Loop calculations for the non-commutative U ⋆(1) gauge field model with oscillator term

The European Physical Journal C - Motivated by the success of the non-commutative scalar Grosse–Wulkenhaar model, a non-commutative U ⋆(1) gauge field theory including an...     

First-order relativistic corrections and spectral concentration

Pauli Hamiltonians with first-order relativistic corrections according to Foldy and Wouthuysen are rigorously studied applying methods of singular perturbation theory. The results include a proof of first-order spectral concentration in the non-relativistic limit and a characterization of first-order pseudoeigenvalues by means of formal perturbation theory.     

Nucleon transfer reactions to rotational states induced by206, 208Pb projectiles

In a systematic study of nucleon transfer reactions accompanied by Coulomb excitation we have bombarded¹⁵²Sm,¹⁶⁰Gd and²³²Th with^{206, 208}pb beams at incident energies close to the Coulomb barrier. Particle-gamma coincidence techniques were used to identify excited states of reaction products populated through inelastic scattering and in nucleon transfer reactions. One-neutron stripping and pick-up reactions on¹⁵²Sm were observed leading to known states of the rotation alignedi _13/2-bands in¹⁵³Sm and¹⁵¹Sm. In the¹⁶⁰Gd+^{206, 208}Pb systems no significant population of low lying states of product nuclei was found in the nucleon-transfer channels. Large cross sections were observed for one- and two-neutron pick-up from²³²Th at an incident energy of 6.4 MeV/u. Around the grazing angle they are of the same order of magnitude as the cross section measured for inelastic scattering. The results are analyzed in the framework of semiclassical models.     

Simulation of photoacoustic IR spectra of multilayer structures

In photoacoustic spectroscopy a sample in a closed gas cell is heated by periodically modulated light. When thermal waves generated by the warm spots inside the sample reach the surface they heat up the adjacent gas. This causes periodic pressure variations which are detected by a microphone. We present a matrix method which enables us to calculate the surface temperature of a multilayer structure with any number of homogeneous lamellae of any optical and thermal properties. This method is based on the multiple reflections and interferences of thermal waves inside the system of lamellae. Photoacoustic spectra simulated by this method reproduce the measured spectra. This is demonstrated for a mylar (polyethyleneterephthalate, PETP) foil coated with a thin antimony layer.     

Atomgewichte

Ohne Zusammenfassung     

Infrared spectroscopy of oxide layers on technical Si wafers

Measurements of the reflectance and transmittance in the infrared part of the spectrum (400...4000cm^–1) are carried out on oxidized Si wafers. Intrinsic dielectric properties of the oxide layers prepared by various methods are derived from experimental data. The dielectric functions of the oxides can be fitted by oscillator models. The related model parameters are compared with those of other SiO₂ samples, as crystals and glasses. Optical arrangements to detect and characterize layers of thicknesses down to 3 nm are discussed. In particular, it is shown that experiments with polarized light at oblique incidence up to 80° are a powerful tool to characterize those layers.Experiments are reported to determine, in addition, extrinsic properties such as B and P atoms in the oxide layer or defects due to an ion implantation treatment.Conditions are discussed which should be applied to obtain the best quantitative analysis of the defect concentration.     

Ueber eine neue Form von Photometern

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Triaxiality andγ-softness in196Pt

The nuclear level structure and electromagnetic properties of¹⁹⁶Pt were investigated withγ-spectroscopic techniques using multiple Coulomb excitation by²⁰⁸Pb projectiles. Particle-γ, and particle-γ-γ coincidences were measured over a wide range of scattering angles.E2-transition moments and static quadrupole moments have been determined by a comparison of experimental scattering-angle dependentγ yields with calculated yields in a largely model-independent procedure. The results are compared with different theoretical models: the Asymmetric-Rotor Model, the Generalized Collective Model, and the Interacting Boson Model. The best agreement is obtained with the Generalized Collective Model representing a triaxial nucleus which is soft in theγ degree of freedom.     

Paraffine

Ohne Zusammenfassung