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Total Reaction Cross Section Measurements at Intermediate
Energy for Proton-Halo Candidate 23Al and Its Neighbours
CAI Xiang-Zhou, SHEN Wen-Qing, , FENG Jun, FANG De-Qing, ZHU Zhi-Yuan, JIANG Wei-Zhou, MA Yu-Gang, ZHANG Hu-Yong, ZHONG Chen, YU Li-Ping, ZHAN Wen-Long, GUO Zhong-Yan, XIAO Guo-Qing, WANG Jian-Song, ZHU Yong-Tai, WANG Jin-Chuan, LI Jia-Xing, WANG
Meng, WANG Jian-Feng, NING Zhen-Jiang, WANG Quan-Jin, CHEN Zhi-Qiang
Chin. Phys. Lett. 2001, 18 (9):
1189-1191
.
Total reaction cross sections σR for some proton-rich isotones (N = 10) near 23Al on a carbon target have been measured at intermediate energies in the experiment performed at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou. The Z-dependence of σR shows a remarkable enhancement for 23Al relative to its neighbours. The difference factor d has been deduced from the measured σR by using the Glauber or Boltzmann-Uehling-Uhlenbeck models. From the above analysis, a possible one-proton halo structure is suggested for 23Al.
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Nearly-Noncritical Phase Matching in MgO:LiNbO3 Optical Parametric Oscillator
YAO Jian-Quan, YU Yi-Zhong, WANG Peng, WANG Tao, ZHANG Bai-Gang, DING Xin, CHEN Ji, H. J. Peng, H. S. Kwok
Chin. Phys. Lett. 2001, 18 (9):
1214-1217
.
We have proposed and demonstrated a nearly-noncritical
phase-matched (NCPM) optical parametric oscillation (OPO) in an MgO: LiNbO3 crystal with 5-mol% MgO by temperature tuning. By giving up perfect NCPM, the practical tuning range for the OPO is increased by two times. For the crystal, the operated temperature decreases with the phase-matching angle at degeneracy. With a cutting angle of 82°instead of the noncritical case of 90°, the tuning range was increased. In order to obtain sufficiently high output pulse energy for both signal and idler throughout the entire tuning range, five sets of mirrors were used for the resonator. The tuning range of the OPO was 800-1700 nm with temperatures tuning from 83°C to 224.2°C. The output energy was about 6.45 mJ with a conversion efficiency of nearly 13%. The bandwidth of the output was 1.0-1.1 nm.
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Theoretical Scanning Tunneling Microscopy Images of Metal
(Fe, Co, Ni, and Cu) Phthalocyanines
LI Qun-Xiang, YANG Jin-Long, YUAN Lan-Feng, HOU Jian-Guo, ZHU Qing-Shi
Chin. Phys. Lett. 2001, 18 (9):
1234-1236
.
The scanning tunneling microscopy (STM) images of isolated iron
phthalocyanine (FePc), cobalt phthalocyanine (CoPc), nickel
phthalocyanine (NiPc) and copper phthalocyanine (CuPc) are simulated theoretically. All the simulated STM images show submolecular structures and reproduce well the features of the experimental images. The results show that there is a strong dependence of the STM images on the ion valence configuration of the metal ion. At the small tip bias voltages of less than 0.5 V, the central metal ions in NiPc and CuPc appear as holes in the molecular images, while they are the highlighted bumps in FePc and CoPc. The simulated images are interpreted by the fact that both FePc and CoPc systems have significant dz2 character near the Fermi level while the NiPc and CuPc systems do not. Moreover, we predict that the central nickel ion for NiPc appears a highlighted point when the tip bias voltage is larger than 0.7 V.
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Interlayer Segregation of Cu Atoms in Metal Multilayers
YU Guang-Hua, LI Ming-Hua, ZHU Feng-Wu, JIANG Hong-Wei, LAI Wu-Yan, CHAI Chun-Lin
Chin. Phys. Lett. 2001, 18 (9):
1245-1248
.
The experimental results show that the exchange coupling field Hex of NiFe/FeMn for Ta/NiFe/FeMn/Ta multilayers is higher than that for the spin valve multilayers Ta/NiFe/Cu/NiFe/FeMn/Ta. The composition and chemical states at the surface of Ta(12 nm)/NiFe(7 nm), Ta(12 nm)/NiFe(7 nm)/Cu(4 nm) and Ta(12 nm)/NiFe(7 nm)/ Cu(3 nm)/NiFe(5 nm) were studied by using the x-ray photoelectron spectroscopy. The results show that no element from the underlayers floats out or segregate to the surface for Ta(12 nm)/NiFe(7 nm), Ta(12 nm)/NiFe(7 nm)/ Cu(4 nm). However, Cu atoms segregate to the surface of Ta(12 nm)/NiFe(7 nm)/Cu(3 nm)/NiFe(5 nm) multilayers, i.e. to the NiFe/FeMn interface for Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers. The authors believe that the presence of Cu atoms at the interface of NiFe/FeMn is one of the important factors which will cause the exchange coupling field Hex of Ta/NiFe/FeMn/Ta multilayers to be higher than that of Ta/NiFe/Cu/NiFe/FeMn/Ta multilayers.
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GaInNAs/GaAs Multiple-Quantum Well Resonant-Cavity-Enhanced Photodetectors at 1.3 μm
PAN Zhong, LI Lian-He, XU Ying-Qiang, ZHANG Wei, LIN Yao-Wang, ZHANG Rui-Kang, ZHONG Yuan, REN Xiao-Min
Chin. Phys. Lett. 2001, 18 (9):
1249-1251
.
A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced photodetector (RCE-PD) operated at wavelength of 1.3 μm with the full-width at half-maximum of 4 nm was demonstrated. The GaInNAs RCE-PD was grown by molecular-beam epitaxy using a home-made ion-removed dc-plasma cell as nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature, which is very beneficial for applications in long-wavelength absorption devices. For a 100 μm diameter RCE-PD, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is -18 V. The measured 3dB bandwidth is 308 MHz, which is limited by the resistance of p-type distributed Bragg reflector mirror. The tunable wavelength in a range of 18 nm with the angle of incident light was observed.
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Dielectric Characteristics and Layer Periodic Effects of Ferroelectric Superlattice BaTiO3/SrTiO3
ZHANG Jiang, YIN Zhen, ZHANG Ming-Sheng, CHEN Wan-Chun
Chin. Phys. Lett. 2001, 18 (9):
1271-1274
.
A pseudospin-phonon coupled model in double-time Green's function theory has been developed to investigate dielectric susceptibility of the ferroelectric-dielectric superlattice BaTiO3/SrTiO3(BTO/STO). As the pseudospin-pseudospin interaction and the pseudospin-phonon interactions increase, the dielectric susceptibility changes from narrow shape into the strong-broad shape with the peak shift to higher temperature region. With increasing pseudospin-phonon interaction in the BTO layer and at small pseudospin-pseudospin interaction in BTO layer, the dielectric susceptibility was sensitively adjusted around the transition temperature of strontium titanate, and at large pseudospin-pseudospin interaction in the BTO layer, the dielectric susceptibility was increased in high temperature region covering the tetragonal-cubic transition temperature of barium titanate. A critical period of 10/10 in the BTO/STO superlattice has been obtained, which is in good agreement with experimental data of 40Å, for ten unit cells.
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Preparation of AlN Films by Ion-Beam-Enhanced Deposition
MEN Chuan-Ling, XU Zheng, ZHENG Zhi-Hong, DUO Xin-Zhong, ZHANG Miao, LIN Cheng-Lu
Chin. Phys. Lett. 2001, 18 (9):
1282-1284
.
Aluminum nitride (AlN) films have been synthesized on Si(100)
substrates by ion-beam-enhanced deposition. Spreading resistance profile results suggest that the spreading resistance decreases with increasing rates of Al evaporation. If the evaporation rate of Al is higher than 2.5Å/s, the quality of AlN film will greatly deteriorate. The spreading resistance of the best quality film deposited at 0.5Å/s rate of Al was larger than 108Ω. X-ray photoelectron spectroscopy measurements indicate the formation of AlN films at 0.5 and 1.0Å/s evaporation rate of Al. With the increasing evaporation rate of Al, the ratio of N to Al is decreased. When deposited at 0.5 and 1.0Å/s evaporation rates of Al, the ratio of N to Al was 0.402:1 and 0.250:1, respectively. Atomic force microscopy observation also exhibits that the surface of the AlN film formed at 0.5Å/s rate is smoother and more uniform than that formed at 1.0Å/s.
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45 articles
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