共查询到20条相似文献,搜索用时 15 毫秒
1.
J.D. Flood E. Ehrenfreund A.J. Heeger A.G. MacDiarmid 《Solid State Communications》1982,44(7):1055-1058
A series of spin resonance experiments on samples illuminated with light at photon energies ?ω>Eg are reported. The results set an upper limit on the quantum efficiency for photoproduction of unpaired spins, γs? 2×10-7,implying that the photo-induced excited states and the photo-generated carriers are spinless and are to be associated with charged solitons. 相似文献
2.
Cis-trans isomerization of polyacetylene has been investigated by infrared spectroscopy over the temperature range 115–180°C. It is shown that isomerization is slow at 115°C and becomes rather fast above 140°C. The chemical processes during the isomerization appear to be complex, and a beginning of decomposition occurs above 140°C. 相似文献
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S. Ikehata M. Druy T. Woerner A.J. Heeger A.G. MacDiarmid 《Solid State Communications》1981,39(11):1239-1242
The proton NMR line width in undoped and AsF5 doped polyacetylene shows an abrupt change as a function of temperature, indicative of motional narrowing. The characteristic temperature for the onset of narrowing decreases with increasing AsF5 concentration. The results are discussed in terms of large amplitude librational or translational motions of the trans-(CH)x chains. The magnitudes obtained for the second moment at temperatures below and above the narrowing transition are used to obtain information on the chain packing of trans-(CH)x within the three-dimensional crystal structure. 相似文献
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Isotopically labelled (CH)x samples have been studied to probe the influence of nuclear spin diffusion on the relaxation mechanisms of polyacetylene. The results are discussed in terms of two spin species: those relaxing by direct interaction with solitons and those diffusing by mutual flip-flop towards this well relaxed core. Predictions are made for the time dependence of magnetization recovery and for the frequency dependence of long T1. 相似文献
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Electrochemical studies demonstrate that ~300 ppm of charge (equal to the number of neutral solitons in undoped -(CH)x) is removed at mid-gap. These charges are transported through the polyacetylene electrode via hopping among states at the center of the energy gap, in agreement with Kivelson's theory. From analysis of the data, we have been able to determine the soliton creation energy, Es ? 0.5eV, which is in good agreement with the theoretical value, Es = (2/π)Δ. 相似文献
8.
Y.W. Park J.C. Woo K.H. Yoo W.K. Han C.H. Choi T. Kobayashi H. Shirakawa 《Solid State Communications》1983,46(9):731-734
The temperature dependence of d.c. conductivity, thermopower and electron paramagnetic resonance (EPR) results on [CH(FeCl4)0.061]x are reported. The d.c. conductivity and thermopower measurements indicate metallic charge transport along the polyacetylene chain interrupted by the interfibril contact resistances and also ‘dragged’ primarily by the dopant ions. The initial measurements of EPR show Dysonian lineshape with very broad linewidth (ΔH ≈ 600 G at room temperature). The temperature dependence of EPR absorption intensity implies that there exist localized magnetic moments. The observed g value (g ≈ 2.03) suggests the dopant anion is in a form of (FeCl4)-. 相似文献
9.
Detailed Raman scattering data on brominated (SN)x crystals ranging in composition from (SNBr0.27)x to (SNBr0.55)x, and preliminary Raman data on [SN(ICI)0.125]x are discussed. The investigation involved a study under various conditions of temperature, pressure and levels of bromination, of the two primary Raman lines at 154 and 230 cm-1 in brominated (SN)x, which are polarized along the polymer axis direction. The analysis of the data is consistent with a model in which bromine enters the interfibrillar regions as Br-3 and the (SN)x lattice as Br2. Infrared data is also presented showing an appreciable decrease in intensity of the SN modes at 995 and 670 cm-1 on bromination. 相似文献
10.
从离散的SSH模型出发,考虑了链内的电子相互作用,以及由杂质和周围链上的荷电孤子产生的库仑势的影响,探讨了各种掺杂浓度的反式聚乙炔中孤子晶格的能谱与电子束缚态。计算结果表明:在孤子晶格的能谱中,在价带底有两条定域能级,在导带顶存在着多个电子束缚态,随掺杂浓度的升高,束缚态的局域性减弱,禁带中的孤子能级形成孤子能带。当掺杂浓度高达16.67%时,所有的电子束缚态都消失,转变为扩展态。孤子晶格的禁带宽度随着掺杂浓度的增加而增大,最高占据态与导带底之间的能隙则随之逐渐减小。孤子能带底与价带顶之间的能隙在临界浓度附近有一极大值。还讨论了电子-电子相互作用对孤子晶格能谱的影响。
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11.
Electron nuclear double resonance (ENDOR) measurements were performed on stretched films of undoped cis-rich (CH)x at 77°K. The anisotropy of the hyperfine coupling was directly observed for the first time. The anisotropy shows the π-electron character and is consistent with the assumption of the bond alternation kink in the π-electron system in undoped (CH)x. 相似文献
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From dynamical nuclear polarization experiments and ESR lineshape analysis, we show the highly mobile spins, associated with topological solitons, in undoped trans-(CH)X become gradually trapped and slowed down up on cooling. 相似文献
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A.I. Gutman L.S. Agroskin G.V. Papayan L.P. Rautian O.S. Schachnina 《Solid State Communications》1984,49(2):187-189
The technique of polarized reflection microspectroscopy was used to study anisotropy of polymeric sulfur nitride (SN)x in plasma edge region. The spectra taken from different faces of single crystals indicate the presence of strong anisotropy of interchain interaction due to orientation of the π-electron orbitals and suggest two-dimensional metallic behavior of the π-electron system in (SN)x. 相似文献
14.
Electrical resistivity of (SN)x crystal along the b-axis increases in Na ion solution by several times in a few tens of minutes. Temperature dependence of resistivity and transverse magnetoresistance at 4.2 K in Na-doped (SN)x do not change remarkably from the pristine (SN)x. These experimental results are discussed in terms of electron transfer from the dopant (Na) to (SN)x into consideration, comparing with the case of halogen doping. 相似文献
15.
Relaxation process of self-trapped polaron is investigated by a nonadiabatic molecular dynamic method. We show localized disorder due to lattice fluctuations can give rise to a tightly-bound electronic state in ultraviolet illuminated SrTiO3 crystal. This bound state is actually a self-trapped polaron in accordance with the experimentally observed large Stokes-shift. The formation of the self-trapped polaron is shown to be an ultrafast process. 相似文献
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Raman spectra of films of (CD)x at 77K show dramatic isotope effects in intensity, as well as pronounced dispersion in band profiles as the excitation wavelength is varied throughout the visible. Long series of overtone lines as well as photoluminescence are seen in spectra of the but not the isomer. 相似文献
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The electrical resistance of oriented (SN)x-films has been measured from 300 to 0.07 K. The results indicate a finite intrinsic conductivity in the direction perpendicular to the chains, supporting that (SN)x is a strong anisotropic conductor rather than a quasi-one-dimensional system. 相似文献
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Investigations of the pressure dependence of the superconducting transition temperature Tc up to 17 kbar, and of the normal conductivity up to 50 kbar are reported. It is observed that below 8 kbar, the value of Tc increases linearly with the pressure. In addition, there is a significant drop of Tc at about 9 kbar which may be due to a phase transition. 相似文献
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Brillouin scattering is used to study concentration and temperature dependence of transverse acoustic phonon frequency ωTA (110) in (KCN)x(KBr)1?x mixed crystals. Unlike pure KCN, mixed xrystals with x < 0.75 show no phase transition upon cooling, however, in these crystals we find a minimum in ωTA as a function of temperature. This minimum can be understood in terms of dynamical theory of rotation-translation coupling in molecular crystals. 相似文献
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Electron nuclear double resonance (ENDOR) measurements were performed on stretch oriented undoped cis-rich (CH)x at 4°K. The presence of the spin density which is comparable with the prediction of the soliton theory was directly observed for the first time. The maximum value of the spin density ranged from 0.11 to 0.19 depending on the choice of McConnell's constant. The form of the spin density distribution was discussed through the analysis of observed anisotropic spectral line shape using a spectrum simulation method. 相似文献