Monopole excitation of 4He in α-particle scattering from 12C, 13C,and 16O

The excitation of the O⁺ state in ⁴He at 20.1 MeV has been studied in α-scattering from ¹²C, ¹³C, and ¹⁶O at E_α=65MeV by measuring the decay $\text{α}{}^1\text{→}\text{p}\text{+}\text{t}$ with a coincidence method. DWBA calculations of this monopole transition using both microscopic and collective model transition densities are presented.     

Systematics of nn states with high spin: A study of the (α, 2He) reaction on fp shell nuclei

At 57 MeV bombarding energy the (α, ²He) reaction has been investigated on targets of ^54,56Fe, ^58,60,62,64Ni, ^64,66Zn, and ⁷⁰Ge. Selective excitation of the 2n configurations $\text{(}\text{f}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{7?}}$, , and $\text{(}\text{g}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}\text{2}\text{d}{}_{\mathrm{<mtext>5</mtext><mtext>2</mtext>}}\text{)}{}_{\mathrm{6+}}$ was observed in all final nuclei. A linear A and T dependence of the binding energies of these states was observed. This systematic behaviour is well described by the Bansal-French model. The values obtained for the strength of the isoscalar and the isovector parts of the particle-hole interaction are consistent with the average of the values describing the corresponding single-particle states.     

Experimental study of high spin states in the ground state bands of158,160Er,164,166Yb,and168Hf

Ground state rotational bands in the deformed doubly-even rare earth nuclei^158,160Er,^164,166Yb, and¹⁶⁸Hf have been observed in (α, 8n γ) reactions. The γ-spectra associated with these reactions were studied in-beam using conventional spectroscopic methods. In all five nuclei the nuclear moment of inertia of the ground state rotational states was found to increase abruptly as higher spin states were attained. In a plot of the moment of inertia as a function of the angular velocity all these five nuclei display “backbending” curves. Moreover, in¹⁵⁸Er and¹⁶⁶Yb, the curves after passing through a maximum bend subsequently downwards.     

Neue Wege der serologischen HIV-Diagnostik

Ohne Zusammenfassung

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New approaches to serological HIV diagnostics

     

Experimental investigation of mode coupling in a multimode graded-index fiber caused by periodic microbends using computer-generated spatial filters

The results are described of an experimental investigation of mode coupling in a multimode graded-index fiber as a function of the periodic microbend amplitude. Computer-generated holograms were used as mode selecting spatial filters for measurements of the modal power distribution. The experimental data are in a good qualitative agreement with theoretical predictions. The results obtained may be helpful in the development of amplitude-type graded-index fiber sensors with high sensitivity.     

Birefringence,X-ray and neutron diffraction measurements on the structural phase transitions of (CH3NH3)2 MnCl4 and (CH3NH3)2FeCl4

We used optical birefringence, X-ray and neutron diffraction methods with single crystals to study the structural phase transitions of the perowskite-type layer structures of (CH₃NH₃)₂MeCl₄ with Me=Mn, Fe. The Mn-compound shows the following structural transitions at 394 K — a continuous order-disorder phase transition from tetragonal symmetry $\text{I4}\text{mmm}$ to orthorhombic space group Abma (Cmca in reference 10); at 257 K — a discontinuous transition to a second tetragonal modification; at 95 K — a discontinuous transition to a monoclinic phase. For the Fe-compound the corresponding transition temperatures are 328 K and 231 K, respectively. A low temperature monoclinic phase could not be observed. The lattice parameters of the different modifications were determined as a function of temperature. The temperature dependent course of the order parameter has been investigated for the order—disorder transition. For both compounds, all the methods used gave the same value for the critical exponent of β = 0.315.     

Birefringence in tetragonal antiferromagnets

It is shown that measurements made in the flop phase of antiferromagnets can lead to an unambiguous determination of the relative importance of the possible microscopic origins of the magnetic linear birefringence. From our experiments we conclude that in GdVO₄ exchangestriction is the dominant contribution.     

Observation of anomalous behaviour of the nuclear moment of inertia at large rotational frequencies in Yb and Hf

The (α, 8n) reaction has been used to produce high-spin states in ¹⁶⁴Yb and ¹⁶⁸Hf. In both cases a sharp increase of the moment of inertia as a function of rotational frequency was observed at I = 12.