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191.
从π介子核子散射振幅出发,根据Mandelstam表示和么正条件,对于奇异量子数为零、重子数为1的费米子Regge轨迹,求得了下列结果:(1)位置参数α(s)的解析性,只有右方物理割而无左方动力割,但是左方有从s=0到-∞的运动学割。(2)当s<0时α(s)取复数值,并且还有一条同它成复共轭(在s<0范围内)的Regge轨迹。这一对轨迹它们的J-宇称相同,但是空间宇称相反。02时,α(s)为实数。不同宇称的轨迹对s的依赖不同。(3)讨论了费米子Regge迹在阈能(W0=M+μ)附近的行为。凡是与共振态、束缚态有关的Regge轨迹,α(W0)≠0。求得了在阈附近的表示,定性方面同玻色子轨迹相同。(4)还有一大类Regge轨迹,它们同共振态、束缚态无关,α(W0)=0。这类轨迹在能量趋近阈能时,有无穷多个极点趋于ReJ=0(即我们在费米子情况下得到Gribov-Pomeranchuk极点凝聚现象),这类轨迹当能量由阈下趋于阈时,从J平面左半平面共轭成对趋于ReJ=0;当能量从阈上趋于阈时,成对地从第一和第三象限趋于ReJ=0。所有这些极点实数部分Reα→0比虚数部分Imα→0快一或二个数量级。J平面原点是一个凝聚点,这类“非动力”的Regge轨迹阈行为,无论对玻色子、费米子,以至非相对论势散射,定性都相似(只是凝聚的轴线和点不同)。它们实际上是s矩阵在阈的普遍性质的反映。 相似文献
192.
193.
ZHAO JianWen QIAN Jun SHEN YongQiang WANG XiaoHua SHI AiHua & LEE ChunWei College of Chemistry Chemical Engineering Jishou University Jishou China Printable Electronics Research Centre Suzhou Institute of Nanotech Nano-bionics Chinese Academy of Sciences Suzhou China Key Laboratory of Photochemical Conversion Optoelectronic Materials TIPC Beijing China School of Materials Science Engineering Nanyang Technological University Si... 《中国科学B辑(英文版)》2011,(9)
Here we report a simple and scalable method to fabricate high performance thin-film field-effect transistors(FETs) with high yield based on chemically functionalized single-walled carbon nanotubes(SWNTs) by organic radical initiators.The UV-Vis-NIR spectra,Raman spectra and electrical characterization demonstrated that metallic species in CoMoCat 65 and HiPco SWNTs could be effectively eliminated after reaction with some organic radical initiators.The effects of the substrate properties on the electrical pr... 相似文献
194.
TIMO A LÄHDE EVGENY EPELBAUM HERMANN KREBS DEAN LEE ULF-G MEISSNER GAUTAM RUPAK 《Pramana》2014,83(5):651-659
We review the calculation of the Hoyle state of 12C in nuclear lattice effective field theory (NLEFT) and its anthropic implications in the nucleosynthesis of 12C and 16O in red giant stars. We also analyse the extension of NLEFT to the regime of medium-mass nuclei, with emphasis on the determination of the ground-state energies of the α nuclei 16O, 20Ne, 24Mg, and 28Si by Euclidean time projection. Finally, we discuss recent NLEFT results for the spectrum, electromagnetic properties, and α-cluster structure of 16O. 相似文献
195.
Interatomic potential energy curves are presented for the Na+—Rg (Rg = He, Ne and Ar) cationic complexes. The curves are calculated at the CCSD(T)/aug-cc-pVQZ level of theory, with correction for basis set superposition error being performed point-by-point. Ninety-six different bond lengths are used in the generation of the curves. From the curves rovibrational energy levels are calculated. These, in turn, are used to calculate the heat of formation of the cationic complexes, both by calculating partition functions under the assumption of a rigid rotor, harmonic oscillator, and also explicitly using the calculated rovibrational energy levels. The long range region of each of the curves is used to derive the D 4 and D 6 parameters, the former being used to derive the static polarizability a 1 of each of the Rg atoms and the latter the first dispersion coefficients, C 6(Na+—Rg). 相似文献
196.
Starting with H+[CH3C(O)CH2C(O)CH3] (denoted H+PD), the protonated diketone-water clusters H+PD(H2O) n (n = 1–3) have been characterized by density functional theory calculations in combination with vibrational predissociation spectroscopy to explore the conformational changes of a protonated bifunctional ion solvated by water in the gas phase. Theoretical calculations for H+PD revealed that the ion contains an intramolecular hydrogen bond (IHB), with two oxygen atoms bridged by the extra proton in an O—H+ … O form. Attachment of one water molecule to it readily ruptures this IHB, replacing the H+ by the H3O+ moiety. Further replacement of the IHB by two water molecules occurs at n = 2 and the ?C(O)CH2C(O)- chain is fully opened (or unfolded) after transfer of the extra proton to the water trimer at n = 3. To verify the computational findings, infrared spectroscopic measurements were performed using a vibrational predissociation ion trap spectrometer to identify cluster isomers from the signatures of hydrogen bonded and non-hydrogen bonded OH stretching spectra of H+PD(H2O)2,3 produced in a corona discharge supersonic expansion. Besides open form isomers, evidence for the formation of water-bridged structures has been found for H+PD(H2O)3 at an estimated temperature of 200 K. A detailed illustration of the unfolding steps as well as the energy profiles for the evolution of a two-water bridge isomer from the protonated H+PD monomer are analysed pictorially (including both stable intermediates and transition states) in the present investigation. 相似文献
197.
Grand canonical Monte Carlo (GCMC) simulations have been performed to investigate the components of the force between parallel charged surfaces in an electrolyte. The solvent primitive model (SPM) was used to investigate the effect of neutral hard sphere solvent particles on the force between the surfaces. The effects of particle size, wall charge density, charge valency of the electrolyte, and the exclusion of neutral hard sphere are discussed. When solvent particles are considered, the total force between the charged surfaces is always repulsive, even for divalent counterions. This is different from the earlier conclusion reached with a restricted primitive model electrolyte. The repulsive force decreases in going from monovalent counterions to divalent counterions. 相似文献
198.
C. CHAUDHURI Y.-S. WANG J. C. JIANG Y. T. LEE H.-C. CHANG G. NIEDNER-SCHATTEBURG 《Molecular physics》2013,111(14):1161-1173
Size-selected hydroxide ion water tetramers and pentamers [OH-(H2O)4,5], produced by a supersonic expansion, have been investigated using vibrational predissociation spectroscopy in conjunction with ab initio calculations based on density functional theory (DFT). The observed spectra in the frequency range 2650–3850 cm?1 show some broad absorption bands attributed to the free and hydrogen bonded OH stretches of OH-(H2O)4,5 at an estimated cluster temperature of 170 K. DFT calculations performed at the B3LYP/6-31 + G* level reveal five and eight possible low lying isomeric forms for OH-(H2O)4 and OH-(H2O)5, respectively. The global minimum isomer of the tetramer is tri-solvated cyclic, which is energetically more stable than the tetra-solvated wheel-shaped form with an OH- ion at its centre. Compact cage-like lowest energy structures are found for the pentamer, in which the water molecules can act either as a single-donor-single-acceptor, as a double-proton-donor, or as a double-donor-single-acceptor in both the firs1183t a1192nd the second solvation shell of the OH- ion core. Interconversion among the isomers appears to be rapid as manifested in the observed spectra dominated by broad and congested absorptions. To understand the nature of spectral broadening and congestion, systemic comparisons of the results are made against those of the corresponding protonated cations, H+(H2O)n|1 and the corresponding halide anions, X-(H2O)n X = F, Cl, Br, and I. It is suggested that the spectral complexities observed for OH-(H2O)4,5 are predominantly a result of sampling configurations with a large distribution of Osolvent-Oion-Osolvent angles and Osolvent … H-Osolvent distances between water molecules in the firs1175t a1181nd/or second hydration shells, together with the existence of more than one isomer in the supersonic expanson and rapid isomeric interconversion among them. 相似文献
199.
吡啶修饰的线性五核金属化合物[Ni5(μ-dmpzda)4(NCS)2][ dmpzda-H2=N,N’-Di(4-methyl pyrydin-2-yl)pyrazine-2,6-diamine]被合成并表征,其电化学和磁性被报告。 化合物含有接近180º的 Ni-Ni-Ni角,末端含有两个轴配体的Ni5 线性链。这个五核线性金属链被四个顺式的dmpzda2-配体螺旋包裹。化合物中存在两种类型的Ni-Ni键长:末端连接有轴配体的Ni-Ni键长被配体影响,其键长为2.3821 Å;内部的Ni-Ni距离比较短,为2.2959 Å。两末端的Ni(II)离子由于连接轴配体构成四方锥形(NiN4NCS)并存在较长的Ni-N 键长(2.103 Å),这个键长符合高自旋Ni(II)构型。内部的三个Ni-N 距离为1.886-1.906 Å,这样构成正方形平面(NiN4)并呈低自旋的顺磁构型。化合物显示了同[Ni5(μ-tpda)4(NCS)2]类似的磁性,即在化合物中两末端Ni(II)仍存在反铁磁性的作用。 相似文献
200.
WEI Zhiyi LEE Wingkee WONG Saipeng YU Zhenxin HUANG Xuguang 《Chinese Journal of Lasers》1995,4(1):1-8
InverstigationofSelf-StartingforSelf-Mode-LockedTi:SapphireLaserInverstigationofSelf-StartingforSelf-Mode-LockedTi:SapphireLa... 相似文献