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The β Decay of 21N
LOU Jian-Ling, LI Zhi-Huan, YE Yan-Lin, JIANG Dong-Xing, HUA Hui, LI Xiang-Qing, ZHANG Shuang-Quan, ZHENG Tao, GE Yu-Chen, KONG Zan, LV Lin-Hui, LI Chen, LU Fei, FAN Feng-Ying, LI Zhong-Yu, CAO Zhong-Xin, MA Li-Ying, Faisal, XU Hu-Shan, HU Zheng-Guo, WANG Meng, LEIXiang-Guo, DUAN Li-Min, XIAO Zhi-Gang, ZHAN Wen-Long, XIAO Guo-Qing, HUANG Tian-Heng, FU Fen, ZHANG Xue-Heng, ZHENG Chuan, YU Yu-Hong, TU Xiao-Lin, ZHANG Ya-Peng, YANG Yan-Yun, ZHANG Hong-Bin, TANG Bin, TIAN Yu-Lin, OU Yang-Zhen, HUANG Mei-Rong, XU Zhi-Guo, YUE Ke, GAO Qi
Chin. Phys. Lett. 2008, 25 (6):
1992-1995
.
The β-delayed neutron and γ energy spectra taken from the decay of neutron-rich nucleus 21N were measured by using the β-γ and β-n coincidence detection method. Thirteen new neutron groups ranging from 0.28MeV to 4.98MeV and with a total branching ratio of 88.7±4.2% were observed and presented. One γ transition with an energy of 1222keV emitted from the excited state of 21O, and four γ transitions with energies of 1674, 2397, 2780, and 3175keV emitted from the excited states of 20O were identified in the β decay chain of 21N. The β decay half-life for 21N is determined to be 82.9±1.9ms. The uncertainty of half-life is much smaller than the previous result.
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High Spin States in Odd--Odd 160Tm Nucleus
SUN Liang, LU Jing-Bin, YANG Dong, WANG Lie-Lin, YANG Sen, LIU Yun-Zuo, ZHAO Yan-Xin, ZHOU Wen-Ping, MA Ying-Jun, ZHU Li-Hua, WU Xiao-Guang, LI Guang-Sheng
Chin. Phys. Lett. 2008, 25 (6):
1996-1999
.
High-spin states of 160Tm are studied by the 146Nd19F, 5n) reaction at a beam energy of 102MeV. The previously known π h11/2⊕υi13/2 yrast band and π h11/2⊕υh9/2 side band are confirmed. The level scheme is enriched and more low-lying levels are observed. A new side band is observed and assigned as the favoured signature partner of π d3/2⊕υi13/2. The spin of this band is assigned with the energy level systematics. It is pointed out that the $B(M1)/B(E2)$ ratios increase rapidly at the high frequency approaching the second crossing in the π11/2⊕υi13/2 band, which is closely related to the alignment gain of the aligned i13/2 quasineutron.
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Density and Symmetric Potential Dependences of Isoscaling Behaviour in the Lattice Gas Model
SU Qian-Min, , MA Yu-Gang, TIAN Wen-Dong, FANG De-Qing, CAI Xiang-Zhou, WANG Kun
Chin. Phys. Lett. 2008, 25 (6):
2000-2003
.
Isoscaling behaviour of the statistical emission fragments from the equilibrated sources with Z=30 and N=30, 33, 36 and 39 is investigated in the framework of the isospin-dependent lattice gas model. The dependences of isoscaling parameters α on source isospin asymmetry, temperature and freeze-out density are studied, and the `symmetry energy' is deduced from isoscaling parameters. The results show that symmetry energy Csym is insensitive to the change of temperature but follows the power-law dependence on the freeze-out density ρ. The effect of strength of asymmetry of nucleon--nucleon interaction potential on the density dependence of the symmetry energy is discussed.
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Dissociation Energies of Diatomic Molecules
FAN Qun-Chao, SUN Wei-Guo
Chin. Phys. Lett. 2008, 25 (6):
2012-2015
.
Molecular dissociation energies of 10 electronic states of alkali molecules of KH,7LiD, 7LiH, 6LiH, NaK, NaLi and NaRb are studied using the highest three accurate vibrational energies of each electronic state, and an improved parameter-free analytical formula which is obtained starting from the LeRoy--Bernstein vibrational energy expression near the dissociation limit. The results show that as long as the highest three vibrational energies are accurate, the current analytical formula will give accurate theoretical dissociation energies Detheory, which are in excellent agreement with the experimental dissociation energies Deexpt.
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Observation of Nano-Dots on HOPG Surface Induced by Highly Charged Arq+ Impact
WANG Tie-Shan, YANG Xiu-Yu, B. E. O'Rourke, XU He, CHEN Liang, CHENG Rui, PENG Hai-Bo, Y. Mitsuda, Y. Yamazaki
Chin. Phys. Lett. 2008, 25 (6):
2020-2022
.
Highly charged ions (HCIs) have huge potential energy due to their high charge state. When a HCI reaches a solid surface, its potential energy is released immediately on the surface to cause a nano-scale defect. Thus, HCIs are expected to be useful for solid-surface modifications on the nano-scale. We investigate the defects on a highly oriented pyrolytic graphite (HOPG) surface induced by slow highly charged Arq+ ions with impact energy of 20--2000qeV with scanning probe microscopy (SPM). In order to clarify the role of kinetic and potential energies in surface modification, the nano-defects are characterized in lateral size and height corresponding to the kinetic energy and charge state of the HCIs. Both the potential energy and kinetic energy of the ions may influence the size of nano-defect. Since potential energy increases dramatically with increasing charge state, the potential energy effect is expected to be much larger than the kinetic energy effect in the case of extremely high charge states. This implies that pure surface modification on the nano-scale could be carried out by slow highly charged ions. The mean size of nano-defect region could also be controlled by selecting the charge state and kinetic energy of HCI.
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Multi-Slit Diffraction of Evanescent Electromagnetic Waves
SONG Zhen-Ming, CHEN Yong-Yao, XU Bo, LI Yan-Feng, HU Ming-Lie, XING Qi-Rong, ZHANG Zhi-Gang, CHAI Lu, WANG Qing-Yue
Chin. Phys. Lett. 2008, 25 (6):
2033-2036
.
The well-known Fraunhofer multi-slit diffraction is described as the multi-slit interference modulated by the single-slit diffraction, namely the multiplication between the single-slit diffraction factor and the multi-slit interference factor. By considering the simplified argument we show that the multi-slit diffraction of evanescent waves which are in the near-field region also has the interference and diffraction effects, and that this two-fold effect can be expressed as the convolution of the diffraction factor and the interference factor. Our conclusion could be helpful to understand the contribution of evanescent waves to the optical responses of sub-wavelength structures such as slits and grooves.
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Absorption Changes Induced by Off-Resonance Driving a Degenerate Two-Level System
CAI Jin, ZHOU Hai-Tao, WANG Wen-Qi, LI Zhong-Hua, LI Tao, ZHANG Jun-Xiang
Chin. Phys. Lett. 2008, 25 (6):
2041-2044
.
The alteration of atomic absorption via quantum coherence is observed in the degenerate two-level atomic system. It is shown that when the detuning of coupling field equals to that of probe light, i.e. two-photon resonance, the reduction of atomic absorption via electromagnetically induced transparency occurs. However, when we tune the coupling field to two-photon off-resonance, the enhancement of absorption is obtained for the probe field. The influences of one-photon detuning and intensity of coupling field on absorption are also experimentally demonstrated.
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Nonlinear Optical Properties of Novel Polymeric Rare Earth Phthalocyanine Studied Using Picosecond Z-Scan Technique
ZHAO Peng, XU Song, LI Zhong-Yu, ZHANG Fu-Shi
Chin. Phys. Lett. 2008, 25 (6):
2058-2061
.
Three novel tri-dimensional phthalocyanine polymers, with lanthanum (LaPPc), gadolinium (GdPPc) and ytterbium (YbPPc) as centric atoms, have been synthesized from a tetranuclear phthalonitrile. Third-order optical nonlinearities of these compounds in DMF solution are measured by a picosecond Z-sacn technique at 532nm. It is found that all the compounds show reverse saturation absorption and nonlinear self-focus refraction effect. The second-order molecular hyperpolarizabilities are calculated to be 1.82×10-29, 1.48×10-29 and 1.45×-29 esu for LaPPc, GdPPc and YbPPc, respectively. The differences among their nonlinear optical properties are attributed to the special tri-dimensional structure and the variation in rare earth atoms.
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Onset of Unsteady Horizontal Convection in Rectangular Tank at Pr=1
SUN Liang, MA Dong-Jun, ZHANG Wei, SUN De-Jun
Chin. Phys. Lett. 2008, 25 (6):
2121-2124
.
The horizontal convection within a rectangular tank is numerically simulated. The flow is found to be unsteady at high Rayleigh numbers. There is a Hopf bifurcation of Ra from steady solutions to periodic solutions, and the critical Rayleigh number Rac is obtained to be Rac=5.5377×108 for the middle plume forcing at Pr=1, which is much larger than the value previously obtained. In addition, the unstable perturbations are always generated from the central jet, which implies that the onset of instability is due to velocity shear (shear instability) other than thermally dynamics (thermal instability). Finally, Paparella and Young's first hypotheses [J. Fluid Mech. 466(2002)205] about the destabilization of the flow is numerically proven, i.e. the middle plume forcing can lead to a destabilization of the flow.
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Large Relative Raman Shift for Molecules Adsorbed on Metallic Nano-particles
LI Xiao-Yun, XIA Yu-Xing, ZHAN Li, LENG Jiang-Hua
Chin. Phys. Lett. 2008, 25 (6):
2140-2143
.
The enhancement of two order-of-magnitudes is observed in surface-enhanced Raman spectroscopy (SERS) of gases (CO, C2H2, C2H4, etc) adsorbed on nitric acid-roughened metal foil. In addition, some Raman lines of gases adsorbed on these active substrates show larger frequency shifts and linewidth broadening, compared with the Raman spectroscopy of free gases. Using the two-oscillator electromagnetic model, we explain this phenomenon. It is related to the large non-regular particles on the active substrate we prepared. It is found that the parameters of the surface-plasmon dispersion, the distance of molecules from the surface and the radius of particles play crucial roles on the relative large Raman shifts.
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Effects of Annealing on Microstructure and Optical Properties of TiO2 Sculptured Thin Films
XIAO Xiu-Di, DONG Guo-Ping, QI Hong-Ji, FAN Zheng-Xiu, HE Hong-Bo, SHAO Jian-Da
Chin. Phys. Lett. 2008, 25 (6):
2181-2184
.
The evolution of microstructure and optical properties of TiO2 sculptured thin films under thermal annealing is reported. XRD, field emission SEM, UV-Vis-NIR spectra are employed to characterize the microstructural and optical properties. It is found that the optimum annealing temperature for linear birefringence is 500°C. The maximum of transmission difference for linear birefringence is up to 18%, which is more than twice of that in as-deposited thin films. In addition, the sample annealed at 500°C has a minimum of column angle about 12°C. The competitive process between the microstructural and optical properties is discussed in detail. Post-annealing is a useful method to improve the linear birefringence in sculptured thin films for practical applications.
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Demonstration of GaN/InGaN Light Emitting Diodes on (100) β-Ga2O3 Substrates by Metalorganic Chemical Vapour Deposition
XIE Zi-Li, ZHANG Rong, XIA Chang-Tai, XIU Xiang-Qian, HAN Ping, LIU Bin, ZHAO Hong, JIANG Ruo-Lian, SHI Yi, ZHENG You-Dou
Chin. Phys. Lett. 2008, 25 (6):
2185-2186
.
The growth and fabrication of GaN/InGaN multiple quantum well (MQW) light emitting diodes (LEDs) on (100) β-Ga2O3 single crystal substrates by metal-organic chemical vapour deposition (MOCVD) technique are reported. x-ray diffraction (XRD) θ-2θ scan spectroscopy is carried out on the GaN buffer layer grown on a (100) β-Ga2O3 substrate. The spectrum presents several sharp peaks corresponding to the (100) β-Ga2O3 and (004) GaN. High-quality (0002) GaN material is obtained. The emission characteristics of the GaN/InGaN MQW LED are measurement. The first green LED on β-Ga2O3 with vertical current injection is demonstrated.
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Thermoelectric Performance of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)
JIANG Feng-Xing, XU Jing-Kun, LU Bao-Yang, XIE Yu, HUANG Rong-Jin, LI Lai-Feng
Chin. Phys. Lett. 2008, 25 (6):
2202-2205
.
Thermoelectric (TE) performances are systematically investigated for the pellets of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with different organic additives and heating process as organic TE materials. The electrical conductivity, Seebeck coefficient and thermal conductivity versus temperature are determined, respectively. It is found that there is no distinct change for the Seebeck coefficient among each sample with the additions of dimethyl sulfoxide and ethylene glycol. The thermal conductivity measured in a wide range of temperature indicates that the PEDOT:PSS pellet have an extremely low value. The highest figure of merit (ZT= 1.75×10-3) is observed at 270K among the PEDOT:PSS pellets.
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Superconductivity at 55K in Iron-Based F-Doped Layered Quaternary Compound Sm[O1-xFx]FeAs
REN Zhi-An, LU Wei, YANG Jie, YI Wei, SHEN Xiao-Li, LI Zheng-Cai, CHE Guang-Can, DONG Xiao-Li, SUN Li-Ling, ZHOU Fang, ZHAO Zhong-Xian
Chin. Phys. Lett. 2008, 25 (6):
2215-2216
.
We report the superconductivity in iron-based oxyarsenide Sm[O1-xFx]FeAs, with the onset resistivity transition temperature at 55.0K and Meissner transition at 54.6K. This compound has the same crystal structure as LaOFeAs with shrunk crystal lattices, and becomes the superconductor with the highest critical temperature among all materials besides copper oxides up to now.
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Angle Integrated Photoemission Study of SmO0.85F0.15FeAs
OU Hong-Wei, ZHAO Jia-Feng, ZHANG Yan, SHEN Da-Wei, ZHOU Bo, YANGLe-Xian, HE Cheng, CHEN Fei, XU Min, WU Tao, CHEN Xian-Hui, CHEN Yan, FENG Dong-Lai
Chin. Phys. Lett. 2008, 25 (6):
2225-2227
.
The electronic structure of the new superconductor SmO1-xFxFeAs (x=0.15) is studied by angle-integrated photoemission spectroscopy. Our data show a sharp feature very close to the Fermi energy, and a relative flat distribution of the density of states between 0.5eV and 3eV binding energy, which agrees well with the band structure calculations considering an antiferromagnetic ground state. No noticeable gap opening is observed at 12K below the superconducting transition temperature, indicating the existence of large ungapped regions in the Brillouin zone.
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Field Dependence of π-Band Superconducting Gap in MgB2 Thin Films from Point-Contact Spectroscopy
HUANG Yan, WANG Yong-Lei, SHAN Lei, JIA Ying, YANG Huan, WEN Hai-Hu, ZHUANG Cheng-Gang, LI Qi, CUI Yi, XI Xiao-Xing,
Chin. Phys. Lett. 2008, 25 (6):
2228-2231
.
We present the results of point-contact spectroscopy measurements on High-quality epitaxial MgB2 thin films with injected current along the c-axis. The temperature and field dependences of π-band properties with the field parallel to (H⊥) or perpendicular to (H|| the c-axis are investigated in detail. When a magnetic field is applied, either parallel or perpendicular to the c-axis, the density of the quasiparticle state (DOS) of the π-band proliferates quickly with increasing field, while the gap amplitude of the π-band decreases slowly, which is different from the recent theoretical calculations, showing a field dependent competition between the interband scattering and the pair-breaking effects.
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The Minimum Model for the Iron-Based Superconductors
LI Jian, WANG Yu-Peng
Chin. Phys. Lett. 2008, 25 (6):
2232-2234
.
A single band t-U-J1-J2 model is proposed as the minimum model to describe the superconductivity of the newly discovered iron-based superconductors R(O1-xFx)FeAs and RO1-xFeAs (R=La, Ce, Sm, Pr, Nd, Gd). With the mean-field approach, it is found that the pairing occurs in the d-wave channel. In the likely parameter region of the real materials, by lowering temperature, the system enters firstly the dxy superconducting phase with D4h-symmetry and then enters the time-reversal-symmetry-broken dxy+idx2-y2 superconducting phase with C4h-symmetry.
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Element Substitution Effect in Transition Metal Oxypnictide Re(O1-xFx)TAs (Re=rare earth, T=transition metal)
CHEN Gen-Fu, LI Zheng, WU Dan, DONG Jing, LI Gang, HU Wan-Zheng, ZHENGPing, LUO Jian-Lin, WANG Nan-Lin
Chin. Phys. Lett. 2008, 25 (6):
2235-2238
.
Different element substitution effects in transition metal oxypnictide Re(O1-xFx)TAs, with Re=La, Ce, Nd, Eu, Gd, Tm, T=Fe, Ni, Ru, are studied. Similar to the La- or Ce-based systems, we find that the pure NdOFeAs shows a strong resistivity anomaly near 145K, which is ascribed to the spin-density-wave instability. Electron doping by F increases Tc to about 50K. While in the case of Gd, Tc is reduced below 10K. The tetragonal ZrCuSiAs-type structure could not be formed for Eu or Tm substitution in our preparing process. For the Ni-based case, although both pure and F-doped LaONiAs are superconducting, no superconductivity is found when La is replaced by Ce in both the cases, instead a ferromagnetic ordering transition is likely to form at low temperature in the undoped sample. We also synthesize LaO1-xFxRuAs and CeO1-xFxRuAs compounds. The metallic behaviour is observed down to 4K.
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Influence of Zn Ions Codoping on Luminescence Properties of PbWO4:RE(RE=La, Yb, Y)
XU Yan-Ling, WANG Rui, WANG Bin-Ju, LIU Wei-Hai, WANG Jia, WANG Miao, YANG Tong-Yong
Chin. Phys. Lett. 2008, 25 (6):
2246-2248
.
Zn and RE (RE=La, Yb, Y) ions co-doped PbWO4 (PWO) single crystal grown by the Czochralski technique are characterized by x-ray diffraction (XRD), optical transmission spectra, and photoluminescence (PL). The doping of Zn ions shows distinct effects on the properties of PWO:RE crystals. At low concentration of Zn ions (200ppm), the luminescence intensity is quite weak for (Zn,La)-doped PWO, but is substantially strong for (Zn,Yb)-doped PWO. The blue luminescence intensity is significantly enhanced with the increasing Zn ions doping for PWO:Y. The trivalent ions codoping can increase the ratio of the blue luminescence contributing to the fast components of light yield. Yb ions can enhance efficiency of luminescence in PWO:Yb:Zn because they may act as a luminous sensitization agent which can be involved in the efficient energy transfer and storage of the radiative process.
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Red and Near-Infrared Electroluminescences from Metal-Free Phthalocyanine
FAN Zhao-Qi, CHENG Chuan-Hui, YE Kai-Qi, YU Shu-Kun, HE Wei, XIA Dao-Cheng, GUO Zhen-Qiang, SHENG Ren-Sheng, WANG Xu, DU Xi Guang, DU Guo-Tong,
Chin. Phys. Lett. 2008, 25 (6):
2261-2264
.
Organic light emitting diodes are fabricated based on metal-free phthalocyanine (H2Pc) doped into tris-(8-hydroxyquinoline) aluminium (Alq3). The device structure is ITO/NPB (30nm)/Alq3: H2Pc(30nm)/BCP(20nm) /Alq3(20 nm)/Al. In the light-emitting layers, H2Pc concentrations are varied from 0wt% to 100wt%. The emissions around 708nm and 800nm appear at low concentrations, while the emissions around 910nm and 930nm appear at high concentrations. The emissions around 708nm and 800nm are from H2Pc monomers. The emissions around 910nm and 930nm are from H2Pc aggregates. The dominant mechanism in the doped devices is direct charge trapping.
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Three-Step Growth Optimization of AlN Epilayers by MOCVD
PENG Ming-Zeng, GUO Li-Wei, ZHANG Jie, YU Nai-Sen, ZHU Xue-Liang, YANJian-Feng, GE Bin-Hui, JIA Hai-Qiang, CHEN Hong, ZHOU Jun-Ming
Chin. Phys. Lett. 2008, 25 (6):
2265-2268
.
A three-step growth process is developed for depositing high-quality aluminium-nitride (AlN) epilayers on (001) sapphire by low pressure metalorganic chemical vapour deposition (LP-MOCVD). We adopt a low temperature (LT) AlN nucleation layer (NL), and two high temperature (HT) AlN layers with different V/III ratios. Our results reveal that the optimal NL temperature is 840--880°C, and there exists a proper growth switching from low to high V/III ratio for further reducing threading dislocations (TDs). The screw-type TD density of the optimized AlN film is just 7.86×106cm-2, about three orders lower than its edge-type one of 2×109cm-2 estimated by high-resolution x-ray diffraction (HRXRD) and cross-sectional transmission electron microscopy (TEM).
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Cs+-K+ Exchange in Z-Cut KTiOPO4 Crystal Covered with Chromium Masking Layer
ZHANG Rui-Feng, LU Fei, LIAN Jie, LIU Han-Ping, LIU Xiang-Zhi, WANG Liang-Ling, WANG Ke-Ming, LU Qing-Ming
Chin. Phys. Lett. 2008, 25 (6):
2281-2284
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Cs+--K+ ion exchanges are performed on z-cut KTiOPO4 crystals with chromium coating covered. The temperature of ion exchange is 430°C, and the time range from 15min to 30min. The dark mode spectra of the samples are measured by the prism coupling method. The channel structures on the samples are observed by a microscope and the near field pattern of the channel waveguides are measured by the end-fire coupling method. The refractive index of the samples increases and the increments at surface are modulated due to the existence of Cr film. In the region covered by Cr film, the refractive index of the samples at the surface increases dramatically in a shallow layer. The results of energy dispersive x-ray spectra indicate that in the region covered with Cr film, Cr ions participate in the ion exchange process, and enhance the refractive index. The results may provide a possibility that achieves index enhancement and Cr doping synchronically.
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Message Spreading and Forget--Remember Mechanism on a Scale-Free Network
LI Wei, GU Jiao, CAI Xu
Chin. Phys. Lett. 2008, 25 (6):
2303-2306
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We study message spreading on a scale-free network, by introducing a novel forget-remember mechanism. Message, a general term which can refer to email, news, rumor or disease, etc, can be forgotten and remembered by its holder. The way the message is forgotten and remembered is governed by the forget and remember function, F and R, respectively. Both F and R are functions of history time t concerning individual's previous states, namely being active (with message) or inactive (without message). Our systematic simulations show at the low transmission rate whether or not the spreading can be efficient is primarily determined by the corresponding parameters for F and R.
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Role of Clustering Coefficient on Cooperation Dynamics in Homogeneous Networks
WU Gang, GAO Kun, YANG Han-Xin, WANG Bing-Hong
Chin. Phys. Lett. 2008, 25 (6):
2307-2310
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Based on previous works, we give further investigations on the Prisoners' Dilemma Game (PDG) on two different types of homogeneous networks, i.e.~the homogeneous small-world network (HSWN) and the regular ring graph. We find that the so-called resonance-like character can occur on both the networks. Different from the viewpoint in previous publications, we think the small-world effect may be unnecessary to produce this character. Therefore, over these two types of networks, we suggest a common understanding in the viewpoint of clustering coefficient. Detailed simulation results can sustain our viewpoint quite well. Furthermore, we investigate the Snowdrift Game (SG) on the same networks. The difference between the outputs of the PDG and the SG can also sustain our viewpoint.
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Note on Two-Phase Phenomena in Financial Markets
JIANG Shi-Mei, CAI Shi-Min, ZHOU Tao, , ZHOU Pei-Ling
Chin. Phys. Lett. 2008, 25 (6):
2319-2322
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The two-phase behaviour in financial markets actually means the bifurcation phenomenon, which represents the change of the conditional probability from an unimodal to a bimodal distribution. We investigate the bifurcation phenomenon in Hang--Seng index. It is observed that the bifurcation phenomenon in financial index is not universal, but specific under certain conditions. For Hang--Seng index and randomly generated time series, the phenomenon just emerges when the power-law exponent of absolute increment distribution is between 1 and 2 with appropriate period. Simulations on a randomly generated time series suggest the bifurcation phenomenon itself is subject to the statistics of absolute increment, thus it may not be able to reflect essential financial behaviours. However, even under the same distribution of absolute increment, the range where bifurcation phenomenon occurs is far different from real market to artificial data, which may reflect certain market information.
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Annual Variation and Global Structures of The DE3 Tide
CHEN Ze-Yu, LU Da-Ren
Chin. Phys. Lett. 2008, 25 (6):
2323-2326
.
The SABER/TIMED temperatures taken in 2002--2006 are used to delineate the tidal signals in the middle and upper atmosphere. Then the Hough mode decomposition is applied with the DE3 tide, and the overall features of the seasonal variations and the complete global structures of the tide are observed. Investigation results show that the tide is most prominent at 110km with the maximal amplitude of >9K, and exhibits significant seasonal variation with its maximum amplitude always occurring in July every year. Results from the Hough mode decomposition reveal that the tide is composed primarily of two leading propagating Hough modes, i.e., the (-3, 3) and the (-3, 4) modes, thus is equatorially trapped. Estimation of the mean amplitude of the Hough modes show that the (-3, 3) mode and (-3, 4) mode exhibit maxima at 110km and 90km, respectively. The (-3, 3) mode plays a predominant role in shaping the global latitude--height structure of the tide, e.g., the vertical scale of>50km at the equator, and the annual course. Significant influence of the (-3, 4) mode is found below 90km, where the tide exhibits anti-symmetric structure about the equator; meanwhile the tide at northern tropical latitudes exhibits smaller vertical wavelength of about 30km
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110 articles
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