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141.
G. Stancari S. N. Atutov R. Calabrese L. Corradi A. Dainelli C. de Mauro A. Khanbekyan E. Mariotti P. Minguzzi L. Moi S. Sanguinetti L. Tomassetti S. Veronesi 《The European physical journal. Special topics》2007,150(1):389-392
Francium is one of the best candidates for atomic parity
nonconservation (APNC) and for the search of permanent electric
dipole moments (EDMs). APNC measurements test the weak force
between electrons and nucleons at very low momentum transfers. They
also represent a unique way to detect weak nucleon-nucleon
interactions. EDMs are instead related to the time-reversal
symmetry. Preliminary to these fundamental measurements are
precision studies in atomic spectroscopy and the development of
magneto-optical traps (MOT), which partially compensate for the lack
of stable Fr isotopes. At LNL Legnaro, francium is produced by
fusion of 100-MeV 18O with 197Au in a thick target,
followed by evaporation of neutrons from the compound nucleus.
Francium diffuses inside the hot target (1200 K) and is surface
ionized for injection at 3 keV in an electrostatic beamline.
Typically, we produce 1×106 (210Fr ions)/s for a
primary flux of 1.5×1012 particles/s. We have studied
Fr yields as a function of primary beam energy, intensity, and
target temperature. Information on the efficiency of bulk
diffusion, surface desorption and ionization is deduced. The beam
then enters a Dryfilm-coated cell, where it is neutralized on a
heated yttrium plate. The escape time of neutral Fr (diffusion +
desorption) is approximately 20 s at 950 K, as measured with a
dedicated setup. In the MOT, we use 6 orthogonal Ti:sapphire laser
beams for the main pumping transition and 6 beams from a stabilized
diode repumper. Fluorescence from trapped atoms is observed with a
cooled CCD camera, in order to reach noise levels from stray
light equivalent to approximately 50 atoms. Systematic tests are
being done to improve the trapping efficiency. We plan to further
develop Fr traps at LNL; in parallel, we will study APNC and EDM
techniques and systematics with stable alkalis at Pisa, Siena, and
Ferrara. 相似文献
142.
143.
Synthesis and characterization of CdS nanoparticles embedded in a polymethylmethacrylate matrix 总被引:3,自引:0,他引:3
Pedone L Caponetti E Leone M Militello V Pantò V Polizzi S Saladino ML 《Journal of colloid and interface science》2005,284(2):495-500
CdS nanopowder capped with sodium bis(2-ethylhexyl)sulfosuccinate was synthesized by using water-in-oil microemulsions. The CdS nanoparticles of about 5 nm obtained were embedded in polymethylmethacrylate matrix by a photocuring process. The transparent yellow solid compound was characterized by optical absorption and emission spectroscopy, high-resolution transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The properties of this compound were compared with those of the nanopowder dispersed in heptane and in methylmethacrylate. The results obtained indicate that the nanoparticles are homogeneously dispersed in the matrix and do not change in size during the embedding process. Even if the surface slightly changes its luminescence properties, as a consequence of the different new chemical environment, the final product seems to be suitable for practical applications. 相似文献
144.
D. Ackermann S. Antalic M. Axiotis D. Bazzacco S. Beghini G. Berek L. Corradi G. De Angelis E. Farnea A. Gadea F. P. Heßberger S. Hofmann M. G. Itkis G. N. Kniajeva E. M. Kozulin A. Latina T. Martinez R. Menegazzo G. Montagnoli G. Münzenberg Yu. Ts. Oganessian C. Rossi-Alvarez M. Ruan R. N. Sagaidak F. Scarlassara A. M. Stefanini S. Szilner M. Trotta C. Ur 《The European Physical Journal A - Hadrons and Nuclei》2003,20(1):151-152
To study basic properties of the fusion reaction dynamics for heavy compound systems the partial-wave distribution
can be employed as an alternative to the classically used fusion/fission excitation functions. A variety of reactions leading to compound nuclei (CN) in the Pb region can be used to investigate features like the fusion-fission competition, the role of deformation in the fusion of heavy systems and a possible effect of the Z = 82 shell on the enhancement of evaporation residue (ER) production.Received: 5 November 2002, Revised: 26 March 2003, Published online: 9 March 2004PACS:
24.75. + i General properties of fission - 25.70.Gh Compound nucleus - 25.70.Jj Fusion and fusion-fission reactions 相似文献
145.
H. Pedersen S. Leone A. Henry V. Darakchieva P. Carlsson A. Gällström E. Janzén 《固体物理学:研究快报》2008,2(4):188-190
200 µm thick 4H‐SiC epilayers have been grown by chloride‐based chemical‐vapor deposition using methyltrichlorosilane (MTS) as single precursor. The very high crystalline quality of the grown epilayer is demonstrated by high resolution X‐Ray Diffraction rocking curve with a full‐width‐half‐maximum value of only 9 arcsec. The high quality of the epilayer is further shown by low temperature photoluminescence showing strong free exciton and nitrogen bound exciton lines. The very high crystalline quality achieved for the thick epilayer grown in just two hours at 1600 °C suggests that MTS is a suitable precursor molecule for SiC bulk growth. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
146.
A parallel successive overrelaxation (SOR) method is proposed for the solution of the fundamental symmetric linear complementarity problem. Convergence is established under a relaxation factor which approaches the classical value of 2 for a loosely coupled problem. The parallel SOR approach is then applied to solve the symmetric linear complementarity problem associated with the least norm solution of a linear program.This work was sponsored by the United States Army under Contract No. DAAG29-80-C-0041. This material is based on research sponsored by National Science Foundation Grant DCR-84-20963 and Air Force Office of Scientific Research Grants AFOSR-ISSA-85-00080 and AFOSR-86-0172.on leave from CRAI, Rende, Cosenza, Italy. 相似文献
147.
A new technique is presented to study translation-to-vibrational (T—V) energy transfer and translationally enhanced reactive events. The method utilizes excimer laser photolysis to produce translationally “hot” atoms and time-resolved infrared detection of specific excited states. 相似文献
148.
149.
Grippa E Gatto MT Leone MG Tita B Adbel-Haq H Vitalone A Silvestrini B Saso L 《Biomedical chromatography : BMC》2001,15(1):1-8
A HPLC method for the determination of lonidamine in serum and testis, suitable for pharmacological studies in the rat and other mammals, has been developed. Briefly, 0.5 mL of serum or about 0.2 g of testicular tissue were extracted with ethyl acetate and evaporated to dryness under nitrogen. The residue was redissolved in methanol and an aliquot was injected onto a C18 column eluted with a mobile phase consisting of acetonitrile:water (51:49, v/v), containing 0.1% trifluoroacetic acid. The eluate was monitored at 230 nm with a sensitivity of 0.05 AUFS. By this method, the pharmacokinetics and the serum and testicular levels of the drug up to 120 h after the administration of one single dose (100 mg/kg body weight) of lonidamine to Sprague-Dawley rats have been studied. Results were highly variable, as previously reported, but a very good linear correlation was found between the serum and the testicular levels, suggesting that, in the rat, and possibly in the human, testicular levels could be estimated based on the serum concentrations. 相似文献
150.