| 1. |
- Lumpkin, A. H., et al.
(författare)
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Evidence for microbunching "sidebands" in a saturated free-electron laser using coherent optical transition radiation
- 2002
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Ingår i: Physical Review Letters. - 1079-7114. ; 88:23, s. 4-4
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Tidskriftsartikel (refereegranskat)abstract
- We report the first measurements of z -dependent coherent optical transition radiation (COTR) due to electron-beam microbunching at high gains (>10(4) ) including saturation of a self-amplified spontaneous emission free-electron laser (FEL). In these experiments the fundamental wavelength was near 530 nm, and the COTR spectra exhibit the transition from simple spectra to complex spectra (5% spectral width) after saturation. The COTR intensity growth and angular distribution data are reported as well as the evidence for transverse spectral dependencies and an "effective" core of the beam being involved in microbunching.
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| 2. |
- Borge, M. J. G., et al.
(författare)
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Beta-delayed multiparticle emission studies at ISOL-type facilities
- 2004
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 746, s. 243-243
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Konferensbidrag (refereegranskat)abstract
- We report here on the recent beta-decay studies made at ISOL-type Facilities to determine the multiparticle breakup mechanism of excited states in light nuclei by studying them in full kinematics. In particular the results obtained for the A = 9 isobars and the breakup of the 12.7 MeV state in C-12 of unnatural parity are discussed. The breakup of the latter has been debated since more than a decade. Mirror beta transitions in the A = 9 chain are compared and a large asymmetry factor is deduced for the transitions to high excitation energy in Be-9 (11.8 MeV) and B-9 (12.2 MeV) fed in the beta-decay of Li-9 and C-9 respectively. It is shown that the asymmetry is not due to experimental problems or differences in the mechanisms of breakup or in the spin of the states. As no asymmetry is found in the gs to gs transition it must be due to the particular structure of these excited states. The controversy on the breakup mechanism of the 12.7 MeV state is resolved.
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| 3. |
- Huang, D. G., et al.
(författare)
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Synthesis, structural characterizations and magnetic properties of a series of mono-, di- and polynuclear manganese pyridinecarboxylate compounds
- 2004
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :7, s. 1454-1464
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Tidskriftsartikel (refereegranskat)abstract
- Seven new manganese(II, III, IV) pyridinecarboxylate compounds (Et4N)[MnCl2(pic)(2)] (1, Hpic = picolinic acid) [MnCl(Pic)(2)(H2O)].H2O (2), [MnCl(pic)(H2O)2](n) (3), [Mn(Pic)(2)](n) (4), [MnCl(pic)](n) (5), [MnCl2(4-C5H4NHCOO)](n) (6) and [Mn2O2(pic)(4)] (7) were synthesized and structurally characterized. The picolinate ligand coordinates to the Mn ion forming a chelating five-membered ring which constructs diverse architectures by various bridging modes, such as mu-Cl, mu(1,1)(-) and mu(1,3)-carboxylate bridges (syn-syn and syn-anti modes). The interaction between the pyridyl rings is discussed, displaying a face-to-face pi-pi stacking for complex 6 and a T-shaped C-H...pi attraction for complex 4. Complex 3 has an infinite zigzag chain structure in which two neighboring Mn ions are linked by a carboxylate bridge in a syn-anti mode. In complex 4, the Mn(pic)(2) fragments are joined to each other by double mu(1,1)-carboxylate bridges, forming a 2D layer structure. Complex 5 contains Mn4O4 square subunits which are connected by double mu-Cl bridges to form a grid-like 2D structure. The isonicotinate complex 6 has a zigzag chain structure containing mixed double mu-Cl and mu(1,3)-carboxylate bridges in a syn-syn mode. Protonation at the pyridyl-N position was found and identified by the IR and magnetic properties of 6. The participation of an oxidizing agent like MnO4- leads to complexes containing higher valent manganese (1, 2 and 7). The IR spectra of these complexes are discussed and found to be consistent with the structural features. The magnetic properties of complexes 4, 5 and 6 have been investigated. Antiferromagnetic coupling interactions were observed and satisfactory fitting results were obtained with J values ranging from -0.63 cm(-1) to -2.35 cm(-1). The magnetic parameters of these complexes, together with the parameters of other Mn complexes with comparable structures, are compared and discussed based on the bridging modes. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).
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| 4. |
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| 5. |
- Wang, L. W., et al.
(författare)
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Investigation of damage behaviour and isolation effect of n-type 6H-SiC by implantation of oxygen
- 2000
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 33:12, s. 1551-1555
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide is an important wide-band-gap semiconductor for high temperature, high-voltage, high-power and high-frequency devices. Electrical isolation is an important aspect for device applications. In this report, oxygen ions, 70 keV with doses ranging from 5 x 10(13) to 5 x 10(15) cm(-2), have been implanted into n-type 6H-SiC to investigate the possibility of forming a high-resistive layer. The damage behaviour and internal stress were checked by Rutherford backscattering spectroscopy and channelling, and an x-ray rocking curve, respectively. Atomic force microscope observations revealed that the surface morphology is quite sensitive to the implantation even at a dose of 1 x 10(14) cm(-2) After annealing in nitrogen at 1200 degrees C, no remarkable damage recovery could be seen if the deposit damage energy is over the critical value. Schottky structures of Au/SiC have been fabricated on the annealed samples and I-V curves of metal/SiC/InGeNi were measured at room temperature at both forward and reverse bias; the electrical isolation effect was observed at proper implantation dosages. The results indicated that there exists a dose window for electrical isolation.
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| 6. |
- Wang, L. W., et al.
(författare)
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Structural and electrical characteristics of oxygen-implanted 6H-SiC
- 2000
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 169, s. 1-5
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Tidskriftsartikel (refereegranskat)abstract
- Silicon carbide is an important wide band gap semiconductor for high-temperature, high-voltage, high-power and high-frequency devices. Ion implantation is an important aspect for both fundamental research and device applications. In this report, oxygen ions, 70 keV with dose ranging from 5 x 10(13) to 5 x 10(15) cm(-2), have been implanted into n-type BH-SIC. The damage behavior and internal stress were checked by Rutherford backscattering spectroscopy and channeling and X-rays rocking curve, respectively. Atomic force microscope observations revealed that the surface morphology is quite sensitive to the implantation even at a dose of 1 x 10(14)/cm(-2). After annealing in nitrogen at 1200 degrees C, no remarkable damage recovery could be seen if the deposit damage energy is above the critical value. Schottky structures of Au/SiC have been fabricated and I-V curves of metal/SiC/InGeNi were measured at room temperature at both forward and reverse bias, electrical isolation effect was observed at proper implantation dose. The results indicated that there exists a dose window for electrical isolations. X-ray photoelectron spectroscopy (XPS) confirmed the formation of silicon oxide and CO due to oxygen implantation. In case of high-dose ion implantation, graphite phase was detected.
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