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Thermal Entanglement in the Spin-S Heisenberg XYZ Model
LI Hu, LI Da-Chuang, WANG Xian-Ping, YANG Ming, CAO Zhuo-Liang
Chin. Phys. Lett. 2014, 31 (04):
040301
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DOI: 10.1088/0256-307X/31/4/040301
The thermal entanglement in the spin-S Heisenberg XYZ model is studied in detail by using the entanglement measure of negativity. The effects of spin on the thermal entanglement, the threshold temperature, the critical uniform external magnetic field, the nonuniform external magnetic field and the entanglement extremum are discussed, respectively. It is shown that with increasing spin, the entanglement will increase, and then decrease slowly. In addition, we find that entanglement will approach a constant Nc with the increase of DM interaction, the constant increases with the increase of spin, and both the threshold temperature Tc and critical uniform external magnetic field Bc will increase with the increasing spin. Thus high-spin system can inhibit the influence of the external environment better.
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High-Spin States in the Odd-Odd Nucleus 92Nb
WU Yi-Heng, LU Jing-Bin, LUO Peng-Wei, LI Guang-Sheng, LI Hong-Wei, WU Xiao-Guang, HE Chuang-Ye, ZHENG Yun, MA Ke-Yan, YANG Dong, LI Cong-Bo, HU Shi-Peng, LIU Jia-Jian, WANG Jin-Long, YAO Shun-He, CHEN Qi-Ming, ZHONG Jian
Chin. Phys. Lett. 2014, 31 (04):
042102
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DOI: 10.1088/0256-307X/31/4/042102
High spin states of the odd-odd nucleus 92Nb are investigated using the 82Se (14N, 4n)92Nb reaction at a beam energy of 54 MeV. The level scheme of the 92Nb was extended up to Jπ=(16+) at about 7.3 MeV and Jπ=(21?) at about 9.7 MeV. According to systematic analyses and a comparison with the neighboring nucleus, the higher spin states could be interpreted by the multi-particle excitations in the π(f5/2,p3/2,p1/2,g9/2)?ν(p1/2,g9/2,d5/2, g7/2) configuration space.
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The Inversionless Amplification in a Tripod System of 87Rb Atoms in a Magneto-optical Trap
SUN Zhen, JIA Feng-Dong, LV Shuang-Fei, RUAN Ya-Ping, QING Bo, XUE Ping, XU Xiang-Yuan, DAI Xing-Can, ZHONG Zhi-Ping
Chin. Phys. Lett. 2014, 31 (04):
043201
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DOI: 10.1088/0256-307X/31/4/043201
The probe transmission spectra around the atomic transition 52S1/2,F=2→52P3/2,F'=2 of 87Rb are measured in a magneto-optical trap by adding a coupling field around the atomic transition 52S1/2,F=2→52P3/2,F'=2. The inversionless amplification is observed in the spectrum over the atomic transition 52S1/2,F=2→52P3/2,F'=2. The tripod electromagnetically induced transparency is proposed to account for the amplification feature, in which population distributions among these related atomic levels play an important role.
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Simulation and Optimization of Miniature Ring-Endcap Ion Traps
CAO Jian, TONG Xin, CUI Kai-Feng, SHANG Jun-Juan, SHU Hua-Lin, HUANG Xue-Ren
Chin. Phys. Lett. 2014, 31 (04):
043701
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DOI: 10.1088/0256-307X/31/4/043701
With the decrease in dimension of ion traps employed in optical frequency standards and precision spectroscopy, the sensitivity of trapping behavior to trap geometry is more and more prominent. We present a guide for the design and construction of a miniature trap for a single ion confinement, and propose an optimized combination of rring/rendcap≈0.5 and z0≈r0 within the range of r0=0.7±0.2 mm. Compared with the trap used by Huang et al. [ Phys. Rev. A 84 (2011) 053841], the design can lead to an increase in trap pseudo-potential of more than 20% and a reduction on potential anharmonicity of more than 90%. The improvements make the trap closer to an ideal hyperboloidal trap to confine a single ion tightly with the benefit of weaker micro-motion. Considering the imperfection of electrodes machining and traps alignment, we also demonstrate the importance of trap symmetry, especially on two endcap electrodes.
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Distributed Field Rotator Composed of Isolated Components
LIU Guo-Chang, LI Chao, SHAO Jin-Jin, FANG Guang-You
Chin. Phys. Lett. 2014, 31 (04):
044101
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DOI: 10.1088/0256-307X/31/4/044101
Transformation optics offers remarkable control over electromagnetic fields and has recently opened an exciting gateway to design 'field rotator devices'. We propose a distributed field rotator with open windows based on composite transformation optics, which consists of a central circular region and several isolated components. The number, position and size of the components can be controlled freely by the design purpose. Full-wave simulations are performed to demonstrate its function, which is equivalent to a classic field rotator. However, such a distributed rotator makes it much easier to access and make use of the rotated field in the central region, compared to the closed classic field rotator, especially in the case of 3D situations.
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A Compact High Power Laser-Diode Side-Pumped Tm,Ho:YAG Laser Nearly at Room Temperature with Intracavity Tm:YAG Laser
ZHANG Chao, DU Shi-Feng, NIU Yan-Xiong, WANG Cai-Li, WANG Zhi-Chao, XU Jia-Lin, BO Yong, PENG Qin-Jun, CUI Da-Fu, XU Zu-Yan
Chin. Phys. Lett. 2014, 31 (04):
044201
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DOI: 10.1088/0256-307X/31/4/044201
We report a compact high power Tm,Ho:YAG laser nearly at room temperature. The laser-diode side-pumped Tm:YAG and Tm,Ho:YAG laser modules are operated in the same cavity. The laser yields 37.34 W of continuous wave output power under the temperature of 6 °C, corresponding to a maximum slope efficiency of 16.7% when the output power lies from 5.1 W to 27.0 W. This is the first report on the combined Tm:YAG and Tm,Ho:YAG lasers for obtaining high power 2.1 μm laser.
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Design of an Indirect-Drive Pulse Shape for ~1.6 MJ Inertial Confinement Fusion Ignition Capsules
WANG Li-Feng, WU Jun-Feng, YE Wen-Hua, FAN Zheng-Feng, HE Xian-Tu
Chin. Phys. Lett. 2014, 31 (04):
045201
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DOI: 10.1088/0256-307X/31/4/045201
We present a design of indirect-drive pulse shape for inertial confinement fusion ignition capsules using laser energy 1.6 MJ with a moderate gain (~10) on the Shenguang IV laser facility. The trade-off fuel compression (pressure) for resistance to the hydrodynamic instability (HI) in the recent high-foot (HF) implosion campaign [Dittrich T R et al Phys. Rev. Lett. 112 (2014) 055002] is recovered. The proposed design modifies the "main" pulse shape, which features a decompression-recompression step for the fuel shell resulting in higher areal density than that of the "simple" HF design, and thereby approaches the conditions required for ignition avoiding at the expense of more laser energy while holding the HI under control.
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Synergistic Effect of Triple Ion Beams on Radiation Damage in CLAM Steel
YUAN Da-Qing, ZHENG Yong-Nan, ZUO Yi, FAN Ping, ZHOU Dong-Mei, ZHANG Qiao-Li, MA Xiao-Qiang, CUI Bao-Qun, CHEN Li-Hua, JIANG Wei-Sheng, WU Yi-Can, HUANG Qun-Ying, PENG Lei, CAO Xing-Zhong, WANG Bao-Yi, WEI Long, ZHU Sheng-Yun
Chin. Phys. Lett. 2014, 31 (04):
046101
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DOI: 10.1088/0256-307X/31/4/046101
The synergistic effect of triple ion beams is investigated by simultaneous and sequential irradiations of gold, hydrogen and helium ions on the low activation martensitic steel (CLAM) developed in China. The depth profile measurements of the positron annihilation Doppler broadening S parameter are carried out as a function of slow-positron beam energy to examine the produced radiation damage. The synergistic effect of displacement damage and hydrogen and helium on the formation of radiation damage is clearly observed. In the preset case ,this effect suppresses the radiation damage in the CLAM steel due to the helium and/or hydrogen filling of vacancy clusters.
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Ab-Initio Study of Cobalt Impurity Effects on Phonon Spectra, Mechanical and Thermal Properties of Single Wall Carbon Nanotube (5,0)
H. Tashakori, B. Khoshnevisan, F. Kanjouri
Chin. Phys. Lett. 2014, 31 (04):
046301
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DOI: 10.1088/0256-307X/31/4/046301
We use density functional perturbation theory based on the pseudo-potential to calculate the phonon spectrum, phonon density of states, specific heat capacity and mechanical properties of pristine and cobalt doped (5,0) single wall carbon nanotube (CNT). In the calculations, we consider one Co atom in the center of the unit cell of the tube and it is shown that the pristine (5,0) CNT is nonmagnetic while the Co-doped tube becomes magnetic. Young's modulus for both systems is about 1 TPa (after Co-doping it goes slightly higher) and the Poisson ratio for the pristine tube becomes quite a bit larger than the doped one. On the other hand, the calculated value of radial breath mode for the pristine CNT is in good agreement with the experimental reports while after Co-doping it is increased. In addition, heat capacity of the doped CNT is reduced, which leads to some important empirical applications.
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Optical Constants of SiO2 Films Deposited on Si Substrates
JI Yi-Qin, JIANG Yu-Gang, LIU Hua-Song, WANG Li-Shuan, LIU Dan-Dan , JIANG Cheng-Hui, FAN Rong-Wei, CHEN De-Ying
Chin. Phys. Lett. 2014, 31 (04):
046401
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DOI: 10.1088/0256-307X/31/4/046401
SiO2 films were deposited on single-crystalline silicon substrates by ion beam sputtering technology. Optical constants of SiO2 films are calculated from spectroscopic ellipsometry data, transmittance spectra and reflectance spectra by WVASE32 software, and the best fitted method is obtained for calculating optical constants of dielectric materials in the ultraviolet-visible-infrared (UV-VIS-IR) range. In the UV-VIS-NIR spectral range, refractive indices of SiO2 films are calculated separately by both ellipsometry data and reflectance spectra, and the obtained results are almost the same. Complex dielectric functions of SiO2films in the IR spectral range are accurately calculated with infrared transmission spectra using the GenOsc model. The obtained accuracy complex refractive index of SiO2 films in the wavelength region from 0.19 μm to 25 μm is of great importance for the design of high quality coatings, such as ultra-low loss coating.
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High-Efficiency Phosphorescent White Organic Light-Emitting Diodes with Stable Emission Spectrum Based on RGB Separately Monochromatic Emission Layers
ZHANG Zhi-Qiang, LIU Yi-Peng, DAI Yan-Feng, CHEN Jiang-Shan, MA Dong-Ge, ZHANG Hong-Mei
Chin. Phys. Lett. 2014, 31 (04):
046801
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DOI: 10.1088/0256-307X/31/4/046801
Highly efficient phosphorescent white organic light-emitting diodes (WOLEDs) with stable emission spectra are successfully fabricated by using an RGB three-color separately monochromatic emission layer (EML) structure. The EML consists of a sequence of bis(2-methyldibenzo[f, h]quinoxaline) (acetylacetonate) iridium (III) (Ir(MDQ)(acac)) doped tris(4-carbazoyl-9-ylphenyl)amine (TCTA) as the red emission layer, iridium, tris(2-phenylpyidine)(Ir(ppy)) doped TCTA as the green emission layer and iridium(III) [bis(4, 6-difuorophenyl)-pyridinato-N, C2']picolinate (FIrpic) doped a mixed-host of TCTA and tris(4-carbazoyl-9-ylphenyl)amine (26DCz PPy) as the blue emission layer. Without using any out-coupling techniques, the resulting WOLEDs achieve a power efficiency of 42 lm/W at 100 cd/m2, and 34 lm/W at 1000 cd/m2. The WOLEDs also show excellent spectrum stability with bias voltages, remaining the Commission Internationale de L'Eclairage coordinates at (0.44, 0.43) from 1000 cd/m2 to 10000 cd/m2 and the color rendering index is as high as over 80. We contribute the stable emission spectrum to the RGB separate EML structure that successfully suppresses the undesired competition between host-guest energy transfer and direct exciton formation on emissive dopants by effectively controlling the position of exciton recombination region.
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Growth and Morphology of Magnetron-Sputtered TiAl Alloy Thin Films Studied by Atomic Force Microscopy
SHUI Lu-Yu, YAN Biao
Chin. Phys. Lett. 2014, 31 (04):
046802
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DOI: 10.1088/0256-307X/31/4/046802
At the aim of investigating the growth mechanism and morphology evolution of magnetron-sputtered TiAl alloy thin films, we observe the films deposited for different times and find out the variation by atomic force microscopy. Nucleation mechanism and growth kinetics are studied by dynamic scaling, obtained from the morphology evolution of as-deposited TiAl thin films with different growth times. As a result, we demonstrate that the process of film growth goes through three stages, divided by three different growth exponents. The three growth exponents are β1=0.52±0.01, β2=0.71±0.01, and β3=0.17±0.02, respectively. With the deposition time varying from 2 min to 10 min, the roughness exponent α fluctuates in the range 0.61–1.16.
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Optoelectronic Properties, Elastic Moduli and Thermoelectricity of SrAlGa: An Ab Initio Study
Roshan Ali, G. Murtaza, Y. Takagiwa, R. Khenata, Haleem Uddin, H. Ullah, S. A. Khan
Chin. Phys. Lett. 2014, 31 (04):
047102
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DOI: 10.1088/0256-307X/31/4/047102
Half-Heusler compounds are an impressive class of materials with a huge potential for different applications such as in future energy, especially in the fields of thermoelectrics and solar cells. We present ab initio total energy calculations within the modified Becke–Johnson generalized gradient approximation (mBJ-GGA) to obtain the physical properties of SrAlGa compounds. The structural, elastic, acoustic, electronic, chemical bonding, optical, and thermoelectric properties are calculated and compared with the available calculation data. The SrAlGa is found to be a small-band-gap (0.125–0.175 eV) material, suitable for thermoelectric applications with a relatively high Seebeck coefficient. Also, SrAlGa has the potential in the optoelectronic applications due to high optical conductivity and reflectivity in the infrared and visible region of electromagnetic spectra.
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Effects of the Antiferromagnetic Spin Coupling and Interdot Coulomb Repulsion on Kondo Effects in Serial Double Quantum Dots
LI Zeng-Peng, WU Shao-Quan, ZHAO Guo-Ping
Chin. Phys. Lett. 2014, 31 (04):
047201
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DOI: 10.1088/0256-307X/31/4/047201
We theoretically study the effects of the antiferromagnetic (AF) spin coupling and the interdot Coulomb repulsion on the Kondo effects in serial double quantum dots by means of the slave-boson mean-field approximation. Our results indicate that in the weak coupling regime, the AF spin coupling strengthens the Kondo resonance, while the interdot Coulomb repulsion suppresses them for the equilibrium case. In the non-equilibrium case, the AF spin coupling strengthens the Kondo resonance only when J>2.5TK0, while the interdot Coulomb repulsion does not suppress Kondo peaks. In the strong coupling regime, the bias voltage has no effects on the Kondo resonance in this system, and the AF spin coupling increases the height of Kondo peaks only when J<2.5TK0. However, the inter-dot Coulomb repulsion suppresses the spin Kondo effect, which induces the orbit Kondo effect. Moreover, the relevant underlying physics of these problems are discussed.
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Effect of the Minimal Length on the Thermodynamics of Ultra-Relativistic Ideal Fermi Gas
ZHANG Xiu-Ming, SUN Jiu-Xun, YANG Li
Chin. Phys. Lett. 2014, 31 (04):
047301
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DOI: 10.1088/0256-307X/31/4/047301
Based on the generalized uncertainty principle, the thermodynamics of Fermi gas in high density, high pressure and high temperature are calculated. As the temperature and density increases, the energy and entropy becomes saturated and the pressure blows up without any bound. Using the conservation equation of the Robertson–Walker cosmology, we find that, when the energy exceeds the EH=β0?1/2c2Mp, the expansion cannot be driven by the photon gas and the fermion gas. This requires some new physical mechanism related to quantum gravity, such as tachyons and dilatons.
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Electromagnetic and Microwave Absorption Properties of Fe Coating on SiC with Metal Organic Chemical Vapor Reaction
LIU Yuan, LIU Xiang-Xuan, WANG Xuan-Jun, WEN Wu
Chin. Phys. Lett. 2014, 31 (04):
047702
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DOI: 10.1088/0256-307X/31/4/047702
SiC?Fe composites are prepared by metal organic chemical vapor deposition (MOCVD) using silicon carbide (SiC) and iron pentacarbonyl (Fe(CO)5) as the precursors. The structure and morphology analyses demonstrate that the Fe nanoparticles have been deposited on the surface of the SiC particles. In terms of reflection loss (RL), the absorbing frequency band (AFB, the value of RL <?10 dB), and the matching thickness (tm), SiC-Fe composites show the best performances: minimum RL of -31.6 dB with tm=2.0 mm at 15.1 GHz, AFB of 12.9–17.3 GHz, indicating that Fe-doped SiC by MOCVD can significantly improve the electromagnetic properties of SiC and that SiC-Fe composites could be used as an effective microwave absorption material.
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Temperature-Dependent Photoluminescence of Silicon Nanoporous Pillar Array
LI Yong, WANG Xiao-Bo, FAN Zhi-Qiang, LI Xin-Jian
Chin. Phys. Lett. 2014, 31 (04):
047801
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DOI: 10.1088/0256-307X/31/4/047801
Silicon nanoporous pillar array (Si-NPA) is a micron-nanometer hierarchical structure which might be used as functional substrates for constructing optoelectronic nanodevices. This makes understanding the photoluminescence (PL) from Si-NPA important. We measure the PL of Si-NPA in the range of 11–300 K. By analyzing the evolution of the peak energy and intensity with temperature, the ultraviolet, blue, orange and red PL bands from Si-NPA are attributed to the radiative recombination through the deep-levels in silicon oxide, oxygen-related defect states in silicon nanocrystallites (nc-Si), band-to-band transition within nc-Si, and surface/interface states of nc-Si or between nc-Si and SiOx, respectively. At least two non-radiative recombination processes, which are activated at different temperature ranges, are proposed for the PL intensity variation with temperature. These results might provide strong foundations for designing and constructing optoelectronic devices based on silicon nanostructures.
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Improvement of the Injection and Transport Characteristics of Electrons in Organic Light-Emitting Diodes by Utilizing a NaCl N-Doped Layer
XIAO Zhi-Hui, WU Xiao-Ming, HUA Yu-Lin, WANG Li, BI Wen-Tao, BAI Juan-Juan, MU Xue, YIN Shou-Gen
Chin. Phys. Lett. 2014, 31 (04):
047803
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DOI: 10.1088/0256-307X/31/4/047803
The injection and transport characteristics of electrons are enhanced by using sodium chloride (NaCl) as an n-type dopant doped into a 4,7-diphnenyl-1, 10-phe-nanthroline (Bphen) electron-transporting layer, which improves the performance of organic light-emitting diodes (OLEDs). Meanwhile, a NaCl-doped Bphen layer can effectively influence electrical characteristics of the devices, and significantly improve the current and power efficiency. The turn-on voltage and the operation voltage of the optimal device are decreased drastically from 6.5 V and 10.8 V to 3.3 V and 5 V, respectively, compared with those of the reference device. The maximum current efficiency and power efficiency of the optimal device are 7.0 cd/A and 4.4 lm/W at the current density of 16.70 mA/cm2, which are about 1.7 and 4 times higher than those of the reference device, respectively. Moreover, the enhancement of the injection and transport ability for electrons is attributed not only to the reduced energy barrier between Al cathode and Bphen, but also to the increased mobility of electrons by the doping effect of NaCl. Therefore, both the electron injection and transport ability are enhanced, which improve the carrier balance in OLEDs and lead to the better device efficiency.
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Locking Function of a Key Residue in Kinesin's Gating Mechanism
GENG Yi-Zhao, ZHANG Hui, JI Qing, YAN Shi-Wei
Chin. Phys. Lett. 2014, 31 (04):
048702
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DOI: 10.1088/0256-307X/31/4/048702
In kinesin's mechanochemical cycle, ATP's binding to the nucleotide-free leading head is exquisitely gated so that futile hydrolysis is effectively avoided. Experiments show that, when both kinesin heads bind to a microtubule, ATP cannot bind to kinesin's leading head when the neck linker (NL) of this head has a backward orientation. How NL's backward orientation is maintained needs understanding on a structural basis. By using steered molecular dynamics and mutation simulations, we investigate the backward-pointing conformation of the leading head's NL under different inter-head tensions. We find that the NL cannot keep in a strict backward orientation solely by the inter-head tension. LYS325 (amino acid sequence in 2KIN) has an assistant locking function which locks the NL and β0 to the β-domain. This locking function has an enhanced positive cooperation with the inter-head tension. When the inter-head tension is weakened, this locking function can be broken, resulting in a loose backward orientation of the NL. The difference between the strict and loose backward orientation of the NL might be a crucial factor in the gating mechanism. These results are consistent with relevant experiments and proposals.
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Hadronic Scenarios for Gamma-Ray Emission from Three Supernova Remnants Interacting with Molecular Clouds
YU Huan, FANG Jun, ZHANG Li
Chin. Phys. Lett. 2014, 31 (04):
049801
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DOI: 10.1088/0256-307X/31/4/049801
GeV γ-rays detected with the large area telescope on board the Fermi Gamma-ray space telescope in the direction of HB21, MSH 17-39 and G337.0-0.1 have been recently reported. The three supernova remnants (SNRs) show interactions with molecular clouds, and they are effective gamma-ray emitters as the relativistic protons accelerated by the SNR shocks inelastically colliding with the dense gas in the clouds. The origin of the observed γ-rays for the three remnants is investigated in the scenario of the diffusive shock acceleration. In the model, a part of the SNR shock transmits into the nearby molecular clouds, and the shock velocity is greatly reduced. As a result, a shock with a relatively low Alfvén Mach number is generated, and the spectra of the accelerated protons and theγ-ray photons produced via proton-proton interaction can be obtained. The results show that the observed γ-ray spectra for the three SNRs interacting with the molecular clouds can be reproduced. It can be concluded that the hadronic origin of the γ-rays for the three SNRs is approved, and the ability of SNR shocks to accelerate protons is also supported.
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52 articles
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