和频与差频振动光谱实验构型的分析模拟

实验构型分析是定量分析和频振动光谱的基础.变换实验构型,不仅要考虑某一振动模式信号强度的大小,还要考虑不同构型下的信号检测效率.现有的和频振动光谱实验构型分析主要考虑前者.本文探讨实验构型分析中所涉及的信号检测效率问题,模拟在共向式和频(差频)及对射式和频(差频)振动光谱实验中选取何种实验构型对采集信号光更加合理有效.利用相干光学过程能量守恒和动量守恒原理,分析了入射角及入射光频率等因素对信号出射角的影响,并模拟了信号出射角与入射角及入射光频率的关系,得到了可选的入射角组合最多、出射角随入射光频率变化最小的实验构型.结果表明,和频振动光谱采取共向式实验构型,差频振动光谱采取对射式实验构型,有利于信号采集,进而有利于用实验构型分析方法对和频(差频)振动光谱进行定量研究.     

电解沉积压电频移分析的理论与验证

提出了控制电位电解和恒电流电解两类电解沉积的压电频移分析法测定的理论公式,用实验结果验证了它的正确性.     

频移滴定的理论与应用

压电传感元件的特点是检测灵敏度高,但到80年代才成功用于液相,本文讨论压电晶振用于溶液中微量分析——频移滴定的理论及其在酸碱、沉淀、络合和氧化还原各类滴定中的应用,所提出的新型微量分析体系与经典的电导滴定等相比,具有优点.     

氨基酸分子的光学活性和频效应

用带限制场Hartree-Fock (RHF/6-311++G^**)从头算的方法进行分子构型优化, 单激发态组态相互作用(CIS/6-311++G^**)计算各种需要的相关数据; 应用态求和理论, 以长度偶极矩和速度偶极矩两种形式模拟了一系列氨基酸离子的光学活性和频效应(OA-SFG)光谱. 结果表明速度偶极矩计算得到的一系列氨基酸离子的和频效应光谱强度顺序能很好地与实验相吻合, 而长度偶极矩形式计算得到的结果与实验不吻合. 引起这两种形式和频效应光谱理论计算结果差别的原因是由于长度偶极矩形式具有原点敏感性, 而速度偶极矩没有. 速度偶极矩方法更适用于分子光学活性和频效应的模拟.     

利用压电频移分析法测定硫

1　引言硫是人体必需的元素之一,也是蛋白质等许多具有生物活性物质的重要组成元素。硫与人体健康的关系十分密切,硫的医疗价值越来越引起人们的重视,因此硫的测定具有重要意义。对于硫离子的测定,提出了包括极谱分析法[1]、电位分析法[2]、分光光度法[3]等多种分析方法。...     

化学频移法——原理与实例

本文提出了基于化学反应与压电传感相结合的化学频移法,导出了相应的理论公式。证明化学反应产生的频移遵循公式△f=-4.6×10~6hmf~2Dδ~(-1)tkC_A,式中f,h为晶体基频及泛频阶次,m,D为感应物克式量及扩散系数,δ扩散层厚,t响应时间,C_A被测物浓度,k为与化学反应计量关系有关的系数。本文为溶液中微/痕量组分测定开辟了新的方法体系,以安乃近为实例做了应用报道。     

利用压电频移法测定水中的痕量亚硝酸盐

提出了利用压电频移法测定亚硝酸盐的方法。方法以碘离子与亚硝酸根之间的氧化还原反应为依据，通过测定由反应生成的碘所引起的压电晶体频率的变化，在被萃取水相中亚硝酸盐浓度为０．００９￣２．３ｍｇ／Ｌ范围内，频移值与浓度成正比：ΔＦ＝５．８＋２．５×１０＾３Ｃ（ｍｇ／Ｌ），ｒ＝０．９９０１。方法简便，用于天然水中亚硝酸盐的测定，结果令人满意。     

介电常数对Stokes频移时间相关性的影响

基于连续介质理论,利用溶剂化能计算了香豆素水溶液单球孔穴模型的Stokes频移响应函数. 将水的介电谱实验数据拟合进而得到介电常数理论公式, 并基于此计算了相关函数. 在考虑了延迟时间后, 相关函数的理论计算结果与实验吻合. 考虑到低频响应在溶剂化驰豫中的重要性, 考察了低频极化对响应函数的影响.     

羰基化合物还原偶联为频呐醇反应的研究新进展

综述了近几年来羰基化合物还原偶联为频呐醇反应的研究新进展．     

Communication: vacuum ultraviolet laser photodissociation studies of small molecules by the vacuum ultraviolet laser photoionization time-sliced velocity-mapped ion imaging method

We demonstrate that the vacuum ultraviolet (VUV) photodissociation dynamics of N(2) and CO(2) can be studied using VUV photoionization with time-sliced velocity-mapped ion imaging (VUV-PI-VMI) detection. The VUV laser light is produced by resonant sum frequency mixing in Kr. N(2) is used to show that when the photon energy of the VUV laser is above the ionization energy of an allowed transition of one of the product atoms it can be detected and characterized as the wavelength is varied. In this case a β parameter = 0.57 for the N((2)D°) was measured after exciting N(2)(o(1)Π(u), v(') = 2, J(') = 2) ← N(2)(X(1)Σ(g) (+), v(") = 0, J(") = 1). Studies with CO(2) show that when there is no allowed transition, an autoionization resonance can be used for the detection of a product atom. In this case it is shown for the first time that the O((1)D) atom is produced with CO((1)Σ(+)) at 92.21 nm. These results indicate that the VUV laser photodissociation combined with the VUV-PI-VMI detection is a viable method for studying the one-photon photodissociation from the ground state of simple molecules in the extreme ultraviolet and VUV spectral regions.     

双光子共振四波差频产生的真空紫外激光特性研究

The character of tunable Vacuum-Ultraviolet（VUV）laser generated by two-photon resonant four wave difference frequency mixing in Xenon was studied. The intense VUV laser was generated in the wavelength range of 151-171 nm using 6P［1/2,0］level of Xe atom as the two-photon resonant state. The pulse intensity of VUV laser was estimated to be 0.2 μJ,and the conversion efficiency relative to the wavelength-fixed laser was determined to be 0.1%. The line width of VUV laser was found to be 0.3 cm-1 from the laser-induced fluorescence spectrum of A-X（0,0）rotational line profiles of jet-cooled CO,which was much broader than those of the two employed dye lasers（0. 1 cm-1）,mainly due to the saturation broadening of Xe level by intense laser field. The dependencies of VUV intensity on Xe pressure and two dye laser intensities were also investigated in this experiment.     

Gas-phase formation of large neutral alkaline-earth metal tryptophan complexes

We report on the first observation of isolated large neutral metal amino acid complexes such as Trp(n)Me(k), with Me=Ca, Ba, Sr, cluster combinations covering n=1...33, k=0..2 and masses beyond 6500 u. The cluster beam is generated using UV laser desorption from a mixed powder of alkaline-earth metal salts and tryptophan inside a cluster mixing channel. The particles are detected using VUV photoionization followed by time-of-flight mass spectroscopy. The enhanced stability of metal amino acid clusters over pure amino acid clusters is substantiated in molecular dynamics simulations by determining the gain in binding energy related to the inclusion of the metal atoms.     

Infrared-vacuum ultraviolet pulsed field ionization-photoelectron study of C2H4(+) using a high-resolution infrared laser

The infrared (IR)-vacuum ultraviolet (VUV)-pulsed field ionization-photoelectron (IR-VUV-PFI-PE) spectrum for C2H4(X1A(g), v11 = 1, N'(Ka'Kc') = 3(03)) in the VUV range of 83,000-84,800 cm(-1) obtained using a single mode infrared laser revealed 24 rotationally resolved vibrational bands for the ion C2H4(+)(X2B(3u)) ground state. The frequencies and symmetry of the vibrational bands thus determined, together with the anharmonic frequency predictions calculated at the CCSD(T)/aug-cc-pVQZ level, have allowed the unambiguous assignment of these vibrational bands. These bands are mostly combination bands. The measured frequencies of these bands yield the fundamental frequencies for v8+ = 1103 +/- 10 cm(-1) and v10+ = 813 +/- 10 cm(-1) of C2H4(+)(X2B(3u)), which have not been determined previously. The present IR-VUV-PFI-PE study also provides truly rovibrationally selected and resolved state-to-state cross sections for the photoionization transitions C2H4(X1A(g); v11, N'(Ka'Kc')) --> C2H4(+)(X2B(3u); vi+, N+(Ka+Kc+)), where N'(Ka'Kc') denotes the rotational level of C2H4(X1A(g); v11), and vi+ and N+(Ka+Kc+) represent the vibrational and rotational states of the cation.     

A theoretical analysis of three-wave mixing in an optically active medium

A three-wave mixing experiment is considered in which the interacting frequencies |ω₁| (= |ω₃|) = ω, |ω₂| = ω ? Δ, and the resulting frequency is |ω_r| = ω + Δ. The effects are studied which result from circular polarization of the incident light beams, in particular within a sample of randomly oriented optically active molecules. Contributions to the induced third-order electric polarization are derived which are of first order in the magnetic dipole and electric quadrupole interactions. Cases are specifically considered where Raman-type resonances at frequency Δ can occur (CARS), or two-photon resonances at frequency 2ω. The possibility is discussed of investigating Raman optical activity and two-photon optical activity by measuring circular intensity differences and changes of polarization of the resulting beam of frequency ω + Δ. Some higher-order effects are also briefly mentioned. Use is made of graphs, as defined by Ward.     

分子扭转振动固有频率与链烷烃的定量-结构性质相关研究

将链烷烃分子拓扑图近似地看作一个多自由度扭转振动系统，分子中的原子或 原子基团代表系统中的质点，化学键代表连续各质点的弹簧，用相对原子量反映质 点的质量大小，用键能反映弹簧的刚度，用机械振动理论方法计算各阶固有频率ω _i，用其中的基频ω_0和总频∑ω_i作为链烷烃分子结构信息指数，建立结构-性 质相关模型：P_i = aω_0 + b∑ω_i + c。将该模型用于链烷烃分子的15种物理 化学性质的相关分析，其相关性系数均在0.9190与1.0000之间。     

Formation, detection, and stability studies of neutral vanadium sulfide clusters

Neutral vanadium sulfide clusters are generated by the reaction of seeded hydrogen sulfide in a helium carrier gas with laser ablated vanadium metal within a supersonic nozzle. The exiting clusters are expanded into a vacuum in a molecular beam and are ionized by both ultraviolet (UV) and vacuum UV (VUV) laser radiation. The generated ions are detected by a time of flight mass spectrometer. With single photon ionization (SPI) employing VUV (118 nm) radiation, sulfur rich clusters (V(m)S(n), n>m+1) and hydrogen containing clusters (V(m)S(n)H(x), x>0) are observed. With multiphoton ionization (MPI) through nanosecond UV (193 nm) radiation, these sulfur rich and hydrogen containing clusters cannot be observed, indicating severe fragmentation generated by MPI and the importance of SPI in determining the neutral vanadium sulfide cluster distribution. With MPI through femtosecond UV (226 nm) radiation, a few sulfur rich and hydrogen containing clusters are detected, but most clusters observed by SPI are still undetected even by femtosecond MPI. Density functional theory calculations are applied to optimize energies and structures of the clusters with m=1-3 and n=0-7. The experimental results are well interpreted based on the calculations. The calculated and experimental results for vanadium sulfides are compared with those of vanadium oxides in literature.     

Vacuum ultraviolet-infrared photo-induced Rydberg ionization spectroscopy: C-H stretching frequencies for trans-2-butene and trichloroethene cations

We have demonstrated the two-color vacuum ultraviolet (VUV)-infrared (IR) photoinduced Rydberg ionization (PIRI) experiment. Trichloroethene (ClCH=CCl2) and trans-2-butene (trans-CH3CH=CHCH3) were prepared in Rydberg states in the range of effective principal quantum number n* approximately 7-93 by VUV excitation prior to IR-induced autoionization. The observed VUV-IR-PIRI spectra are found to be independent of n*, suggesting that the electron Rydberg orbital is conserved, i.e., the Rydberg electron is behaving as a spectator during the excitation process. The observed IR active C-H stretching vibrational frequencies nu12+ = 3072+/-5 cm(-1) for ClCH=CCl2+ and nu23+ =2908+/-3 cm(-1), nu25+ =2990+/-10 cm(-1) and nu30+ =3022+/-10 cm(-1) for trans-CH3CH=CHCH3+ are compared with predictions based on ab initio quantum-chemical procedures and density functional calculations.     

共沉淀法合成稀土正磷酸盐(La,Gd)PO4:RE3+(RE=Eu,Tb)及其真空紫外光谱特性

采用共沉淀法制备了稀土正磷酸盐荧光粉(La,Gd)PO4:RE3+(RE=Eu,Tb).红外光谱分析发现GdPO4的红外光谱吸收峰与LaPO4一致,只是峰位向高波数方向移动.(La,Gd)PO4:RE3+的真空紫外光谱特性研究表明,Gd3+在能量传递过程中起中间体作用.XPS研究揭示,LaPO4的价带由O2-的2p能级构成,而GdPO4的价带则是由O2-的2p能级和Gd3+的4f能级共同构成.     

High-resolution Absorption Spectra of Acetylene in 142.8-152.3 nm

The absorption spectra of acetylene molecules was measured under jet-cooled conditions in the wavelength range of 142.8-152.3 nm,with a tunable and highly resolved vacuum ultraviolet (VUV) laser generated by two-photon resonant four wave difference frequency mixing processes. Due to the sufficient vibrational and rotational cooling effect of the molecular beam and the higher resolution VUV laser, the observed absorption spectra exhibit more distinct spectral features than the previous works measured at room temperature. The major three vibrational bands are assigned as a CC symmetry stretching vibrational progress (v2=0-2) of the C1Ⅱu state of acetylene.The observed shoulder peak at 148.2 nm is assigned to the first overtone band of the trans-bending mode v4 of the C1Ⅱu state of acetylene. Additionally,the two components, 420 (μ1Ⅱu) and 420(к1Ⅱu),are suggested to exhibit in the present absorption spectra,due to their Renner-Teller effect and transition selection rule.All band origins and bandwidths are obtained subsequently,and it is foundthat bandwidths are broadened and lifetimes decrease gradually with the excitation of vibration.