Ungewöhnliches aus unserer Pflanzen- und Tierwelt

Beobachtungen des Löfflers im deutschen Binnenland sind außergewöhnlich selten. Das verwundert, denn aus ihren Brutgebieten in Europa ziehen diese auffälligen Vögel alljährlich nach Afrika und zurück. Aber die niederländischen wandern die Atlantikküste entlang. Nur im Rheintal treten immer wieder Löffler einzeln oder in Trupps auf (GEBHARDT/SUNKEL 1954). An der Küste der Nordsee streifen holländische Tiere durch die Watten weit nach O bis N. 1962 kam es zu einer gesicherten, aber erfolglosen Brut auf der Insel Memmert (RINGLEBEN 1978). Jetzt kommt der Kreis Höxter dazu. Am 10. September 1987, 16.00 Uhr, sah August Held, Amelunxen, als erster das auffällige Tier in seiner Heimatgemarkung

Grinding of optical glasses with cup wheels - Α new way to generate polishable surfaces

Conventionally the machining sequence of optical glass lenses consists of rough grinding, fine grinding and polishing. At this time the research in glass machining techniques concentrates on rough grinding and fine grinding, especially tool and process optimisation. The shown results of rough grinding tests offer the possibility to eliminate the fine grinding process out of the machining sequence. The surface quality which can be reached depends, besides other circumstances like machine parameters, on the glass material. This is described just as the used research methods and measuring techniques

Collinear laser spectroscopy of highly charged ions produced with an electron beam ion source

Collinear laser spectroscopy has been performed on He-like C$^{4+}$ ions extracted from an electron beam ion source (EBIS). In order to determine the transition frequency with the highest-possible accuracy, the lineshape of the fluorescence response function was studied for pulsed and continuous ion extraction modes of the EBIS in order to optimize its symmetry and linewidth. We found that the best signal-to-noise ratio is obtained using the continuous beam mode for ion extraction. Applying frequency-comb-referenced collinear and anticollinear laser spectroscopy, we achieved a measurement accuracy of better than 2\,MHz including statistical and systematic uncertainties. The origin and size of systematic uncertainties, as well as further applications for other isotopes and elements are discussed

Collinear Laser Spectroscopy of 2 3 ⁣S1→2 3 ⁣P ⁣J2\,{}^3\!S_1 \rightarrow 2\,{}^3\!P_{\!J} transitions in helium-like 12C4+^{12}\mathrm{C}^{4+}

Transition frequencies and fine-structure splittings of the $2\,{}^3\!S_1 \rightarrow 2\,{}^3\!P_{\!J}$ transitions in helium-like $^{12}\mathrm{C}^{4+}$ were measured by collinear laser spectroscopy on a 1-ppb level. Accuracy is increased by more than three orders of magnitude with respect to previous measurements, enabling tests of recent non-relativistic QED calculations including terms up to $m\alpha^7$. Deviations between the theoretical and experimental values are within theoretical uncertainties and are ascribed to $m\alpha^8$ and higher-order contributions in the series expansion of the NR-QED calculations. Finally, prospects for an all-optical charge radius determination of light isotopes are evaluated

On the performance of wavelength meters: Part 2 — frequency-comb based characterization for more accurate absolute wavelength determinations

Wavelength meters are widely used for frequency determinations and stabilization purposes since they cover a large wavelength range, provide a high read-out rate and have specified accuracies of up to 10⁻⁸. More accurate optical frequency measurements can be achieved with frequency combs but only at the price of considerably higher costs and complexity. In the context of precise and accurate frequency determinations for high-resolution laser spectroscopy, the performance of five different wavelength meters was quantified with respect to a frequency comb. The relative precision as well as the absolute accuracy has been investigated in detail, allowing us to give a sophisticated uncertainty margin for the individual instruments. We encountered a prominent substructure on the deviation between both device types with an amplitude of a few MHz that is repeating on the GHz scale. This finally limits the precision of laser scans which are monitored and controlled with wavelength meters. While quantifying its uncertainty margins, we found a high temporal stability in the characteristics of the wavelength meters which enables the preparation of wavelength-dependent adjustment curves for wide- and short-ranged scans. With this method, the absolute accuracy of wavelength meters can be raised up to the MHz level independently from the wavelength of the reference laser used for calibrating the device. Since this technique can be universally applied, it can lead to benefits in all fields of wavelength meter applications

Collinear Laser Spectroscopy of Helium-like ¹¹B³⁺

Collinear laser spectroscopy in the 1s2s³S₁→1s2p³P₀,₂ transitions of helium-like ¹¹B³⁺ was performed using the HITRAP beamline at the GSI Helmholtz Centre. The ions were produced in an electron beam ion source, extracted, and accelerated to a beam energy of 4 keV/q. Results agree with previous measurements within uncertainty. Thus, it was demonstrated that the metastable state in He-like ions is sufficiently populated to carry out collinear laser spectroscopy. The measurement is a pilot experiment for a series of measurements that will be performed at a dedicated collinear laser spectroscopy setup at TU Darmstadt with light helium-like ions