Ac-Josephson effect in YBa2Cu3O7/YBa2Cu3O7 point contact junctions

The ac-Josephson effect could be demonstrated up to dc voltages of 20 mV on the I–V characteristic of adjustable YBa₂Cu₃O₇/YBa₂Cu₃O₇ point contacts at 4.2 K. A detailed analysis of the rf power dependence of the size of microwave-induced constant voltage steps is given for microwave frequencies of 70 and 90 GHz. The results prove that electron pairing is responsible for the superconductivity in YBa₂Cu₃O₇.     

Soft X-ray emission and the local densities of states of the Cu x Rh1−x alloy system

Soft X-ray emission experiments on Cu _x Rh_1–x alloys for the compositionsx=0.0, 0.05, 0.10, 0.80 and 1.0, have been performed. In this paper we present the spectra of Cu-and Rh-L _III core level-conduction band transitions. Using the data of recent self-consistent KKR-CPA electronic structure calculations we evaluate the corresponding SXS-cross sections and compare these theoretical results to our measurements.     

Formation of Fe i –B pairs in silicon at high temperatures

We report on the detection of Fe _i –B pairs in heavily B doped silicon using ⁵⁷Fe emission Mössbauer spectroscopy following implantation of radioactive ⁵⁷Mn⁺ parent ions (T _1/2?=?1.5 min) at elevated temperatures >?850 K. The Fe _i –B pairs are formed upon the dissociation of Fe _i –V pairs during the lifetime of the Mössbauer state (T _1/2?=?100 ns). The resulting free interstitial Fe_i diffuses over sufficiently large distances during the lifetime of the Mössbauer state to encounter a substitutional B impurity atom, forming Fe _i –B pairs, which are stable up to ～1,050 K on that time scale.     

Enhanced photoinduced desorption from metal nanoparticles by photoexcitation of confined hot electrons using femtosecond laser pulses

Strong fluence dependence of photodesorption cross sections is observed in femtosecond laser photodesorption of NO from (NO)2 on silver nanoparticles, in contrast to femtosecond photodesorption on bulk metals. The time scale of excitation buildup is found to be equal or less than the pulse duration of ～100 fs; NO translational energies are independent of fluence and pulse duration. We propose a nanoparticle-specific nonlinear mechanism in which, due to confinement, strongly nonthermal hot-electron distributions are maintained during the femtosecond pulses, enhancing the normal desorption pathway.     

Neutron depolarisation imaging: Stress measurements by magnetostriction effects in Ni foils

In this article we present first proof-of-principle neutron depolarization imaging measurements on Ni foils under mechanical stress. The magnetostrictive effect in Ni leads to a reorientation of the magnetic domains in the material depending on the applied force. This in turn leads to a change of the depolarization a neutron beam suffers from transmission of the sample. We propose to use this method as a new technique for the spatially resolved measurement of mechanical stress.     

Hypernuclear fine structure in (9)(lambda)Be

With a germanium detector array (Hyperball), we observed two gamma-ray peaks corresponding to the two transitions (5/2(+)-->1/2(+) and 3/2(+)-->1/2(+)) in the (9)(Lambda)Be hypernucleus which was produced by the 9Be(K-,pi(-)) reaction. The energies of the gamma rays are 3029 +/- 2 +/- 1 keV and 3060 +/- 2 +/- 1 keV. The energy difference was measured to be 31.4(+2.5)(-3.6) keV, which indicates a very small Lambda-spin-dependent spin-orbit force between a Lambda and a nucleon. This is the smallest level splitting by far ever measured in a hypernucleus.     

Near- and mid-infrared laser-optical sensors for gas analysis

Semiconductor diode lasers were first developed in the mid-1960s and found immediate application as much needed tunable sources for high-resolution laser spectroscopy commonly referred to as tunable diode laser absorption spectroscopy (TDLAS). In this paper, currently available semiconductor lasers for spectroscopy in the near- and mid-infrared spectral region based upon gallium arsenide, indium phosphite, antimonides and lead-salt containing compounds will be reviewed together with the main features of TDLAS. Room-temperature measurements of atmospheric carbon dioxide near 2 μm will be discussed and recent results obtained with a fast chemical sensor for methane flux measurements based on lead-salt diode lasers operating near 7.8 μm will be presented.     

Magnetic Properties of Nanoparticles of Antiferromagnetic Materials

Hyperfine Interactions - The magnetic properties of antiferromagnetic nanoparticles have been studied by Mössbauer spectroscopy and neutron scattering. Temperature series of Mössbauer...