Recommissioning the Modernized VEPP-2000 Electron–Positron Collider

The VEPP-2000 electron–positron collider has been operating at the Budker Institute of Nuclear Physics (BINP) since 2010. Applying the concept of round colliding beams allowed the record value of the beam–beam parameter ξ ～ 0.12 to be reached. The upgrading of the VEPP-2000 complex, including the connection to the new BINP Injection Complex and modification of the electron–position booster and the BEP–VEPP-2000 transfer channels to work at 1 GeV, resulted in a significant increase in luminosity. Work on statistical data collection using detectors is in progress.     

Mobility of charge carriers in porous silicon layers

The (conduction) mobility of majority charge carriers in porous silicon layers of the n and p types is estimated by joint measurements of electrical conductivity and free charge carrier concentration, which is determined from IR absorption spectra. Adsorption of donor and acceptor molecules leading to a change in local electric fields in the structure is used to identify the processes controlling the mobility in porous silicon. It is found that adsorption of acceptor and donor molecules at porous silicon of the p and n types, respectively, leads to a strong increase in electrical conductivity, which is associated with an increase in the concentration of free carrier as well as in their mobility. The increase in the mobility of charge carriers as a result of adsorption indicates the key role of potential barriers at the boundaries of silicon nanocrystals and may be due to a decrease in the barrier height as a result of adsorption.     

Photoluminescence properties of silicon nanocrystals grown by nanosecond laser ablation of solid-state targets in an inert gas atmosphere

It was found that the photoluminescence intensity decay kinetics of nanocrystalline silicon layers formed by nanosecond laser ablation of crystalline silicon targets in a helium atmosphere exhibit a power-law behavior with an exponent from 0.9 to 1.5, depending on the temperature and luminescence photon energy in the range of 1.4–1.8 eV, which indicates photoexcited carrier recombination controlled by dissipative tunneling processes in silicon nanocrystal ensembles in a suboxide matrix.     

The accommodation of the translational and rotational energy of a gas in a Knudsen flow past a thin wire

The paper presents the results obtained in determining the accommodation coefficients for the translational and rotational energy of gas molecules in a Knudsen flow past a thin wire. The method used was based on numerically solving the complete heat balance equation for a wire probe. The accommodation coefficients were determined for H₂, N₂, CH₄, and CO₂ on a gilded tungsten surface. For hydrogen with a quenched rotational energy, a negative accommodation coefficient of rotational energy was obtained due to the conversion of the rotational energy of incident molecules into the translational energy of reflected molecules.     

Investigation of the mechanism of fragment coordination of aromatic molecules with transition metals by photoelectron spectroscopy-tricarbonyliron complexes

Conclusions The changes in the chemical shifts of organic molecules during complex formation are well known in organometallic chemistry [24]. Thus, coordinated dienes lose the olefinic characteristics; they are not hydrogenated, do not enter into the Diels-Alder reaction, and react with electrophilic reagents. At the present time the search for a link between the structure of organometallic complexes in terms of rigorous quantum-chemical calculations is beginning. The construction of experimentally substantiated models which make it possible to explain qualitatively the marked changes in the characteristics of organic compounds in the presence of the atoms of transition metals is therefore essential for a deeper understanding of the orbital mechanisms lying at the basis of catalysis.The PE spectra were measured on an ÉS 3201 electron spectrometer with an inlet system heated to 200°C. The resolution, determined from the width of the²P_3/2Xe band at the half-height, amounted to 40 meV. Compounds (II) and (III) were obtained by the previously described methods [25, 26], and the analytically pure substances were used for the investigation.Scientific-Research Institute of Physics, A. A. Zhdanov Leningrad State University. A. N. Nesmeyanov Institute of Heteroorganic Compounds, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 27, No. 3, pp. 69–75, May–June, 1986.     

Reaction of αH,αH,ωH-Perfluoroalkyl Benzyl Sulfones with Compounds Having an Active Methylene Group

Russian Journal of Organic Chemistry -     

On Some Elementary Properties of Soluble Groups of Derived Length 2

Conditions are found for a soluble group of derived length 2 with few relations to be universally equivalent to a free soluble group of derived length 2. The Fitting radical of a soluble group of derived length 2 with few relations coincides with the derived subgroup. Also, if an n-generator soluble group is elementarily equivalent to a free soluble group of rank m and derived length k then for k=2 or k>2 and n=m the groups are isomorphic.