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Identification of Oblate Band in Odd-Odd 184Au
ZHANG Yu-Hu, WANG Hua-Lei, G. de Angelis, N. Marginean, A. Gadea, D. R. Napoli, M. Axiotis, C. Rusu, T. Martinez, ZHOU Xiao-Hong, GUO Wen-Tao, LIU Min-Liang, LEI Xiang-Guo, GUO Ying-Xiang, XU Fu-Rong
Chin. Phys. Lett. 2004, 21 (5):
799-801
.
High-spin states in 184Au have been populated via the 149Sm(29Si, 4nγ) 184Au reaction at a beam energy of 140 MeV. Three- or higher-fold γ-ray coincidences have been measured using the multidetector array of GASP. A rotational band built on the 11- oblate πh-111/2 vi-113/2 structure has been newly observed, similar to those reported in 186-194Au. This result extends the knowledge of shape coexistence to the currently lightest odd-odd Au isotope.
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In-Medium K+ and K- Production and K- Condensation in Supernova Matter
GUO Hua, ZHOU Ran, LIU Yu-Xin, , LIU Bo, LI Xi-Guo
Chin. Phys. Lett. 2004, 21 (5):
817-820
.
In-medium effects and neutrino trapping on K+ and K- production and K- condensation in supernova matter are investigated in a chiral hadronic model. Our results show that neutrino trapping shifts the critical density for K- condensation to higher density, the Q values for K+ and K- production are not sensitive to neutrino trapping, in-medium effects decrease the Q values for NN → NNK+K- and ΛN → NNK- and increase those for NN → NΛK+, K-p → Λπ0 and K-n → Λπ- as the density of supernova matter increases. Moreover, it is shown that neutrino trapping decreases the maximum masses of protoneutron stars compared with the neutrino-free case.
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Quantitative Single-Ion Irradiation by ASIPP Microbeam
WANG Xu-Fei, CHEN Lian-Yun, HU Zhi-Wen, WANG Xiao-Hua, ZHANG Jun, LI Jun, CHEN Bin, HU Su-Hua, SHI Zhong-Tao, WU Yu, XU Ming-Liang, WU Li-Jun, WANG Shao-Hu, YU Zeng-Liang
Chin. Phys. Lett. 2004, 21 (5):
821-824
.
A single-ion microbeam facility has been constructed by the microbeam research group in ASIPP (Institute of Plasma Physics, Chinese Academy of Science). The system was designed to deliver defined numbers of hydrogen ions produced by a van de Graaff accelerator, covering an energy range from 200 keV to 3 MeV, into living cells (5 μm-20 μm diameter) growing in culture on thin plastic films. The beam is collimated by a 1-μm inner diameter HPLC (high performance liquid chromatography) capillary, which forms the micron dimensional beam-line exit. A microbeam collimator, a scintillation ion counting system and a fast beam shutter, which constitute a precise dosage measuring and controlling system, jointly perform quantitative single-ion irradiation. With this facility, we can presently acquire ion-hitting efficiency close to 95%.
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Barrier Optical Waveguide Formation in La3Ga5SiO14 Crystals by High Energy Carbon Ion Implantation
WANG Xue-Lin, CHEN Feng, LU Fei, FU Gang, LI Shi-Ling, WANG Ke-Ming, ZHANG Huai-Jin, SHEN Ding-Yu, MA Hong-Ji, NIE Rui
Chin. Phys. Lett. 2004, 21 (5):
867-869
.
The barrier planar waveguides are fabricated for the first time in z-cut LGS (La3Ga5SiO14) crystals by 3.0 MeV and 6.0 MeV carbon ion implantations with dose of 2 x 1015ions/cm2 at room temperature. Four and six dark modes were observed by the prism-coupling method, respectively. The refractive index profiles were reconstructed by using the reflectivity calculation method. There are about 1.6% and 0.9% decreases at the optical barriers in the 3.0 MeV and 6.0 MeV cases, and the positions of the optical barriers are close to that of the damage peaks calculated by the TRIM'98 (Transport of Ions in Matter) code. It is found that the refractive index change may partly be due to the damage induced by the nuclear collision.
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Compression Behaviour and Equation of State of Zr44.4Nb7Cu13.5Ni10.8Be24.3 Bulk Metallic Glass up to 39 GPa
LI Gong, ZHAN Zai-Ji, WANG Li-Min, SUN Li-Ling, LIU Jing, WANG Wen-Kui,
Chin. Phys. Lett. 2004, 21 (5):
898-900
.
The compression of Zr44.4Nb7Cu13.5Ni10.8Be24.3 bulk metallic glass (BMG) is investigated at room temperature up to 39 GPa using in situ high-pressure energy dispersive x-ray diffraction with a synchrotron radiation source. The equation of state of the BMG is obtained by the calculation of the radial distribution function. Pressure-induced structural relaxation is exhibited. It is found that below about 6 GPa, the existence of excess free volume contributes to the rapid structural relaxation, which gives rise to rapid volumetric change, and the structural relaxation results in structural stiffness under higher pressure.
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Magnetointersubband Oscillations of the Two-Dimensional Electron Gas in AlxGa1-xN/GaN Heterostructures
JIANG Chun-Ping, YANG Fu-Hua, ZHENG Hou-Zhi, QIU Zhi-Jun, GUI Yong-Sheng, GUO Shao-Ling, CHU Jun-Hao, SHEN Bo, ZHENG You-Dou
Chin. Phys. Lett. 2004, 21 (5):
915-918
.
Shubnikov-de Haas (SdH) measurements are performed over a temperature range of 1.5-20 K in Al0.22Ga0.78N/GaN heterostructures with two subbands occupied. In addition to an intermodulation between two sets of SdH oscillations from the first and second subbands, a beating in oscillatory magnetoresistance at 12 K is observed, due to the mixing of the first subband SdH oscillations and `magnetointersubband' (MIS) oscillations. A phase shift of π between the SdH and MIS oscillations is also clearly identified. Our experimental results, i.e. that the SdH oscillations dominate at low temperature and MIS oscillations dominate at high temperature, fully comply with the expected behaviour of MIS oscillations.
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Pseudo-Spin-Valve Trilayer Using Amorphous CoNbZr Layer: Giant Magnetoresistance, Domain Structures and Potentials for Spin-Electronic Devices
WEN Qi-Ye, ZHANG Huai-Wu, JIANG Xiang-Dong, SHI Yu, TANG Xiao-Li, ZHANG Wan-Li
Chin. Phys. Lett. 2004, 21 (5):
941-944
.
We propose a pseudo-spin-valve (PSV) trilayer using amorphous CoNbZr alloy for soft magnetic layers. The giant magnetoresistance (GMR), domain structures and their variation upon thermal annealing are investigated. The GMR effect is not only stable up to 300°C but also enhanced due to the improvement of the interfaces between Cu and magnetic layers. With high annealing temperature, the magnetoresistance (MR) ratio decreases rapidly as a result of serious layer interdiffusion. Dense stripe domains, which disappear after annealing at 300°C for 1 h, are observed in the sandwiched films. It is found that after patterning to elliptic stripe with aspect ratio of 6:1, the trilayers have a single domain and their MR ratio increases. The dynamic MR behaviour under an ac magnetic field indicates that the patterned stripes have good linear MR responses. Therefore, it is believed that the CoNbZr/Cu/Co PSV trilayers have strong potentials for spin-electronic devices including magnetic random access memory.
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Structural and Magnetic Properties of FePt-C Nanocomposite Films
WANG Hao, YANG Fu-Jun, CHEN Kan-Song, ZHOU Bin, ZHANG Yuan-Wei, GU Hao-Shuang, CHIAH M. F., CHEUNG W. Y., WONG S. P
Chin. Phys. Lett. 2004, 21 (5):
949-951
.
Nanocomposite FePt-C thin films were prepared by a pulsed filtered vacuum arc deposition technique. The films were characterized by non-Rutherford backscattering spectrometry, x-ray diffraction, and magnetic force microscopy. The dependence of magnetic properties against annealing temperature was studied by using a vibrating sample magnetometer. Both x-ray diffraction and magnetic force microscopy analyses confirmed the formation of nano-crystallites of face-centred-tetragonal phase of FePt in the carbon matrix after annealing at a sufficiently high temperature. For the film with a composition of (Fe0.55Pt0.45)0.78C0.22, the coercivity and the grain size were observed to increase with increasing annealing temperature, up to a value of 3.5 kOe at an annealing temperature of 650°C, and with a grain size about 10.5 nm.
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Polarization of Hemicyanine Langmuir-Blodgett Films
LI Shu-Hong, MU Jian, WANG Wen-Jun, MA Shi-Hong, SUN Jing-Lan, CHU Jun-Hao, WANG Wen-Cheng
Chin. Phys. Lett. 2004, 21 (5):
952-954
.
The polarization dependence of electric field for hemicyanine layers deposited by the Langmuir-Blodgett (LB) technique has been measured. The experimental results show that ferroelectricity exists not only in thick films (200 nm) but also in thinner films (30 nm), and the remnant polarization is related to film thickness. In order to interpret the measured results, a planar rotor model was introduced, and a relation between polarization and film thickness was obtained by perturbation theory. The theory fitting agrees with experimental results well. It is confirmed that ferroelectricity in organic molecular LB films mainly arose from altering of molecular orientation.
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61 articles
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