Chemical effects of photonuclear reactions in the propyl bromides

When nuclear reactions occur in atoms in molecules chemical changes follow as a result of the recoil of the product atoms. The nature of these chemical changes has been studied intensively for a number of systems but in most cases the magnitude of the recoil energy has been about the same. In the present studies use was made of a much greater recoil energy than that normally used. The reaction Br(γ,η)Br* gives a recoil bromine2 atom with an energy of the order 105ev, compared to 102ev for the product of the Br(η,γ)Br* reaction which is usually used

The effect of oxygen on the recoil reactions of carbon-11 in hydrocarbons

The recoil reactions of carbon-11 produced by the c 12 (y, n)C11 reaction in benzene, cyclohexane, and n-hexane have been studied. Using gas chromatography for the analysis, the yields of carbon-11 labeled methane, ethane, ethylene, and acetylene were determined. The effect of radiation dose and oxygen scavenger on these yields was investigated

Growth and characterization of multiferroic BiMnO3_3 thin films

We have grown epitaxial thin films of multiferroic BiMnO$_3$ using pulsed laser deposition. The films were grown on SrTiO$_3$ (001) substrates by ablating a Bi-rich target. Using x-ray diffraction we confirmed that the films were epitaxial and the stoichiometry of the films was confirmed using Auger electron spectroscopy. The films have a ferromagnetic Curie temperature ($T_C$) of 85$\pm$5 K and a saturation magnetization of 1 $\mu_B$/Mn. The electric polarization as a function of electric field ($P-E$) was measured using an interdigital capacitance geometry. The $P-E$ plot shows a clear hysteresis that confirms the multiferroic nature of the thin films.Comment: 4 pages, 4 figures, submitted to J. Appl. Phy

Photoproduction of calcium-47*

The irradiation of highly enriched Ca 48co3 with a bremsstrahlung beam of maximum energy 46 Mev produced Ca47 with a yield of 1. 1 to 3 . O uc/mg Ca48 at half-saturation. The half-life of a sample measured through aluminum absorber to eliminate the contribution by the sc47 daughter was 4. 51 ±. 0 . 02 days . By comparison with the Cu63( 7, n)Cu62 reaction the integrated cross section from 0 to 46 Mev for the sum of the reactions ca48( 7, n)Ca47 and Ca48( 7\u27, p)K47 was calculated to be 29 Mev-mbarn. The Ca46 content of the sample calculated to the end of the bombardment was,.. 0. 040/o, probably the result of the Ca 48 ( ?\u27, 3n) and ( 7, p2n) reactions

High pressure Ca-VI phase between 158-180 GPa: Stability, electronic structure and superconductivity

We have performed ab initio calculations for new high-pressure phase of Ca-VI between 158-180 GPa. The study includes elastic parameters of mono- and poly-crystalline aggregates, electronic band structure, lattice dynamics and superconductivity. The calculations show that the orthorhombic Pnma structure is mechanically and dynamically stable in the pressure range studied. The structure is superconducting in the entire pressure range and the calculated Tc (~25K) is maximum at ~172 GPa, where the transfer of charges from 4s to 3d may be thought to be completed.Comment: 8 pages, 4 figures; PACS number(s): 74.70.Ad, 62.20.de, 71.20.-b, 74.20.Pq, 74.25.Kc, 74.62.Fj; Keywords: Calcium; High pressure; Electronic band structure; Phonon spectrum; Elastic constants; Superconducto

continuum modelling of semiconductor heteroepitaxy an applied perspective

Semiconductor heteroepitaxy involves a wealth of qualitatively different, competing phenomena. Examples include three-dimensional island formation, injection of dislocations, mixing between film and substrate atoms. Their relative importance depends on the specific growth conditions, giving rise to a very complex scenario. The need for an optimal control over heteroepitaxial films and/or nanostructures is widespread: semiconductor epitaxy by molecular beam epitaxy or chemical vapour deposition is nowadays exploited also in industrial environments. Simulation models can be precious in limiting the parameter space to be sampled while aiming at films/nanostructures with the desired properties. In order to be appealing (and useful) to an applied audience, such models must yield predictions directly comparable with experimental data. This implies matching typical time scales and sizes, while offering a satisfactory description of the main physical driving forces. It is the aim of the present review to show tha..

The J_1-J_2 antiferromagnet with Dzyaloshinskii-Moriya interaction on the square lattice: An exact diagonalization study

We examine the influence of an anisotropic interaction term of Dzyaloshinskii-Moriya (DM) type on the groundstate ordering of the J_1-J_2 spin-1/2-Heisenberg antiferromagnet on the square lattice. For the DM term we consider several symmetries corresponding to different crystal structures. For the pure J_1-J_2 model there are strong indications for a quantum spin liquid in the region of 0.4 < J_2/J_1 < 0.65. We find that a DM interaction influences the breakdown of the conventional antiferromagnetic order by i) shifting the spin liquid region, ii) changing the isotropic character of the groundstate towards anisotropic correlations and iii) creating for certain symmetries a net ferromagnetic moment.Comment: 7 pages, RevTeX, 6 ps-figures, to appear in J. Phys.: Cond. Ma

Lifetime measurement of the metastable 3d 2D5/2 state in the 40Ca+ ion using the shelving technique on a few-ion string

We present a measurement of the lifetime of the metastable 3d 2D5/2 state in the 40Ca+ ion, using the so-called shelving technique on a string of five Doppler laser-cooled ions in a linear Paul trap. A detailed account of the data analysis is given, and systematic effects due to unwanted excitation processes and collisions with background gas atoms are discussed and estimated. From a total of 6805 shelving events, we obtain a lifetime tau=1149+/-14(stat.)+/-4(sys.)ms, a result which is in agreement with the most recent measurements.Comment: 10 pages, 7 figures. Submitted for publicatio