Ein richtungsempfindliches Zählrohr und seine Anwendung beim Li8→Be8*-Zerfall

A new type of proportional counter having a directional dependent efficiency has been used to measure the angular distribution of the α-particles of Be⁸ in the reaction Li⁸→Be^8*. From the experiment an upper limit of 10% for the amount of the Fermi contribution in the Li⁸ beta-decay is deduced.     

Die Temperaturabhängigkeit des magnetischen Barkhausen-Effekts. I

The apparatus described allows to measure the size distribution of Barkhausen discontinuities with a magnetic moment greater than 10^?6 e.m.u. in a temperatur range from liquid air up to the Curie point. We used the counting method, developed byTebble and his co-workers, in connection with a multichannel-analyzer. Nickel samples of different purity and of different thermal treatment have been investigated. The results are as follows: 1. The size distribution of two samples, having in practice the same hysteresis loop can show a completely different behaviour as a function of the magnetic field. 2. The number of great discontinuities is reduced more rapid with rising temperature than that of the smaller ones; thus leading to the conclusion, that the Barkhausen component of total magnetization is vanishing much stronger with increasing temperature than that of differential susceptibility. 3. The critical field strength, being characterized by a maximum in the number of discontinuities per unit field, shows the same temperature dependence as the coercive force. This critical field is only slightly dependent on the size of jumps. 4. The “average” magnetic moment of the discontinuities in the measured range of size appears to vary less with temperature than the spontaneous magnetization. 5. Above a temperature of about 270°C spontaneous jumps will be produced, even in a magnetic hard sample, by diminutive vibrations, such as speaking loud or coughing. 6. The Barkhausen part of total magnetization varies with temperature like the coercive force and therefore seems to be a structure-dependent quantity. The results of our measurements are discussed in connection with those of other authors.     

5D0→7F1 and 5D0→7F2 transition in europium doped halosulphates for mercury-free lamps

Polycrystalline Na₃SO₄F:Eu and NaMgSO₄F:Eu halosulphate phosphors prepared by a wet chemical method have been studied for its photoluminescence (PL) and thermoluminescence (TL) characteristics. Two well resolved peaks are observed at 593 nm and 614 nm, which are assigned to due to ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions of Eu³⁺ ions. TL is observed at temperatures between 100 °C and 300 °C. In this paper, we report PL emission spectra of Eu³⁺ and TL glow curves, which are more sensitive than the standard TLD-CaSO₄:Dy. The presented phosphors are applicable for the mercury free lamps and solid state lighting devices.     

Präzision der Emissionsspektrochemischen Analyseergebnisse I. Festlegung des “Totalen” Präzisionswetes

The definition of the final precision value of concentration determination at emission spectroscopy is discused. A method of succesive summing up of partial errors, taking into consideration as well the errors yielded at calibration functions construction, is sugested.     

Beugung elektromagnetischer Wellen in Braunbekscher Näherung. I

An approximation method proposed by Braunbek for the diffraction of scalar waves by plane obstacles, or apertures in a plane screen, is extended to the diffraction of electromagnetic waves. As an example, the diffraction of a linearly polarized plane electromagnetic wave normally incident on a circular aperture in a perfectly conducting plane screen and on a perfectly conducting plane circular disk is considered in detail. The results are compared with those obtained from the exact solution ofMeixner andAndrejewski and with the results ofKirchhoff's approximations. It is shown that, in contrast to theKirchhoff approximations,Braunbek's method leads in all cases to the correct ‘optical’ limits and represents a good approximation even for wavelengths comparable with the size of the obstacle. After a general formulation ofBraunbek's method in the electromagnetic diffraction problem, we calculate in the present paper the far field of the circular aperture and the transmission coefficient by means of the cross section theorem. The near field of the circular aperture and the circular disk will be considered in a subsequent paper.     

DasK/β+-Verhältnis beim Zerfall J128→T128

In the decay of J¹²⁸ the intensity of a weak positron activity was measured to be (3.1±0.7)·10^?5 per disintegration. The remeasurement of the totalK capture was found to be 0.059±0.007 in agreement with the results of other authors. From this theK/β ⁺-ratio of the decay to the ground state of Te¹²⁸ is 1800±400. Theoretical calculations ofK/β ⁺ for allowed transitions show that the maximum energy of the positrons is 245±12 keV. In the decay of Rh¹⁰⁴ and Lu^176m no positrons more than 5·10^?6 could be detected.     

Bestimmung der Konfigurationsmischungen im RaE aus den β−-Übergängen Pb210→Bi210→Po210

From the anomalies in theβ-decays of Pb²¹⁰ and Bi²¹⁰, relations between the shell model wave functions of the ground states of Pb²¹⁰, Bi²¹⁰ and Po²¹⁰ are derived. These relations are however not satisfied by wave functions calculated under the assumption of two-body central forces of zero range. We make use of the fact that such forces seem to be a good approximation for even-even-nuclei (in our case Pb and Po), but not for odd-odd-nuclei (Bi in our case), and derive the wave function for the 1^? level of Bi²¹⁰ from the wave functions of Pb²¹⁰ and Po²¹⁰ using the relations obtained from theβ-decay anomalies.     

Die Koeffizienten der Inneren Paarbildung bei den γ-Übergängen nach Co60→Ni60 und Pr142→Nd142

The coefficients ε of internal pair formation of the 1.17 and 1.33 MeV transitions in Ni⁶⁰ and of the 1.57 MeV transition in Nd¹⁴² were measured by detecting the annihilation radiation of the positrons. We obtained the values ε=(3.7±0.6)·10^?5 for Ni⁶⁰ and ε=(10.8±1.8)·10^?5 for Nd¹⁴². The results for Ni⁶⁰ are in good agreement with theoretical calculations. The 1.57 MeV transition in Nd¹⁴² is identified as electric quadrupole and the first excited level of Nd¹⁴² is determined to be 2⁺. By further measurements the partial transition from Pr¹⁴² to the first excited level of Nd¹⁴² was found to be (3.7±0.4)% per disintegration. NoK capture of Pr¹⁴² more than 2·10^?4 could be detected.     

The Z → c \bar c → γγ*, Z → b \bar b → γγ* triangle diagrams and the Z → γψ, Z → γϒ decays

The approach to the Z → γψ and Z → γ? decay study is presented in detail, based on the sum rules for the Z → c $ \bar c $ → γγ* and Z → b $ \bar b $ → γγ* amplitudes and their derivatives. The branching ratios of the Z → γψ and Z → γ? decays are calculated for different hypotheses on saturation of the sum rules. The lower bounds of Σ _ψ BR(Z → γψ) = 1.95 × 10^?7 and Σ_υ BR(Z → γ?) = 7.23 × 10^?7 are found. Deviations from the lower bounds are discussed, including the possibility of BR(Z → γJ/ψ(1S)) ～ BR(Z → γ?(1S)) ～ 10^?6, that could be probably measured in LHC. The angular distributions in the Z → γψ and Z → γ? decays are also calculated.     

金等离子体M带谱3d→4f和3d→5f电子离子碰撞激发强度

电子离子碰撞激发强度在超组态碰撞辐射模型中真实模拟非局域热动平衡金激光等离子体M带谱跃迁中离子的平均电离度、电荷态分布和能级布居数等离子的电离态特性是必不可少的.基于全相对论扭曲波电子碰撞激发计算程序REIE06,系统计算了高离化态金离子(Au51+、Au50+、Au49+)精细结构能级3d→4f和3d→5f的碰撞强度,计算中详细考虑了电子关联效应和Breit相互作用对碰撞强度的影响.计算结果与可获得的其它理论及实验结果进行了比较,取得了好的一致性.