Suche nach Strahlungsprozessen zweiter Ordnung beim Zerfall von Ag109m

The decay of an excited state by the emission of twoγ-quanta (γ γ-transitions) or two conversion electrons (e e-transitions) or oneγ-quantum and one conversion electron (γ e-transitions) is expected as a second order radiation process. The decay of Ag^109m was examined for such events using a special arrangement of two NaJ-scintillation counters in coincidence. The energies of coincident quanta were displayed on the two axes of an “X-Y”-Oscilloscope respectively. For the ratio ofγ γ-transitions to one-quantum transitions an upper limit of\(\frac{{W_{\gamma \gamma } }}{{W_\gamma }} \leqq 1,9 \cdot 10^{ - 5} \) was obtained. Furthermore theγ-spectrum in coincidence withK X-rays was studied. From these measurementse e- andγ e-transition rates can be calculated for the case ofK shell conversion. The results obtained are:

$$\frac{{W_{^e K^e K} }}{{W_\gamma }} = \left( {8,1_{ - 1,7}^{ + 0,6} } \right) \cdot 10^{ - 3} and\frac{{W_{\gamma ^e K} }}{{W_\gamma }}< 1,5 \cdot 10^{ - 3} .$$     

Zur Störung der Kohärenz zweiter Ordnung durch Wechselwirkung

A definition of the disturbance of the second order coherence of a photon field, scattered by an electron, is formulated within the framework of quantum electrodynamical coherence theory. As a special case forward scattering is considered, thus yielding a simple relation with the matrix element for one-photon-scattering. The scattering on a free polarized electron is treated as an example.     

Die Physik am Ende des 18. Jahrhunderts und Lazare Carnot

Physics at the End of the 18th Century and Lazare Carnot It is not by accident that the evolution of classical physics in the modern sense, the introduction of the metric system, and the foundation of “Annalen der Physik” came together 200 years before. The twofold revolution, the bourgeoise and industrial revolution, affected lastingly the development of natural sciences.     

Phasenumwandlung zweiter Art als kritische Erscheinung eines inneren Phasengleichgewichtes

It is demonstrated that the transition in a state with two internal phases is a second order phase transition. The term internal phases means phase-like regions inside the system which are not separated by boundaries in the sense of ordinary phase boundaries, and the dimensions and shape of which as well as their properties as such are object of an equilibrium. In a generalization (quasi phases) a long ranged correlation of alternating or periodical character is considered as a typical element of the low temperature state. Such states can be described thermodynamically with the help of a new pair of variablesQ-η. The transition intoQ-η-T is generally analogous to the critical point of ordinary phase transitions inP-V-T, andη ～(?t)^1/3 andC _p～(?t)^?2/3 with a small constant of proportionality are obtained (t=T-T _u). Using the Pippard-relations in the formV-V _γ=(dT _γ/dP) (S-S _γ) the low temperature behaviour of the entropy and density surface as a function ofP andT near the transition line can be completely described. E.g. the saturation magnetization of a ferromagnetic model is derived proportional to (?t)^1/3. Under the action of a magnetic field the transition will be of first order when the saturation magnetization is achieved, without the outer field being analogous toP orQ. Should only one internal phase differ from the high temperature state we obtain an edge point (x=0 analogous to theμ ₁?x-diagram of solutions) with finite jump inC _p andη～({t). A possible relationship to the BCS- model of the supraconductors is indicated.     

Die Übergangstemperatur verschiedener Supraleiter zweiter Art unter hydrostatischem Druck

An apparatus for production of hydrostatic pressure is described using a mixture of n-pentane and iso-pentane, which transmits pressure uniformly still at low temperatures. The superconductive transitions of the A 15(β- W type)-compounds Nb₃Sn, Nb₃Al, V₃Si and the B 1(NaCl type)-compound NbN have been measured under pressure up to 18 · 10³ kp/cm². The transition temperatures of the compounds V₃Si and NbN are increasing with pressure. Further measurements have been done on some selected ternary compounds, e.g. Nb₃(Al_1?x Ge _x ), to prove some predictions for the effect of pressure on superconductive transition.