Circular photogalvanic effect at inter-band excitation in semiconductor quantum wells

We observed a circular photogalvanic effect (CPGE) in GaAs quantum wells at inter-band excitation. The spectral dependence of the CPGE is measured together with that of the polarization degree of the time-resolved photoluminescence. A theoretical model takes into account spin splitting of conduction and valence bands.     

Kinetics and mechanism of the explosive reaction of carbon monoxide and oxygen

A new technique is described for quantitative measurement of the conditions of reactant concentration at ignition in mixtures of carbon monoxide and oxygen. A thin film of carbon covering the surface of a quartz reaction vessel reacted with oxygen to form carbon monoxide and small quantities of water. Explosions were observed above 900 K over the pressure range 15–100 torr with ratios of CO/O₂ far below those hitherto explored. The onset of explosion was favored by the addition of hydrogen, methane, and water and was inhibited by the addition of inert gases. A simple mechanism predicts the occurrence of an explosion over a wide range of product composition and total pressure.     

Time resolved magnetization dynamics of ultrathin Fe(001) films: spin-pumping and two-magnon scattering

The time-resolved magnetic response of ultrathin epitaxial Fe(001) films grown on GaAs(001) and covered by Au, Pd, and Cr capping layers was investigated by time and spatially resolved Kerr effect measurements. The magnetization was excited by an in-plane magnetic field pulse using the transient internal field generated at a Schottky barrier while the wavelength of the excitation (resonant mode) was roughly 4 microm. Each of the three cap layers affected the spin relaxation in a unique way. Au cap layers resulted in the bulk Gilbert damping of the Fe film. Pd cap layers caused an additional Gilbert damping due to spin-pump or spin-sink effects. Cr cap layers lead to a strong extrinsic damping which can be described by two-magnon scattering. In this case the strength of the extrinsic damping can be controlled by a field induced shift of the spin wave manifold with respect to the excited k vector.     

Quantitative analysis of magnetic excitations in Landau flux-closure structures using synchrotron-radiation microscopy

We have measured the excitation spectrum of six micron magnetic squares using x-ray magnetic circular dichroism. We observe all three excitations expected in a Landau flux-closure pattern. High temporal and spatial resolution allows quantitative analysis of the excitations. A short magnetic in plane pulse excites the magnetic element and we observe precessional motion of the magnetization within the domains as well as a domain wall mode and vortex motion. The vortex moves perpendicular to the excitation field and relaxes without showing a circulating orbit.     

Micromagnetic dissipation, dispersion, and mode conversion in thin permalloy platelets

Micron-sized ferromagnetic Permalloy disks exhibiting an in-plane ferromagnetic vortex structure are excited by a fast rise time perpendicular magnetic field pulse and their modal structure is analyzed. We find azimuthal and axial modes. By a Fourier filtering technique we can separate and analyze the time dependence of individual modes. Analysis of the experimental data demonstrates that the azimuthal modes damp more quickly than the axial modes. We interpret these results as mode conversion from low-frequency azimuthal modes to the fundamental mode which is higher in frequency, i.e., mode-mode coupling in a system with a single Landau-Lifshitz-Gilbert phenomenological damping constant alpha.     

Centrality dependence of charged hadron transverse momentum spectra in Au+Au collisions from sqrt[s(NN)]=62.4 to 200 GeV

We have measured transverse momentum distributions of charged hadrons produced in Au+Au collisions at sqrt[s(NN)]=62.4 GeV. The spectra are presented for transverse momenta 0.25相似文献   

Spin-wave eigenmodes of permalloy squares with a closure domain structure

Quantized spin-wave eigenmodes in single, 16 nm thick and 0.75 to 4 mum wide square permalloy islands with a fourfold closure domain structure have been investigated by microfocus Brillouin light scattering spectroscopy and time resolved scanning magneto-optical Kerr microscopy. Up to six eigenmodes were detected and classified. The main direction of the spin-wave quantization in the domains was found to be perpendicular to the local static magnetization. An additional less pronounced quantization along the direction parallel to the static magnetization was also observed.     

“Selenosulfonation”: the addition of selenolsulfonates to olefins

The reaction of phenyl areneselenolsulfonates with unhindered olefins affords β-phenylselenosulfone adducts, usually with high regio- and stereoselectivity.