Untersuchungen an Thalliumfluoridometallaten, TIx[SE(III)yFx+3y], der Lanthanoide mit SE = La-Nd, Sm-Lu

Das Ziel dieser Arbeit war es, neue Verbindungen des Typs Tlx[SEyFx+3y] mit den Lanthanoiden als SE auf einfachem, hydrothermalem Wege zu erhalten, zu charakterisieren und auf ihre mögliche Verwendung als Szintillatormaterial hin zu untersuchen. Zum Einen konnten die bislang unbekannten Verbindungen Tl[SE2F7], mit SE = Sm — Dy, er-folgreich synthetisiert werden. Die Darstellung dieser Verbindungen erfolgte hydrothermal im Autoklaven bei Temperaturen bis 210 bzw. 400 °C. Zwar gelang es nicht, Einkristalle zu erhalten und die Struktur auf diesem Wege zu ermitteln, dafür konnten die Verbindungen mittels Röntgenpulverdiffraktometrie, Atomabsorptionsspektrometrie, Ionenchromatogra-phie, dynamischer Differenzkalorimetrie und energiedispersiver Röntgenspektrometrie cha-rakterisiert werden. Anhand der Daten der Röntgenpulverdiffraktometrie konnte auf die Elementarzelle rückgeschlossen werden. Sie kristallisieren isotyp in der Raumgruppe (Nr. 255), mit 2 Formeleinheiten pro Elementarzelle. Zum Anderen wurden die ebenfalls bislang unbekannten Verbindungen Tl3[SEF6], mit SE = Ho — Lu, hergestellt. Die Darstellung der Verbindungen erfolgte im Autoklaven bei Temperaturen bis 400 °C. Es gelang auch im Falle dieser Verbindungsgruppe nicht, Einkristalle zu erhalten. Mittels der oben genannten Analysemethoden sowie mittels DFT-Rechnungen konnte eine Struktur für diese Verbindungen angegeben werden. Sie kristallisie-ren isotyp in einer kubisch innenzentrierten Zelle mit 2 Formeleinheiten pro Elementarzelle. Die Verbindungen wurden zudem auf ihre Fluoreszenzeigenschaften hin untersucht. Dabei zeigte sich, dass drei der Verbindungen, und zwar Tl[Tb2F7], Tl[Dy2F7] und Tl3[ErF6], deutliche Fluoreszenz zeigen. Die gemessenen Werte liegen sowohl bezüglich der Wellenlänge, als auch der Abklingzeiten, vergleichen mit literaturbekannten Stoffen, im Bereich von bekann-ten und anwendungsreichen Referenzen. Diese Eigenschaften könnten beispielsweise durch Doping mit anderen Elementen in tech-nisch bedeutende Bereiche verschoben werden.The aim of this study was to obtain, to characterize and to examine the possible use as a scintillator of new compounds of the type Tlx[SEyFx+3y] with the lanthanides as SE in a simple, hydrothermal method. On the one hand the hitherto unknown compounds Tl[SE2F7], with SE = Sm - Dy, were synthesized successfully. The preparation of these compounds was carried out hydrothermally in an autoclave at temperatures up to 210 or 400 °C. Although it was not possible to obtain single crystals and to determine the structure in this way, but the compounds were characterized by X-ray, atomic absorption spectrometry, ion chromatography, energy dispersive X-ray spectrometry and differential scanning calorimetry. Based on the data of X-ray powder diffraction the unit cells could be inferred. They crystallize isotypically in the space group (no. 255), with 2 formula units per unit cell. On the other hand, the also previously unknown compounds Tl3[SEF6], with SE = Ho - Lu, were synthesized. The preparation of the compounds was carried out in an autoclave at temperatures up to 400 °C. Also in the case of this group of compounds, it was not possible to obtain any single crystals. With the above-mentioned analysis methods and by means of DFT calculations a structure for these compounds could be specified. They crystallize isotype in a body-centered cubic cell with 2 formula units per unit cell. The compounds were also examined for their fluorescence properties. It turned out that three of the compounds, namely Tl[Tb2F7], Tl[Dy2F7] and Tl3[ErF6], show significant fluorescence. The measured values are in terms of both wavelength and the decay, comparing literature materials, ranging from known and application-rich references. These properties could be moved, for example, by doping with other elements in technically significant areas

Lossless State Detection of Single Neutral Atoms

We introduce lossless state detection of trapped neutral atoms based on cavity-enhanced fluorescence. In an experiment with a single 87-Rb atom, a hyperfine-state-detection fidelity of 99.4% is achieved in 85 microseconds. The quantum bit is interrogated many hundreds of times without loss of the atom while a result is obtained in every readout attempt. The fidelity proves robust against atomic frequency shifts induced by the trapping potential. Our scheme does not require strong coupling between the atom and cavity and can be generalized to other systems with an optically accessible quantum bit.Comment: 4 pages, 4 figure

Optically stimulated luminescence (OSL) dating of sand-filled wedges structures and their alluvial host sediments from Jonzac, Southwest France

International audienc

Optically stimulated luminescence (OSL) dating of sand-filled wedges structures and their alluvial host sediments from Jonzac, Southwest France

International audienc

The Twannberg iron meteorite strewn field in the Swiss Jura mountains: insights for Quaternary environmental conditions

The ~ 10 km 2 strewn field of the Twannberg type IIG iron meteorite is located in the Swiss Jura Mountains, 30 km northwest of Bern. The strewn field has been mapped by a group of citizen scientists since 2006, yielding more than 2000 meteorite fragments with a total mass of 152.7 kg until the end of 2022. With a terrestrial age of 176 ± 19 ka and a minimum pre-atmospheric mass of ~ 250 t, the Twannberg meteorite is a local time marker in an area with a poorly-known paleoenvironmental history. The Twannberg strewn field is located just outside of the maximum extent of ice during the Last Glacial Maximum (LGM). On the Mont Sujet, meteorites are size-sorted in a 6-km long section of the primary strewn field (altitude 945-1370 m a.s.l.), indicating a fall direction from east-northeast to west-southwest (azimuth approximately 250°). On the Twannberg plateau and in the Twannbach gorge, meteorites are not size-sorted and occur in a ~ 5.7-km long area associated with till and recent stream sediments (altitude 430-1075 m a.s.l.). The mass distribution of meteorites on the Twannberg plateau demonstrate that these meteorites were not found where they fell but that they must have been transported up to several km by glacier ice flow after the fall. The distribution of meteorites and of glacially transported Alpine clasts on the Mont Sujet and on the Chasseral chain indicates the presence of local ice caps and of an approximately 200-m higher Alpine ice surface with respect to the LGM at the time of fall. This high ice level during MIS 6 (Marine Isotopic Stage 6, 191-130 ka) indicated by the meteorite distribution is consistent with surface exposure ages of 50-144 ka from nearby resting erratic boulders at altitudes of up to 1290 m a.s.l., including the newly dated Jobert boulder (63 ka). These boulders indicate an ice level ~ 400 m higher than during LGM at a time not later than MIS 6. Post-LGM luminescence ages of loesscontaining meteorites on the Mont Sujet and 14 C ages of materials associated with meteorite finds indicate relatively young pedoturbation and increased oxidation of meteorites since ~ 7300 cal BP, possibly correlated with deforestation and enhanced erosion resulting from increased human activities since the Neolithic. This study shows that Twannberg meteorites in their palaeoenvironmental context provide valuable information about ice levels and transport directions during MIS 6 and about their interaction with the post-LGM environmental conditions. The unique Twannberg strewn field has the potential to reveal more valuable information