Near UV Spectra of Phenoxyacetic Acid and Phenoxypropanoic Acid

Abstract

The secondary transition of the benzene molecule lies towards 250-260 nm. It is electronically forbidden because of the D_6h symmetry of the molecule. The intensity of the transition is low (?_max = 220; medium : cyclohexane) and very sensitive to interactions with the surrounding parts of the molecule likely to perturb the symmetry. Substituents distort all the more the symmetry as their orbitals couple with the orbitals of the x system. They increase the intensity of the transition according to a vector scheme taking into account the positions of the substituents around the nucleus, and the strength of their coupling (SKLAR). ^7-14It has been shown that the too much qualitative SKLAR's approach could be superseded by the much more quantitative and more accurate NVM (New Vector Model) l5 grounded on MNDO calculations, or the IVM (Interaction Vector Model) using a more empiric approach.     

Matrix Isolation Infrared Spectra of Methylacetate III. UV-Induced Z→E photorotamerisation of Methylacetate in Argon Matrices

Abstract

Broadband UV-irradiation of methylacetate isolated in argon matrices causes rather strong modifications to appear in the IR spectrum. Evidence was obtained for a photochemical interconversion of the stable Z-conformer into the less stable E-conformer followed by photolytic decomposition of the latter into stable products. Most of these products could be identified from their IR absorptions. The reverse E→Z interconversion is a thermal process with an activation energy of about 10 kJmole^?1. A normal coordinate analysis based on a transferable valence force field obtained from the literature allowed to assign approximate IR frequencies of E-methylacetate.     

基质隔离红外光谱结合理论计算研究第五族金属原子和硫化氢反应

利用基质隔离红外光谱结合理论计算,研究了激光溅射获得的第五族金属原子和硫化氢分子的反应. 结果表明金属原子插入H₂S的H-S化学键形成HMSH分子(M=V,Nb,Ta). 对Nb和Ta该HMSH分子重排为H₂MS分子. HMSH分子和H₂S进一步反应生成H₂M(SH)₂分子. 通过D₂S和H₂³⁴S同位素标定确定了产物的分子结构,同时我们用DFT(B3LYP和BPW91)理论计算预测了产物分子的能量、结构和振动频率. 通过DFT IRC计算研究了第五族金属原子和₂S分子的反应机理. HVSH分子通过光照解离为VS和H₂,然后通过退火可以发生VS和H₂复合反应. 计算表明HVSH释放H₂需要16.9 kcal/mol的活化能及吸热13.5 kcal/mol.     

Vibrational Spectra of cis and trans Oxalyl Fluoride and Their Site-Selective IR-Induced Rotamerization in an Argon Matrix

A cis/trans equilibrium mixture of matrix-isolated oxalyl fluoride was irradiated with a narrowband tunable IR source in the 2nu (CO) spectral region (3680-3710 cm(-1)). Rotamerization of cis into trans and vice versa was achieved (even site selective) by selective IR pumping. The experiments strongly aided a detailed IR analysis of both rotamers. For a complete vibrational analysis, low-temperature Raman measurements were also performed. With the exception of the torsional vibration of cis oxalyl fluoride, all the fundamentals of both rotamers have been observed. Copyright 2000 Academic Press.     

Rotational Spectra of Argon Acetone: A Two-Top Internally Rotating Complex

The rotational spectra of the argon acetone weakly bound complex was studied by pulsed jet Fabry-Perot Fourier transform microwave spectroscopy. Over 500 transitions of the complex were measured between 5.5 and 26 GHz from J=2-1 to J=12-11. The two methyl groups undergo hindered internal rotation resulting in four or five internal rotation states. The microwave transitions are within these states, resulting in a splitting of each rotational transition into four and sometimes five distinct transitions. The three-fold barrier to internal rotation is determined to be 260 cm⁻¹, 2% less than the 266 cm⁻¹ barrier in acetone itself. The structure of the complex has the argon atom above the heavy atom plane of the acetone, 3.52 Å from the CO bond and approximately in the C_s plane, which is perpendicular to the CCC plane of acetone.     

Emission Spectra of BeO in Near Ultraviolet Region

Abstract

The emission spectra of isotopic BeO molecules as excited in low-pressure arc have been photographed in the region 300–350 nm at medium dispersion. The bands have been assigned to the c³II ? a³II system. The vibrational numbering was obtained from a study of the vibrational isotope effect. Vibrational constants for involved states are derived from least-squares fits of the measured bandhead wavenumbers.     

近红外光谱分析中应考虑的几个问题

近年来红外光谱分析技术得到了迅速的发展,原因在于它能够有效地提供关于样品的定性和定量信息。但是,在进行近红外光谱分析时,应考虑样品的特征、分析实验的设计及数据处理等多方面的问题,以取得更 可靠的分析结果。     

用近红外光谱分析法测定汽油辛烷值

用近红外光谱技术测定汽油辛烷值,在高精度分光光度计上测得１２个汽油标准样品和４个未知样品的近红外区吸收光谱,建立多元统计分析模型,用逐步回归法和偏最小二乘法对模型进行校准,并将其用于未知样品的预估分析,辛烷值的分析精度达到≤±１．０。     

Two-Photon Laser-Induced Fluorescence Spectra of Argon in a Grimm-Style Glow Discharge Tube

Two-photon excited laser-induced fluorescence (LIF) spectra of argon atom were successfully observed in a Grimm-style glow discharge tube, which has widely been applied to depth profiling of the elemental composition on various film-like samples by emission spectrometry. The LIF signal of an argon atomic line at 641.63 nm was observed when the glow discharge argon plasma was illuminated by a pulsed Ti:sapphire laser radiation of 7–10 mJ/pulse at 753.39 or 795.66 nm without focusing of the laser beam.     

Matrix Line in Pulsed Electron-Nuclear Double Resonance Spectra

The intense line in Mims and Davies electron-nuclear double resonance (ENDOR) spectra due to the hyperfine interactions of an unpaired electron with distant matrix nuclei is shown to originate from a simultaneous inversion of a large number of nuclear spins by a radiofrequency pulse. Theoretical expressions describing the matrix ENDOR effect are derived and verified experimentally.     

硒杂环-金属离子在乙醇溶液中的紫外吸收光谱

研究了不同分子结构的硒杂环化合物—金属离子在乙醇溶液中的紫外吸收光谱 ,硒杂环均为苤硒脑类化合物 (piazselenoles,简称Pis) :4 ,5 benzopiazselenole(BP) ;anthra[1,2 c][1,2 ,5 ]selenadiazol 6 ,11 dione(AS) ;piazselenole(PS) ;5 methyl piazselenole(MP) ;4 ,6 diBr piazselenole(DBP) ;4 ,4 ' dipiazselenole(DP)。结果表明 :Pis随分子共轭体系增大或共轭效应增强 ,紫外吸收波长λ呈现有规律地红移 ,摩尔吸光系数ε增大 ;Sn(Ⅳ ) ,Cd(Ⅱ ) ,Cr(Ⅲ ) ,Sb(Ⅲ ) ,Fe(Ⅲ ) ,Fe(Ⅱ )及Cu(Ⅱ ) BP≥ 1均使BP的紫外吸收增强 ,Zn(Ⅱ )的影响较小。Sn(Ⅳ ) ,Cr(Ⅲ )和Sb(Ⅲ )均可使Pis的短波位置的紫外吸收增强 ,使MP于 2 33nm处的峰形变钝。     

UV照射大肠杆菌对其吸收光谱的影响

探讨了样品池溶液及分光光度计内置紫外光对大肠杆菌吸收光谱测定的影响。发现样品池溶液(2.8 mL双蒸水+0.1 mL生理盐水+0.1 mL LB培养基)较为合理,既给细菌提供了有利的生存环境,又对细胞的紫外吸收影响较小;研究同时发现在257 nm波段150 s内细胞吸收强度基本没有变化,说明内置的紫外光不会影响试验测定结果。在此基础上,研究了UV照射0,20,40,60,80,120 s大肠杆菌吸收光谱的变化情况。结果显示随着UV照射剂量的增加,大肠杆菌吸收光谱存在一个先降后升再降的现象。该现象反映了辐射中细胞损伤死亡和修复存活的生物学效应。该研究从光谱学角度探讨了UV对大肠杆菌细胞的损伤作用,对利用光谱技术研究细胞的辐射损伤、死亡和修复具有一定参考意义。     

二氧化硅凝胶玻璃基质中原位合成镍酞菁的动力学研究

实现酞菁材料化进而器件化的一个重要途径是将其引入到固相基质制备酞菁掺杂的复合材料。文章以邻苯二腈和可溶性镍盐为反应试剂,通过一定温度的热处理,采用原位合成技术在二氧化硅凝胶玻璃基质中原位合成镍酞菁,制备了复合凝胶玻璃材料, 并用紫外-可见吸收光谱表征了其制备过程。由于镍酞菁在可见光区域有明显吸收,以镍酞菁物理掺杂的复合凝胶玻璃作为参照,用670 nm处的吸光度来计算原位合成镍酞菁的量。研究了原位合成动力学,拟合出原位合成NiPc的量与加热时间的关系曲线。拟合曲线呈“S”形,与Avrami-Erofeev公式相符。由此推导出在180, 185, 190, 195和200 ℃时的反应级数分别是4.5, 4.5, 3.7, 3.2, 1.9。     

染料掺杂的SiO2基近紫外波段固体激光材料的研究

采用溶胶－凝胶技术技术合成了掺杂近紫外波段激光染料ＢＰＢＤ－３６５的ＳｉＯ２基因体材料,用波长为３０８ｎｍ的ＸｅＣｌ激光器件泵浦源,横向泵浦获得了峰值波长为３６４ｎｍ的激光输出。在泵浦光能量为１０ｍＪ时激光输出达到０．２０ｍＪ,转换效率为２．０％。     

酸度对模拟转铁蛋白小分子紫外差光谱的影响

通过观察酸度对模拟转铁蛋白小分子EHPG和HBED紫外差光谱的影响,结合脱铁伴清蛋白与金属离子、阴离子结合的光谱特性,推断脱铁伴清蛋白与金属离子的结合导致金属离子结合位点处酪氨酸酚羟基的去质子化,而与阴离子的结合导致阴离子结合位点处酪氨酸酚羟基的质子化.     

近红外拉曼光谱干扰特例的成因分析

一台激光拉曼光谱仪,在进行785.18 nm近红外激发测定时,出现许多不规则的干扰谱峰,发现是出光滤光片(Notch filter)的带阻特性不良造成的.并就带阻滤光片的吸收光谱进行了分析和探讨.     

UV Phoelectron Spectra of Biological Xanthines: Theophylline,Theobromine and Caffeine

Photoelectron spectra of three natural methylated xanthines are discussed by qualitative considerations on the constitutive subunits and the methylation effects. The first band in all three cases can be assigned to enaminic molecular subunit, as in uracil; also the positions of the lone pairs of nitrogen and oxygen atoms are discussed.     

Reflection and Absorption Spectra of Fluorite in the UV Spectral Region

We have calculated the R(E) and ₁(E) spectra from the theoretical ₂(E) spectra of five models in the region 8–27 eV and the ₂(E) and ₁(E) spectra from the experimental R(E) spectrum in the region 6–35 eV. The results are compared with the known theoretical ₂(E) spectra of five models. The basic features of all of the R(E), ₂(E), and ₁(E) spectra have been revealed. It is established that the experimental R(E) spectrum and the ₂(E) and ₁(E) spectra calculated with the use of experimental data are in good agreement with the results of theoretical calculations for the models of ₂(E). On the basis of the known theoretical calculations of the fluorite zones, a scheme of the nature of the principal maxima of R(E) and ₂(E) is suggested.     

发射光谱研究氩气/空气混合气体介质阻挡放电能量传递过程

使用水电极介质阻挡放电装置,对比氩气与氩气/少量空气的混合气体以及空气与空气/少量氩气的混合气体放电的发射光谱,研究了氩气与空气相混合时气体放电中的能量传递过程。实验发现, 当氩气中加入少量的空气时,氩原子谱线均变弱,说明空气中的氮分子对氩原子的各激发态具有猝灭作用。并且随着空气含量的增加,各谱线变弱的速率不同。越是与氮分子的激发电位接近的氩原子的激发态被猝灭的作用越明显。另一方面,当空气中加入少量氩气时,发现氮分子第二正带系和氮分子离子第一负带系的谱线均被增强。说明在空气/少量氩气放电中,氮分子的激发由于亚稳态氩原子的潘宁激发传能而增强。因此在氩气/空气混合气体放电中,气体成分及比例影响放电的发光特性和能量传输特性。     

白芍紫外指纹图谱共有峰率和变异峰率双指标序列分析

采用共有峰率和变异峰率双指标序列分析法对不同产地、不同采集年份的白芍样品及相近植物赤芍、丹皮样品进行了定量评价。白芍等紫外指纹图谱双指标序列分析结果显示,相近产地的3份白芍B2,B3,B4具有最相近关系, 它们之间共有峰率大于70%,变异峰率都小于33.33%。而不同产地的白芍之间存在着较明显的差异,B1,B5与B2,B3,B4之间的共有峰率小于60%,与B6的共有峰率小于57%。同一产地不同年份的白芍B1,B5之间存在着较大的差异,它们之间的共有峰率仅为44.4%, 变异峰率高达100%。该法可以对至少2个样品进行定量评价,克服了多种中药鉴别方法只能进行真伪鉴别、产地鉴别的局限性,为中药质量的准确定量评价提供了一种新方法。