Messung der Lebensdauer angeregter Kernniveaus von Al28, Cs133, Pr141, W182 und Pt195

The halflife of excited states in some nuclei has been measured by the method of delayed coincidences. Two different experimental arrangements have been used: a conventional scintillation counter equipment and a fast gasfilled parallelplate avalanche-counter. The results of these measurements are: 31 keV-level in Al²⁸:T _1/2=(1.91±0.08) · 10^?9 sec, 81 keV-level in Cs¹³³:T _1/2=(6.25±0.05) · 10^?9 sec, 145 keV-level in Pr¹⁴¹:T _1/2=(1.85±0.03) · 10^?9 sec, 100keV-level in W¹⁸²:T _1/2=(1.45±0.04) · 10^?9 sec, 1290 keV-level in W¹⁸² T _1/2=(1.05±0.03) · 10^?9 sec, 99 keV-level in Pt¹⁹⁵:T _1/2≦1.6 · 10^?10 sec, 129 keV-level in Pt¹⁹⁵:T _1/2=(6.2±0.7) · 10^?10 sec. These experimental values are discussed and compared with theoretical model predictions.     

Messung der Lebensdauer von Elektronen im 3P- und 4D-Zustand des Natrium

Lifetimes of electrons in the 3P- and 4D-levels of sodium are measured. The sodium-atoms are excited by short pulses of electrons with energies between 2 and 8 eV. The time dependence of the emitted light is determined by direct oscillographing via photomultiplier as well as by counting single quantas. The counting technique corresponds to the delayed coincidence method and employs a sampling oscilloscope. Lifetimes of the 3P- and 4D-levels were found to be 14.0 and 52.1 nsec respectively. From these values the absorption oscillator strengths 1.11 and 0.095 were calculated for the 3S-3P- and 3P-4D-transitions.     

Messung von Lebensdauern und relativen Besetzungszahlen angeregter Zustände des Wasserstoffatoms mit der Methode der Ionenstrahlspektroskopie

H ⁺₂ ions or protons, accelerated to energies between 80 and 300 keV, are sent through a thin carbon target. Light emitted by the excited atoms moving out of the foil with a definite velocity is analyzed using interference filters and a cooled photomultiplier. Intensities of theH _α,H _β, andH _γ lines are measured as functions of the distance from the foil. The data is analyzed with a computer program, which yields (in agreement with theory) mean lives of the hydrogen atom excited states involved, and the relative initial state populations of states belonging to the same principal quantum number. There is no indication of cascading.

     

Lebensdauermessungen von angeregten Kernniveaus mit der Methode der verzögerten Koinzidenzen

The lifetimes of several excited nuclear states were measured with the method of delayed coincidences and a time-to-pulse-height converter. The following results were obtained:

     

Messung der Paarkonversionskoeffizienten von59Co

Internal pair formation propabilities in⁶⁰Ni and⁵⁹Co have been determined by a positron annihilation method. The electrons from the β^?-decay of⁵⁹Fe were measured in triple coincidence with annihilation quanta originating from pairs produced in the deexcitation of the⁵⁹Co nucleus. By this triple coincidence technique it was possible to measure separately the pair formation coefficients Γ for transitions in⁵⁹Co. The observed values Γ_1.29=(3.7±0.4)×10^?5 and Γ_1.10=(0.5±0.1)×10^?5 are in agreement with theoretical calculations forE2-radiation.     

Optische Messung der Hyperfeinstrukturaufspaltungen von CoI-Termen

The spectrum of⁵⁹CoI has been investigated by a direct optical method. The hyperfine-splitting of 61 lines between 3,412 and 6,082 Å has been determined. A special numerical technique has been used to decompose the unresolved profiles. For 36 niveaus theA-factors and from these the magnetic field strength at the nucleus have been obtained and also someB-factors. The accuracy of theA-factors lies between 0.5 and 5 percent.     

Messung der zirkularen Polarisation der Inneren Bremsstrahlung von90Y

The circular polarization of the Internal Bremsstrahlung (IB) of⁹⁰Y was measured with a Compton polarimeter according to Beard and Rose. The results are compatible with the theoretical predictions of Ford and Martin [8], who include “detour transitions” in their calculations of the circular polarization. Measurements ofΒ-γ-correlations of the IB of⁹⁰Y are discussed, which suggest the consideration of detour transitions too.     

Messung der Glorienstreuung des totalen Streuquerschnitts von Na-Hg

The velocity dependence of the total cross section of Na-Hg has been measured in the velocity region from 750 to 2700 m/s. The extremaN=5.0 toN=11.0 are well resolved. The glory extrema indexing was performed by counting the number of measured rainbow extrema in the differential cross section at corresponding velocities. The results from the data evaluation method proposed by Bernstein and O'Brien are compared with the results from an inversion procedure for this system. Significant errors can result from the use of the Bernstein-O'Brien method except in the case of the expressiona ₁?r _m .     

Messung der Verweilzeit von He-Atomen an Glasoberflächen

Mean sticking times of helium on a glass surface are determined at very low pressures from nonstationary molecular flow through glass capillaries. The temperature range covered is 13.8 °K to 20.4 °K. Resulting sticking times are of the order of 10^?7 to 10^?5 sec. They show a characteristic dependence on temperature and pressure. These measurements can be interpreted by means of a simple model: He-atoms mostly are bound to the surface with an adsorption energyE of 229 cal/mol?0.01 eV (±20%). However with a probability of 10^?4 the energy is 530 cal/mol?0.023 eV (±6%). In both cases sticking times τ follow the equation τ=τ₀exp(E/RT) where τ₀ is about 10^?9 to 10^?10 sec.     

Messung der von Elektronenlawinen erzeugten Raumladungsfelder mittels einer Sondenlawine

The electrical fields due to the space charge of positive ions in a plane-parallel discharge gap are measured by means of an electron avalanche. The measurements were made in a N₂-CH₄ gas mixture (5% CH₄) at a total pressure of 210 Torr (20 °C) in a 3 cm gap, at a voltage UD (static breakdown potential). The positive ions are produced by electron avalanches, which are released from a broad area by an UV flash at the cathode. The ions so produced drift towards the cathode with a drift velocity v₊. After a timeT the probe avalanche is started by a second UV flash in the symmetry axis of the charge distribution. From its temporal growth, which is given by the relation\(i_s (t) \sim \delta v\_\exp \left( {\int\limits_0^t {\alpha v\_dt} } \right)\), one can evaluate the space charge field E(z) of the positive ions. The measured fields are in good agreement with those predicted by calculations.     

Markierungsprobleme bei der Messung von Verweilzeitspektren in Hochdruckhydrieranlagen

Es wird über Untersuchungen des Verweilzeitverhaltens der flüssigen Phase in einer kleintechnichen Hochdruckhydrieranlage berichtet. Die Messungen wurden mit Hilfe des radioaktiven Nuklids ⁸²Br in Form von Methylenbromid (CH₂Br₂) durchgeführt. Untersucht wurde das Verweilzeitverhalten bei verschiedenen Durchsätzen und unterschiedlichen Betriebsweisen der Anlage, wobei Temperaturen gewählt wurden, bei denen keine Hydrierreaktionen ablaufen.     

γγ-Winkelkorrelationsmessungen an155Gd

Two Ge(Li) detectors were used to investigateγ transitions in¹⁵⁵Gd produced by the decay of¹⁵⁵Eu. Relative intensities were determined for the weak lines at 18.8, 26.5, 58.0, and 86.0 keV. Angular correlations for fourγ cascades were measured. As results, the mixing ratios of the 45.3 and 86.5 keVγ lines were determined, and it was shown that the sign of the mixing ratio is positive for theγ line at 18.8 keV and negative for the line at 60.0 keV. Spins 5/2 and 3/2 for the 86.5 and 105.3 keV levels, respectively, are consistent with the data, and spin 5/2 for the 105.3 keV level is inconsistent with it.