Application of Q-band electron spin echo spectrometer to investigation of glasses doped with rare earth ions

The Q-band electron spin echo (ESE) spectrometer which was created using modern microwave components is described. This simple incoherent apparatus was used with the X-band one for the study of phosphate and silicate glasses doped with non-Kramers rare earth Tb³⁺ ions. the EPR spectra measured by the ESE method have frequency independent peaks. The experimental results presumably show the existence of several types of paramagnetic centers in studied systems.     

Resonance effects in a phased antenna array constructed from rectangular waveguides

Translated from Matematicheskie Modeli i Optimizatsiya Vychislitel'nykh Algoritmov, pp. 131–143, 1993.     

Determination of tributyltin oxide in coastal marine sediments and mussels by electrothermal atomic absorption spectrometry

We have devised a new method for bis(tributyltin)oxide (TBTO) determination in marine sediments and mussels. This technique involves an n-hexane/methylene chloride mixture extraction and extract purification with a sodium hydroxide wash in order to eliminate interfering compounds. TBTO is then extracted again by nitric acid and converted into an inorganic tin species; the analysis has been effected using Zeeman graphite furnace-atomic absorption spectrophotometry. The method detection limit for the matrices examined is 0.004 μg TBTO g^?1 (wet weight) and is sufficient for the analysis in real samples. The percentage recovery of TBTO from sediments and mussels samples is higher than 85% and 95% respectively. This method has been applied to TBTO level determination in sediments and mussels (Mytilus galloprovincialis) sampled in the harbour area in Taranto, where mussel culture activities are much developed; the TBTO levels obtained in sediments and mussels were in the range 15-47 ng g^?1 (wet weight) and 11-30 ng g^?1 (wet weight) respectively. Such values are comparable with those found in other harbour areas in the Mediterranean Sea.     

Certification of the sulphur content of three rapeseed reference materials

Summary The sulphur content of three rapeseed reference materials has been certified on the basis of measurements made by inductively coupled plasma-optical emission spectroscopy, isotope-dilution mass spectrometry and ion chromatography. Their suitability for the calibration of x-ray fluorescence spectrometers used for measuring sulphur in rapeseed samples was established.     

Line Narrowing of a Tunable High Pressure CO2 Laser by Means of an Improved Non-Littrow Cavity

A model is reported to foresee ,for different mirror choices, the spectral properties of a high pressure, frequency tunable, CO₂ laser, operating with a non-Littrow grating mounting. The calculations show a larger frequency selectivity for not collimated plane cavities. The model is experimentally verified in a suitable high pressure laser. In particular narrowed linewidths less than 300MHz ( FWHM) are obtained.     

Arc erosion reduction on electrical contacts using transversecurrent injection

Electrical contact lifetime is often directly determined by arc erosion. A method for reducing are erosion was developed consisting of injecting from an external current source an additional electrical current flowing parallel to the contact surface. This method was examined in three are environments using the additional transverse electrical current with a density less than 1 A/mm²: 1) automobile ignition contacts; 2) pulsed air arc; and 3) low pressure (P=100 mTorr) arc in nitrogen, SEM and X-ray examination showed that application of a transverse current in a contact during arcing changed the phase composition and microstructure of the contact surface. Under optimal conditions, the microstructure which is formed is significantly more erosion resistant than without the transverse current injection     

Gain saturation in quantum-well heterostructures

The effect of radiation gain saturation in quantum-well heretostructures was investigated in the system GaAs—AlGaAs with regard to the spectral line broadening and the type of radiation polarization. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 797–800, November–December, 1997.     

Electronic structure of the antiferromagnetic phase of NiMn

We present for the first time a self-consistent calculation of the electronic energy band structure of NiMn in the antiferromagnetic tetragonal phase. The electronic energy spectrum is calculated, along with the full and partial electronic density of states, the Fermi surface, the electronic specific heat coefficient, and the magnetic moments on each type of atom. We have studied the influence of structural distortions and antiferromagnetic ordering on the electronic structure of NiMn. Satisfactory agreement is found with the existing experimental data.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 18–23, August, 1991.The authors express their appreciation to N. I. Kulikov and A. F. Tatarchenko for assistance in the computer calculations and for useful discussion of the work.     

Magnetism in disordered magnetic Fe82−xNixCr18

The zero field μSR-method has been used to study the magnetism in the disordered magnetic alloy Fe_82−xNi_xCr₁₈ near the three-critical, pointx=25. The dynamic and static local field distributions are analyzed. The difference between spin-glass states obtained either from the paramagnetic or after the double transition is discussed.