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101.
An accurate potential energy surface for the ground electronic state of SH3 system has been constructed with 41,882 high level ab initio energy points and the neural network fitting method. The time-dependent wave packet method has been used to calculate the first state-to-state differential cross sections for the title reaction up to 1.2 eV in full dimensions, based on the reactant–product decoupling scheme. It is found that the majority of H2S are produced in the ground vibrational state, with a large fraction of available energy for the reaction ending up as product translational motion. The differential cross sections at the threshold energy are dominated by a very narrow peak in the backward direction. With the increase of collision energy, the width of the angular distribution increases considerably, which is a typical feature of a direct reaction via abstract mechanism, similar to the H2 + OH → H2O + H reaction. © 2018 Wiley Periodicals, Inc. 相似文献
102.
使用界面和频振动光谱(SFG-VS)测量了空气/水界面三甲基硅烷表面活性剂Silwet L-77的C-H伸缩振动光谱.这些光谱峰主要是在2905 cm-1附近属于-Si-CH3基团的对称伸缩(SS)振动,在2957 cm-1的主要是-Si-CH3基团反对称伸缩(AS)振动,以及明显较弱的在2880 cm-1附近的属于-O-CH2-基团的对称伸缩(SS)振动.通过比较低于和高于临界聚集或胶束浓度(CAC)的SFG-VS偏振光谱显示Silwet L-77分子的C-H基团取向在不同的界面密度下变化很小.SFG-VS测量的吸附等温线表明Silwet L-77分子在空气/水界面没有形成所谓的双层结构的迹象.Silwet L-77分子在空气/水界面的Gibbs吸附自由能为-42.2±0.8 kJ/mol,表明该分子具有很强的表面吸附能力. 相似文献
103.
Ruimin Wang 《Molecular physics》2018,116(2):171-178
Excess electrons play a key role in many of the properties of Titanium dioxide (TiO2). Understanding their behaviour is important for improving the performance of TiO2 in energy-related applications. Here, we describe a DFT + U study of the locations of the unpaired electron (UPE) on rutile TiO2(110) (R-TiO2(110)) surface and H2O/R-TiO2(110) surface. Our results show that the subsurface are preferred with R-TiO2(110) surface. In contrast to previous studies, we find that the UPE tends to migrate to the surface H2O-Ti5c (the five-coordinated titanium (Ti5c) at surface with H2O adsorption) with the increasing of H2O coverage and UPE concentration. In addition, we have shown that the UPE plays an important role in the O-H bond dissociation and other important elementary reactions in photo-catalytic H2O dissociation on R-TiO2(110) such as H, OH and H2 desorption. Specifically, it enhances the O-H bond dissociation, as well as H and H2 desorption from bridging hydroxyl and Ti5c-OH (the Ti5c with OH adsorption), but hinders the OH and H desorption from Ti5c. We believe our results afford a further understanding of the adsorbent dependent UPE migration, and the role of UPE in the surface reactions. 相似文献
104.
Wen-Jin Yin Bo Wen Chuanyao Zhou Annabella Selloni Li-Min Liu 《Surface Science Reports》2018,73(2):58-82
As a prototypical photocatalyst, TiO2 is a material of scientific and technological interest. In photocatalysis and other applications, TiO2 is often reduced, behaving as an n-type semiconductor with unique physico-chemical properties. In this review, we summarize recent advances in the understanding of the fundamental properties and applications of excess electrons in reduced, undoped TiO2. We discuss the characteristics of excess electrons in the bulk and at the surface of rutile and anatase TiO2 focusing on their localization, spatial distribution, energy levels, and dynamical properties. We examine specific features of the electronic states for photoexcited TiO2, for intrinsic oxygen vacancy and Ti interstitial defects, and for surface hydroxyls. We discuss similarities and differences in the behaviors of excess electrons in the rutile and anatase phases. Finally, we consider the effect of excess electrons on the reactivity, focusing on the interaction between excess electrons and adsorbates. 相似文献
105.
袁勤勤 杨正 李仁忠 Wesley J. Transue 李志鹏 江凌 Niranjan Govin Christopher C. Cummins 王学斌 《化学物理学报》2018,31(4):463-470
Gaseous dibenzo-7-phosphanorbornadiene P-sulfide anions APS-(A=C14H10 or anthracene) were generated via electrospray ionization, and characterized by magnetic-bottle photoelectron spectroscopy, velocity-map imaging (VMI) photoelectron spectroscopy, and quantum chemical calculations. The electron affinity (EA) and spin-orbit (SO) splitting of the APS· radical are determined from the photoelectron spectra and Franck-Condon factor simulations to be EA=(2.62±0.05) eV and SO splitting=(43±7) meV. VMI photoelectron images show strong and sharp peaks near the detachment threshold with an identical electron kinetic energy (eKE) of 17.9 meV at three different detachment wavelengths, which are therefore assigned to autodetachment from dipole-bound anion states. The B3LYP/6-31++G(d,p) calculations indicate APS· has a dipole moment of 3.31 Debye, large enough to support a dipole-bound electron. 相似文献
106.
We have investigated the photoinduced decomposition of formaldehyde (CH2O) on a rutile TiO2(100)-(1×1) surface at 355 nm using temperature-programmed desorption. Products, formate (HCOO-), methyl radical (CH3·), ethylene (C2H4), and methanol (CH3OH) have been detected. The initial step in the decomposition of CH2O on the rutile TiO2(100)-(1×1) surface is the formation of a dioxymethylene intermediate in which the carbonyl O atom of CH2O is bound to a Ti atom at the five-fold-coordinated Ti4+ (Ti5c) site and its carbonyl C atom bound to a nearby bridge-bonded oxygen (Ob) atom, respectively. During 355 nm irradiation, the dioxymethylene intermediate can transfer an H atom to the Ob atom, thus forming HCOO- directly, which is considered as the main reaction channel. In addition, the dioxymethylene intermediate can also transfer methylene to the Ob row and break the C-O bond, thus leaving the original carbonyl O atom at the Ti5c site. After the transfer of methylene, several pathways to products are available. Thus, we have found that Ob atoms are intimately involved in the photoinduced decomposition of CH2O on the rutile TiO2(100)-(1×1) surface. 相似文献
107.
A new velocity map imaging spectrometer is constructed for molecular reaction dynamics studies using time-resolved photoelectron/ion spectroscopy method.By combining a kHz pulsed valve and an ICCD camera,this velocity map imaging spectrometer can be run at a repetition rate of 1 kHz,totally compatible with the fs Ti:Sapphire laser system,facilitating time-resolved studies in gas phase which are usually time-consuming.Time-resolved velocity map imaging study of NH3 photodissociation at 200 nm was performed and the time-resolved total kinetic energy release spectrum of H+NH2 products provides rich information about the dissociation dynamics of NH3.These results show that this new apparatus is a powerful tool for investigating the molecular reaction dynamics using time-resolved methods. 相似文献
108.
We study the H+CH4/CD4→H2/HD+CH3/CD3 reactions using the time sliced velocity map ion imaging technique. Ion images of the CH3/CD3 products were measured by the (2+1) resonance enhanced multi-photon ionization (REMPI) detection method. Besides the CH3/CD3 products in the ground state, ion images of the vibrationally excited CH3/CD3 products were also observed at two collision energies of 0.72 and 1.06 eV. It is shown that the angular distribution of the products CH3/CD3 in vibrationally excited states gradually vary from backward scattering to sideways scattering as the collision energy increases. Compared to the CH3/CD3 products in the ground state, the CH3/CD3 products in vibrationally excited states tend to be more sideways scattered, indicating that larger impact parameters play a more important role in the vibrationally excited product channels. 相似文献
109.
We consider excitons in a two-dimensional periodic potential and study the linear response of the excitonic superfluid to an electromagnetic wave at low and high densities. It turns out that the static structure factor for small wavevectors is very sensitive to a change of density and temperature. It is a consequence of the fact that thermal fluctuations play a crucial role at small wavevectors, since exchanging the order of the two limits, zero temperature and vanishing wavevector, leads to different results for the structure factor. This effect could be used for high accuracy measurements in the superfluid exciton phase, which might be realized by a gated electron-hole gas, for instance, in coupled quantum wells or double layer materials. The transition of the exciton system from the superfluid state to a non-superfluid state and its manifestation by light scattering are discussed. 相似文献
110.
在CH_2~+体系的电子基态势能面上运用准经典轨线方法,研究了当碰撞能E=500 me V时,反应物分子的振动激发对H(~2S)+CH~+(X~1Σ~+)→C+(~2P)+H_2(X1_gΣ~+)反应的反应概率、反应截面和立体动力学性质的影响.分别计算了两矢量相关k-j′的P(θ_r)分布,三矢量相关k-k′-j′的P(φr)分布以及反应产物的四个极化微分截面.结果表明,产物分子转动角动量不仅在Y轴方向有取向效应,还定于Y轴的正方向.并且发现,随着振动量子数的增加,对反应体系产物分布的影响就越明显. 相似文献