Geology topics

F. Senftle

Publications and source records attributed to F. Senftle.

4 recordsLinked to original sources

USGS1977

Anisotropic magnetic susceptibility of erbium and ytterbium in zircon, ZrSiO4

Magnetic susceptibility measurements have been made for both Er- and Yb-doped (1̃0 3 ppm) zircon single crystals with the magnetic field perpendicular and parallel to the [001] axis. Large susceptibility anisotropies were found in both cases. Our observed anisotropies of ZrSiO 4 : Yb indicate small populations (1̃9%) of Yb ions at the axial (tetragonal) sites, as the susceptibility of ZrSiO 4 : Yb would be nearly isotropic if the Yb ions only occupied the orthorhombic sites. For Er 3+ in orthorhombic sites of zircon, our data indicate that the first excited state is paramagnetic with g x = 9 and g y 5̃ at 20 cm −1 above the ground state ( g x 0̃, g y 1̃5). The first excited state is quite similar to the ground states observed for Er 3+ in many host lattices

Journal of Physics and Chemistry of Solids↗

USGS1974

Problems encountered in the use of neutron methods for elemental analysis on planetary surfaces

From experimental studies of gamma rays from fast and thermal neutron reactions in hydrogeneous and non-hydrogeneous, semi-infinite samples and from Monte Carlo calculations on soil of a composition which might typically be encountered on planetary surfaces, it is found that gamma rays from fast or inelastic scattering reactions would dominate the observed spectra. With the exception of gamma rays formed by inelastically scattered neutrons on oxygen, useful spectra would be limited to energies below 3 MeV. Other experiments were performed which show that if a gamma-ray detector were placed within 6 m of an isotopic neutron source in a spacecraft, it would be rendered useless for gamma-ray spectrometry below 3 MeV because of internal activation produced by neutron exposure during space travel. Adequate shielding is not practicable because of the size and weight constraints for planetary missions. Thus, it is required that the source be turned off or removed to a safe distance during non-measurement periods. In view of these results an accelerator or an off-on isotopic source would be desirable for practical gamma-ray spectral analysis on planetary surfaces containing but minor amounts of hydrogen.

Nuclear Instruments and Methods↗

USGS1970

Neutron radiative capture methods for surface elemental analysis

Both an accelerator and a 252 Cf neutron source have been used to induce characteristic gamma radiation from extended soil samples. To demonstrate the method, measurements of the neutron-induced radiative capture and activation gamma rays have been made with both Ge(Li) and NaI(Tl) detectors, Because of the possible application to space flight geochemical analysis, it is believed that NaI(Tl) detectors must be used. Analytical procedures have been developed to obtain both qualitative and semiquantitative results from an interpretation of the measured NaI(Tl) pulse-height spectrum. Experiment results and the analytic procedure are presented.

Nuclear Instruments and Methods↗

USGS1954

Surface adsorption of Cs137 ions on quartz crystals

Adsorption tests were made on four large synthetic and three natural quartz crystals to see if surface defects might be detected by subsequent autoradiography techniques. The adsorbent used was radioactive Cs137 in a solution of Cs 137Cl. Natural quartz crystals adsorbed more cesium than the synthetic crystals. Certain surface defects were made evident by this method, but twinning features could not be detected.

Trace Elements Memorandum↗