聚苯乙炔的顺、反异构和光电导的研究

聚苯乙炔(PPA)作为一种较有前途的光电导材料,目前已引起不少化学家和物理学家的广泛关注。研究表明,反式PPA比顺式具有较高的光电导^[1],而且对电子给体或受体的掺杂均具有灵敏的响应^[2],有可能被用作未来的光电器件。我们在研究顺、反式PPA光电性能的基础上^[3-5],进一步研究了顺、反异构化和它们的光电导。     

有机固体的非欧姆特性

根据电子结构观点,一般有机光导体等固体材料,可以看作是禁带宽度高达3-5eV(即光吸收限的能量)的半导体或绝缘体。因此根据热力学理论,由带间热激发所产生的载流子和由杂质能级中电子或空穴的热激发所产生的非平衡载流子,对有机固体的电导都不会有显著贡献,然而实际上对于处在高场(F≥10⁵V/cm)下的有机固体材料,可以测量到一定的电流,而此电流随外场增加呈超线性增加,即非欧姆电导性,有机固体的这种非欧姆特性对研究其电子过程是能够提供重要信息的,这就提出了有关非欧姆暗电导与光电导的物理意义的基本问题。     

份菁类有机光导材料分子结构及晶体结构与光,电导性能的关系

份菁类有机光导材料分子结构及晶体结构与光、电导性能的关系常友明（中国科学院化学研究所，北京１０００８０）有机光导材料是以光激发产生电荷载流子的有机固体材料是重要的信息功能材料。已被广泛应用于感光材料、复印机、计算机终端仪器的激光打印机。在能源日趋紧缺...     

近红外敏感的功能分离型有机光接受体系的光导性能研究Ⅱ.CGL/CTL界面能级匹配对体系光导性能的影响

功能分离型光接受体系是由载流子产生层(CGL),载流子传输层(CTL)和载流子阻挡层(UCt)组A成的一种多层光接受体系。本文合成了一系列载流子传输层材料,如吡唑啉、唑和腙的衍生物,并将上述CTL材料与酞菁类CGL材料,按一定涂布工艺制成近红外敏感(780～830nm)的多层光接受体系。通过对样品电照相性能的表征,着重讨论了CGLlCTL界面能级匹配问题及其对体系光导性能的影响。     

1,3,5-三甲苯的光电离的实验研究

利用超声分子束、真空紫外同步辐射和反射式飞行时间质谱仪开展1,3,5-三甲基苯(TMB,C9H12)的光电离和光解离研究.利用光电离质谱和光电离效率曲线,确定母体分子的电离能,主要碎片离子C9H+11和C8H+9的出现能分别为(8.32±0.03),(11.71±0.03)和(11.59±0.03)eV.根据经验公式,计算出形成C9H1+1和C8H+9的解离能(Ed)分别为(3.39±0.06)和(3.27±0.06)eV.再利用相关的热化学参数,推算出C9H1+2,C9H+11和C8H+9的标准生成焓为786.87,897.93和956.68kJ/mol.     

导电高聚物聚苯乙炔及其衍生物

聚苯乙炔(PPA)是一种具有半导体特性的高聚物。本文介绍了PPA及其衍生物的合成、化学结构与谱图及载流子的输运性质。     

αⅠ-酞菁铜蒸发膜的光导作用光谱

测量了αI-酞菁铜(PcCu)蒸发膜的吸收光谱、夹心池和表面池的光导作用光谱以及勒安指数。在PcCu蒸发膜中吸收光谱与光导作用光谱之间形状关系依赖于在表面和本体内光生载流子复合速率的比例。因为在现在测试的样品中,在表面的载流子复合速率大于在体内的。在可见区的夹心池光导作用光谱在形状上相反于吸收光谱,但表面池光导作用光谱形状介于上述两种光谱之间。在近红外区由于弱吸收本体效应起主要作用,这三种光谱形状相似。     

van der Waals团簇ArHCl的光电离研究

用同步辐射光源和光电离质谱研究了分子束中ArHClvanderWaals（vdW）团簇的光电离过程．测量结果表明，分子束中的ArHCl的浓匠与气源压力近似满足如下关系式：a（ArHCl）％＝179×10-8.首次给出了ArHCl团簇的光电高效率曲线，并测得ArHCl 的出现势为12.52±0.03eV。根据实验测量的HCl和ArHCl的电高能，计算出Ar－HCl 的解高能为022±0.03eV.用Gaussian－94w量化程序计算出解高能约为0.16eV.实验表明当团簇内的Ar电离时，ArHCl 质谱峰强度明显低于预计的强度，是由于体系电离后发生了电荷转移及解离过程．     

瞬态光电导谱研究Pt的负载对TiO2光生载流子寿命的影响

采用瞬态光电导谱研究了TiO₂的光电导衰减曲线,通过计算机拟合得到光生载流子的寿命,并考察了Pt的负载量对TiO₂光生载流子有效寿命的影响.结果表明,增大Pt的负载量,可延缓光电导的衰减趋势,从而延长TiO₂光生载流子的有效寿命,有效地降低了光生载流子的复合率.     

无金属酞菁复合膜光导作用光谱的研究

无金属酞菁复合膜光导作用光谱的研究常友明，金祥凤，邓晓东（中国科学院化学研究所，北京１０００８０）无金属酞菁是一种生成载流子的重要材料，它已广泛地应用于静电复印及激光打印中［１～２］。要增加光生载流子的量子产率，就必须了解载流子生成及复合的机制，因为...     

On the heat of formation of [C6H4]+˙

The appearance energy of the [C₆H₄]^+˙ ion from benzonitrile has been measured, using an electron monochromator. The value observed at onset, 12.54±0.03 eV, leads to a heat of formation of 1304±3 kJ mol^?1. Possible reasons for widely divergent values reported previously are proposed.     

Photochromic and luminescence properties of isomeric forms of the hydronaphthyl radicals

The optical properties of the hydronaphthyl radicals produced upon radiolysis and photolysis of rigid naphthalene solutions in boric acid at 300 K and alcohol, ether and methylcyclohexane at 77 K were investigated. The ESR, absorption and luminescence spectra of the two different isomeric forms of hydronaphthyl radicals have been observed. The estimated values of the lowest electronic transition in α- and β-hydronaphthyl radicals are, respectively: E_α = 2.42 ± 0.03 eV, E_β = 2.66 ± 0.05 eV. It has been found that a reversible photo-induced interconversion between two hydroradicals takes place as well as a dark conversion from the β- to the α-isomer. Analogous photochromic behaviour of the absorption bands of biphenyl, phenanthrene, chrysene and fluorene rigid solutions have also been identified as reversible interconversion between isomeric hydroradicals.     

Ammonia Borane,NH3BH3: A Threshold Photoelectron–Photoion Coincidence Study of a Potential Hydrogen-Storage Material

We have investigated the photoionization of ammonia borane (AB) and determined adiabatic ionization energy to be 9.26±0.03 eV for the X^{+ 2}E←X ¹A₁ transition. Although the threshold photoelectron spectrum appears at first glance to be similar to the one of the isosteric ethane, the electronic situation differs markedly, due to different orbital energies. In addition, an appearance energy AE_0K(NH₃BH₃, NH₃BH₂⁺)= 10.00±0.03 eV has been determined, corresponding to the loss of a hydrogen atom at the BH₃-site. From the data, a 0 K bond dissociation energy for the B−H bond in the cation of 71.5±3 kJ mol⁻¹ was derived, whereas the one in the neutral compound has been estimated to be 419±10 kJ mol⁻¹.     

Resonant scattering of slow electrons from naphthalene vapour

Resonant scattering of low energy electrons from naphthalene has been investigated using electron transmission spectroscopy. The transmission spectrum of naphthalene yields a value of ?0.20 ± 0.05 eV for the first electron affinity. The first and second excited states of C₁₀H^?₈ are detected at 0.96 ± 0.1 eV and 1.55 ± 0.13 eV. Resonant structure is also observed at 5.29 ± 0.1 cV and 7.55 ± 0.05 eV; it is suggested that the former resonance is the previously unidentified peak in the threshold electron excitation spectrum of Compton and co-workers.     

On the reactions of ortho-positronium with methylmaleic and methylfumaric acids

The o-Ps quenching reactions promoted by methylmaleic (citraconic) and methylfumaric (mesaconic) acids were investigated in aqueous solutions in order to compare their rate constants with those of maleic and fumaric acids. As expected, it was found that the rate constants of citraconic and mesaconic acids are almost equal and are much less than that of maleic acid, which in turn is less than that of fumaric acid. Moreover, it was ascertained that while the o-Ps quenching reactions promoted by maleic and fumaric acids seem to be diffusion controlled, the quenching reactions promoted by citraconic acid are kinetically controlled, its activation energy being 0.45±0.03 eV, which is significantly greater than the activation energy of diffusion-controlled reactions occurring in water, 0.18±0.01 eV.     

X-ray photoelectron spectra of dinitrogen chelating ligands with some transition metals

The complexes of two chelating agents, CDTA (trans-1,2-cyclohexanediaminetetraacetic acid) and EDTA (ethylenediaminetetraacetic acid), with Ni(II), Co(II) and Cu(II) are studied by means of X-ray photoelectron spectroscopy (XPS). The N1s spectrum of CDTA has two components at 398.5 (±0.2 eV) and 400.9 (±0.2 eV) while only one signal is found after coordination at 400.0±0.2 eV. EDTA shows a N1s spectrum with one component at 400.9±0.2eV. A negative shift of about -1.3eV is observed in its complexes. The results are compared with the literature data on the complexes in the solid state.     

The mechanism for diamagnetic products formation under the radiolysis of alkali nitrates

Based on optical measurements, the kinetics of peroxynitrite accumulation in alkali nitrate crystals γ-irradiated at 310 K has been investigated. The initial radiation chemical yields were calculated to be 0.60±0.05, 0.14±0.03, 0.35±0.03, 0.65±0.04 (100 eV)⁻¹ for NaNO₃, KNO₃, RbNO₃, and CsNO₃, respectively. The mechanism for the radiolysis of crystalline alkali nitrates is interpreted in terms of formation of the peroxynitrite ions and the nitrite ions from high-energy singlet and triplet excited states of the nitrate ions, respectively. These states can be generating under the radiationless transitions of electrons from the cation conductivity band into the anion conductivity band accompanied by the Auger excitation of the nitrate ions.     

Photoelectron spectrum of hypofluorous acid,HOF

The photoelectron spectrum of HOF has been obtained with He I resonance radiation. Three bands were observed, which can be interpreted by analogy to the diatomic halogens, and to the recently reported CIF. The first two bands can be identified with the out-of-plane and in-plane components of the π_g-like outermost orbital of the diatomic halogens, split by the C_s symmetry of HOF. The first ionization potential is found to be 12.69 ± 0.03 eV, in close agreement with the photoionization value 12.71 ± 0.01 eV.     

The proton formation from methane by dissociative ionization in the electron energy range of 25–40 eV

The proton formation by dissociative electroionization of methane has been investigated in the energy range of 25–40 eV. The kinetic energy-versus-appearance energy shows five different H⁺ producing processes respectively at 26.3 ± 0.2 eV, 26.9 ± 0.2 eV, 29.4 ± 0.3 eV, 32.7 ± 0.2 eV and 35.7 ± 0.5 eV. These critical energies are discussed in terms of different dissociation channels probably opened through predissociation of doubly excited states of CH⁺₄. On the high energy side of the electron energy range investigated in the present work, the proton would appear through the dissociation of the CH⁺ ion as an intermediate.     

Potential use of the activation energy value calculated from the thermoluminescence glow curves to detect irradiated food

We herein report on the calculation of the activation energy (E _a) from the thermoluminescence (TL) glow curves performed by the initial rise method that allows us to discriminate between irradiated and non-irradiated sesame seeds. E _a values of natural TL (0.68 ± 0.03 eV) and gamma-induced TL (never lower than 0.82 ± 0.02 eV) appear as a complementary criterion to be used differentiating between irradiated and non-irradiated foodstuffs with the position and the intensity of the main peak of the TL emission. In addition, E _a values taken from irradiated sesame samples at different doses (1, 5 and 10 kGy) and stored up to 15 months after being processed were compared to a ‘positive’ Spanish blend (i.e. at least one component was commercially irradiated).