only be deduced from geologic evidence. Scarps along the Wasatch fault near Salt Lake City, Utah exhibit cumulative surface displacements as large as 10 meters in alluvial deposits that post-date the recession of Lake Bonneville, 12,000 years ago; although no damaging earthquakes have occurred since the area was settled. Recent trenching studies by Swan et. al. have exposed ancient surface soil layers in which discontinuities reveal a sequence of significant surface faulting events. Radiocarbon dates of detrital charcoal from these deposits would be a record of earthquake recurrence intervals, vital data for contemporary earthquake hazards assessment. Most of the samples collected so far have been too small for conventional beta-decay counting. We report a successful radiocarbon assay by direct atom counting of four milligram-sized specimens from the Wasatch study

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[en] A photon energy dependent anisotropy of the molecular X-rays produced in quasiadiabatic heavy-ion-atom-collisions was predicted and observed by several authors. These and some additional new results can prove the molecular origin of this effect. The experimental data for six symmetric systems (Al-Al, Ca-Ca, Fe-Fe, Ni-Ni, Ag-Ag, I-I) and five asymmetric cases (Cl-Ni, Fe-Ni, Ni-Fe, Ag-I, I-Ag) at different beam energies in the range of 20 to 62.5 MeV give a check of the Z²-scaling not only for KX-rays but also for L- and M anisotropy peaks. The positions of the bumps are all as expected clearly above the united atom limit. They are independent of the beam energy. Some models to describe the anisotropy phenomena are discussed. A new striking feature was found with the fine structure of the X-ray anisotropies. These periodic intensity fluctuations appear if the evaluation is performed with sufficiently good energy resolution. There is an evidence, that the anisotropy effect can be used to perform spectroscopy of arbitrary two-centre levels. However caution is required if one is to apply these ideas to the spectroscopy of superheavy systems. (MKO)

[en] Results on the impact parameter dependence of L-shell vacancy production during heavy ion collisions are discussed in the frame-work of molecular orbital (MO) excitation mechanisms. It appears that excitation in the 4fsigma MO and vacancy transfer in the 3psigma, 3dπ, and 3dsigma MO through 3pπ - 3psigma and 3ddelta - 3dπ - 3dsigma rotational couplings reproduce fairly well experimental results for near-symmetric systems. Using the experimental results on the impact parameter dependence of the projectile L-vacancy production probability, the multiple collision process of Meyerhof et al. of 2psigma-vacancy production is considered in the case of I - Ag collisions. It is found that this process dominates K-vacancy production at large impact parameters, whereas at small impact parameter the experimental results can be explained by a single-collision direct excitation process from the coupled 2pπ and 2psigma MO's. 24 references, 6 figures