Optical constants, dielectric constants, molar absorption coefficients, molar polarizability, vibrational assignment and transition moments of liquid iodobenzene between 4000 and 400 cm(-1) at 25 degrees C

This paper reports the complex refractive index, molar absorption coefficient and imaginary molar polarizability spectra of liquid iodobenzene at 25 degrees C. The imaginary molar polarizability spectrum was fitted with 184 classical damped harmonic bands to determine the integrated intensity of the individual transitions. The standard deviation of the fitted spectrum from the experimental spectrum is 0.024 cm(3) mol(-1), and the R(2) value of the fit is 0.9968 indicating that the fitted spectrum is an accurate representation of the experimental spectrum. The dipole moment derivatives with respect to the normal coordinates and transition moments were determined for 26 of the 30 fundamentals. The total intensities of the in-plane and out-of-plane fundamentals were compared to benzene and other monosubstituted benzene derivatives using the F-sum rule. It was found that the total intensity of the out-of-plane fundamentals is essentially the same for the different compounds while the total intensities for the in-plane fundamentals varies according to the electronegativities of the substituents.     

Vibrational assignment, integrated intensities of liquid toluene-d8 from 4000 to 450 cm-1 at 25 degrees C

The curvefit and vibrational assignment of toluene-d8 are presented as well as previous assignments. A total of 172 peaks are required to fit the experimental imaginary molar polarizability spectrum with CDHO bands. The R2-value is 0.9998 which indicates a near perfect fit. The area under the fitted spectrum is 0.3% larger than the area under the experimental spectrum. The integrated intensities of toluene-d8 are compared with those of toluene, benzene and several halogen substituted benzenes using the F-sum rule.     

Optical constants and integrated intensities of liquid hexafluorobenzene between 4000 and 250 cm at 25 °C

The optical constants (real and imaginary refractive indices) of hexafluorobenzene were determined at 25 °C via transmission measurements. Experimental absorbance spectra measured on a Nicolet Impact 410 FTIR were converted to imaginary refractive indices using methods described in the literature. The real refractive indices were obtained by Kramers–Kronig transformation of the imaginary refractive indices. From the complex refractive indices, the molar absorption coefficient (E_m) and complex molar polarizability spectra were calculated. The integrated intensities for the E_1u fundamentals were obtained from the areas under the bands in the spectrum. These integrated intensities are compared to those for benzene and benzene-d₆ in the literature.     

位移谐振子模型对三(2-苯基吡啶)合铱磷光光谱影响的理论研究

采用谐振子模型理论探讨了振动模式对Ir(ppy)₃配合物的磷光光谱的影响.多原子分子发射光谱的一般形式可以从两个绝热电子态之间的热振动关联函数推导出,相应地势能面之间的位移和Duschinsky转动的影响也被包含在多维谐振子模型的表达式中,所得关系式模拟出了Ir(ppy)₃较为精细的磷光发射光谱.计算结果表明T₁态到S₀态之间的0→1振动跃迁对发射光谱贡献较大,尤其振动频率小于1600 cm^-1的振动模贡献更多,配体中苯和吡啶环上C=C和C=N的呼吸振动,是Ir(ppy)₃出现肩峰的主要原因.玻耳兹曼分布使得主峰和肩峰的强度下降,并且两峰相互接近.该谐振子模型与密度泛函理论(DFT)结合,可以较好地定量描述多原子分子光物理过程的发射光谱以及详细了解光谱谱图的细节.     

Infrared intensities of liquids XXV: Dielectric constants, molar polarizabilities and integrated intensities of liquid toluene at 25 °C between 4800 and 400 cm

The main purpose of this paper is to present accurate infrared integrated intensities of liquid toluene, C₆H₅CH₃, at 25 °C. Also presented are the decadic molar absorption coefficients, E_m, the real and imaginary dielectric constants, ε′ and ε″, and the real and imaginary molar polarizabilities, ^′_m and ^″_m. Integrated intensities were determined as C_j, the area under bands in the spectrum, for all bands between 4800 and 440 cm⁻¹. The contributions from the different bands were separated by fitting the spectrum with classical damped harmonic oscillator bands. The uncertainties in the integrated intensities of most bands are estimated to be 5–10%, with the uncertainties in very weak bands and in shoulders possibly up to 100%. The intensity that should be assigned to the fundamentals is more difficult to estimate due to Fermi resonance with overtone and combination bands, and a best estimate is given. The integrated intensities of the fundamental vibrations and the corresponding transition dipole moments are summarized and are compared with literature values for the gas.     

Dipole moment derivatives with respect to the internal coordinates of benzene in the liquid and gas phases

This paper presents a comparison of the dipole moment derivatives with respect to internal coordinates in the liquid and gas phases for benzene-h(6), benzene-d(6) and benzene-d(1). The literature values of the integrated intensities of the infrared active fundamentals of the three gaseous isotopomers are used to determine the dipole moment derivatives with respect to internal coordinates, using the methods described in the previous paper for the liquid phase. As was found for the liquid phase in the previous paper, there is uncertainty surrounding the intensities of the individual CH stretching fundamentals of benzene-d(1) due to intensity sharing with active combinations. The magnitudes of the dipole moment derivatives with respect to internal coordinates in the gas phase are partial differentialmicro/ partial differentials=0.50+/-0.03DA(-1), partial differentialmicro/ partial differentialt=0.28+/-0.03, partial differentialmicro/ partial differentialbeta=0.24+/-0.01, and partial differentialmicro/ partial differentialgamma=0.65+/-0.02DA(-1), where s, t, beta and gamma are the CH stretching, and CC stretching, the HCC bending and the HCCC torsion displacements, respectively. The experimental intensities are different for the three isotopomers in the liquid and gas phases, and the calculations show that these differences are mainly due to a difference between the CH stretch dipole moment derivatives in the two phases. This difference was related qualitatively to the intermolecular interaction of the H with the pi-cloud of the nearest neighbour creating a pseudo-hydrogen bond.     

A study of the two-photon spectrum of and vibronic coupling in the first system of pyrene

The polarized, low-energy, two-photon absorption system of pyrene-h₁₀ and pyrene-d₁₀ in fluorene and biphenyl host crystals at 4.2 K has been measured and analyzed to provide firm symmetry assignments. Good agreement was found for the energies of the two-photon band positions in a heptane matrix recorded using a site-selective technique. The transition has A_g vibronic symmetry being induced by single quanta of several b_2u fundamentals; very short progressions in some a_g modes were observed. Vibronic coupling involving a_g modes in the one-photon spectra has been examined. Relative line intensities have been measured for seven fundamentals in absorption and fluorescence together with some overtones and binary combinations. First-order Herzberg—Teller theory can account for these intensities and the intensities in the two-photon spectrum. The vibronic coupling is of medium strength, and plays an important role in determining the intensities of the bands in the spectrum because the allowed component of the transition is weak. In the one-photon, the strength of the coupling is weaker in a biphenyl than in a heptane matrix; in the former case, it is assumed that there is a transition dipole interaction that acts to transfer intensity from the guest to the host in such a way as to reduce the transition moment to the pyrene “lending” state involved in the vibronic coupling.     

High-resolution laser spectroscopy of the AΠu-XΠg system of Br2

The laser excitation spectrum of the Br₂⁺ molecular ion was observed at rotational resolution for the first time, with the ions being generated by Penning ionization. In contrast to Cl₂⁺ and F₂⁺ but in agreement with recent theoretical work, no vibrational or rotational perturbations are observed. The data from a number of vibrational bands are fitted simultaneously to give reliable estimates of the Dunham rotational and vibrational constants. This fit indicates that the vibrational numbering used in previous studies should be increased by 1 in the upper state.     

A valence force field for phenylalkynes Part II. Fundamental frequencies of phenylacetylene and tolane and molecular conformation of tolane in solution

The Raman and infrared spectra of tolane solutions and solid were recorded in the range 3200—30 cm⁻¹. An overlay calculation of valence force field for a group of molecules (benzene, phenylacetylene, tolane and diphenyldiacetylene) was undertaken to assign the tolane and diphenyldiacetylene fundamentals. A 46-parameter force field was derived from 371 observed wavenumbers. Reasonably good fits were obtained with an average error of 7 cm⁻¹ for in-plane and 6 cm⁻¹ for out-of-plane frequencies.

The tolane conformation in solution is discussed and evidence that the most probable geometry is planar is presented. Some experimental results inexplicable in terms of the planar model were obtained, and were ascribed to the fraction of non-planar molecules present.     

Vibrational spectra and structure of chlorine substituted cyclopropanes : Part I. cis-1,2,3-Trichlorocyclopropane

The synthesis of cis-1,2,3-trichlorocyclopropane is reported. The infrared spectra have been recorded between 4000 and 400 cm⁻¹ in the polycrystalline solid phase, and between 4000 and 200 cm⁻¹ in the gas phase. The spectrum of a solution in carbon disulphide was measured from 1400 to 400 cm⁻¹. The Raman spectrum has been obtained between 4000 and 100 cm⁻¹ in the solid phase. An assignment of the fundamentals of the title compound is proposed and compared with similar molecules. The spectrum unequivocally proves the C_JV structure of the molecule.     

Dipole moment derivatives and integrated intensities for the vibrational transitions of N2 … HF

The integrated intensity of vibrational transitions depends on the magnitude of the derivatives of the dipole with respect to nuclear motion. These derivatives are usually obtained by time-consuming ab initio calculations. In this paper we apply a long-range model, based on distributed schemes for describing the charge densities and polarizabilities of molecules, to the prediction of dipole derivatives and infrared intensities for the N₂ … HF complex. The results are found to agree qualitatively with full ab initio self-consistent field calculations. © 1996 by John Wiley & Sons, Inc.     

溶剂效应和取代基效应对2-(2-氨基苯基)苯并噻唑光谱性质及激发态分子内质子转移的影响

合成了多种2-(2-氨基苯基)苯并噻唑(APBT)氨基氢原子被供电子及吸电子基团取代的衍生物, 并用紫外光谱﹑荧光光谱等方法和密度泛函理论(DFT)计算研究了溶剂效应和取代基效应对衍生物的光谱性质及激发态分子内质子转移(ESIPT)的影响规律. 结果表明, 相比于非极性溶剂环己烷, 随溶剂极性的增加及APBT-溶剂分子间氢键的形成, APBT的紫外-可见最大吸收峰和荧光最大发射峰均发生了一定程度的红移, 并对APBT的ESIPT产生了影响. 在APBT分子的氨基氮原子上引入不同的吸电子或斥电子取代基, 对氮原子的电荷性质有较大的影响. 在环己烷溶剂中, 甲基取代后的APBT仅有单重荧光发射峰, 体系未发生ESIPT过程; 而COCH₂Cl等吸电子基团能促进APBT的ESIPT, 其荧光发射光谱出现了明显的双重峰, 表明体系发生了激发态分子内质子转移反应. 量子化学的理论计算较好地验证了光谱实验结果.     

Vibrational spectroscopic study of pyrrole and its deuterated derivatives: comparison of the quality of the applicability of the DFT/Becke3P86 and the DFT/Becke3LYP functionals

The aim of our work is a reassignment of the vibrational spectra of pyrrole based on high-level quantum-chemical calculations. This is a continuation of our earlier works on one side of pyrrolydine and N-methylpyrrolidine and on the other side of five-membered ring parent molecules with two-ring nitrogens.

Infrared and Raman spectra are reported for the isotopic species of pyrrole, 1-deuteropyrrole and pentadeuteropyrrole.

The molecular structure and the harmonic force field were calculated applying the ab initio density functional theory (DFT) level with both the Becke3P86 and the Becke3LYP functionals with the 6-311G(d,p) basis set. The force fields were fitted to the experimental fundamentals using in both cases eight scale factors. Though some scaled frequencies show larger deviations from the experimental ones, the percentage deviations of the calculated frequencies from the experimental ones are less than 1.0% for pyrrole and less than 1.2% for the deuterated derivatives in the case of both applied functionals.     

Ab initio calculations of stretching vibrational transitions for the linear molecules HCN, HNC, HCCF and HC3N up to high overtones

Accurate electric dipole moment functions have been calculated for the stretching vibrational coordinates of the linear molecules HCN, HNC, HCCF and HC₃N by means of coupled cluster theory with single and double excitation operators plus a quasi-perturbative treatment of connected triples (CCSD(T)). Combining these with anharmonic stretching vibrational wave-functions absolute IR intensities for strecthing vibrational transitions up to high overtones are obtained. For HCN, excellent agreement with experiment is observed up to 7 ν₁ + η₃ at 23047 cm⁻¹. HCCF and DCCF show unusual behavior, with the ν₂ band with origin at 2239.2 cm⁻¹ being strongest in HCCF and the ν₁ band with origin at 2645.1 cm⁻¹ being the most intense in DCCF. The Fermi resonance system 2ν₃/ν₂ of DCCF is analysed in detail. The calculated IR intensities of the stretching fundamentals of HC₃N and DC₃N, which are difficult to obtain with high accuracy, are in very good agreement with the existing experimental data.     

Dissociative ion-pair formation in collisions of fast potassium atoms with benzene and fluorobenzene

Using a crossed molecular-beam technique, electron transfer is studied in collisions of fast potassium atoms with benzene and fluorobenzene molecules. The negative fragment ions formed in the collision region are extracted by a pulsed voltage, and their masses and energy release distributions analyzed by a time-of-flight (TOF) method. The dominant fragment from C6H5F is F-. The phenyl ring fragments CH- and C2H- are also observed but with lower intensities. In the case of C6H6 the dominant anionic specie is C2H-. The kinetic-energy release distributions of the various fragments are derived from the width and shapes of the TOF peaks in the spectrum.     

Studies of the Auger spectrum from the (100) surface of GaAs using positron annihilation induced Auger electron spectroscopy

Measurements of the first high-resolution positron annihilation induced Auger spectrum from GaAs(100) are presented. The spectrum displays six As and three Ga Auger peaks below 110 eV, including a strong As M_4,5VV peak at 28 eV and a less intense Ga M_2,3M_4,5M_4,5 peak at 53 eV. The Auger peak intensities are used to obtain experimental annihilation probabilities for relevant core-level electrons. Experimental results are compared with first-principles calculations of positron surface states and annihilation characteristics of surface trapped positrons.     

A charge–charge flux–dipole flux decomposition of the dipole moment derivatives and infrared intensities of the AB3 (A = N,P; B = H,F) molecules

The quantum theory of atoms in molecules (AIM) has been used to decompose dipole moment derivatives and fundamental infrared intensities of the AB₃ (A = N,P; B = H,F) molecules into charge–charge flux–dipole flux (CCFDF) contributions. Calculations were carried out at the MP2(FC)/6-311++G(3d,3p) level. Infrared intensities calculated from the AIM atomic charges and atomic dipoles are within 13.8 km mol⁻¹ of the experimental values not considering the NH₃ and PH₃ stretching vibrations for which the experimental bands are severely overlapped. Group V atomic dipoles are very important in determining the molecular dipole moments of NF₃, PH₃ and PF₃ although the atomic charges account for almost all of the NH₃ molecular moment. Dipole fluxes on the Group V atom are important in determining the stretching band intensities of all molecules whereas they make small contributions to the bending mode intensities. Consideration of dipole flux contributions from the terminal atoms must also be made for accurately describing the intensities of all these molecules. As expected from a simple bond moment model, charge contributions dominate for most of the NH₃, NF₃, and PF₃ dipole moment derivatives and intensities. Charge flux and dipole flux contributions are very substantial for all the PH₃ vibrations, cancelling each other for the stretching modes and reinforcing one another for the bending modes.     

Laser irradiation induced spectral evolution of the surface-enhanced raman scattering (SERS) of 4-<Emphasis Type="Italic">tert</Emphasis>-butylbenzylmercaptan on gold nanoparticles assembly

The spectral evolution of the surface-enhanced Raman scattering (SERS) of 4-tert-butylbenzylmercaptan (4-tBBM) on gold nanoparticles assembly under laser irradiation is reported. The relative intensities of typical peaks in the spectrum of 4-tBBM gradually change with irradiation time. Comparison of the rate of spectral changes under several experimental conditions indicates that the surface plasmon resonance (SPR) induced heat in the gold nanoparticles assembly is the origin of the spectral evolution. During the process of self-assembly, 4-tBBM molecules do not form a compact ordered monolayer because of the spatial hindrance of the 4-tert-butyl end group. The heat induced by laser irradiation drives the 4-tBBM molecules to rearrange to a more stable orientation. Supported by the National Natural Science Foundation of China (Grant No. 20473004) and the Beijing Key Lab for Nanophotonics and Nanostructure     

γ-环糊精对二甲戊灵的包合作用

以γ-环糊精(γ-CD)为主体, 采用饱和水溶液法对客体二甲戊灵进行包合. 采用紫外光谱以等摩尔连续变化法确定包合物的包合比为1∶1; 红外光谱证明二甲戊灵的部分苯环结构可能进入了γ-CD的空腔; 热分析结果证明包合作用提升了二甲戊灵的熔点; 粉末X射线衍射谱图中新衍射峰的出现说明形成了新物相; 扫描电镜则直观展现了包合物的外观. 以上结果均表明形成了γ-CD-二甲戊灵包合物, 其包合平衡常数K=1123.99 L/mol. 包合作用使二甲戊灵的熔点从54 ℃升至75 ℃, 溶解度提高了约11.5倍, 包合物热贮稳定性达标, 为进一步将其加工成其它水基化农药剂型提供了可能.     

含1,3-方酸苯螺旋共轭分子的设计及其电子光谱和非线性光学性质的理论研究

以量子化学半经验方法PM3优化构型为基础,利用INDO/CI方法研究了嵌入1,3-方酸的苯螺旋共轭分子的电子光谱,同时利用INDO/CI-SOS程序计算了它们的二阶非线性光学系数β_ijk和β_μ值,从而探索分子结构与电子光谱及非线性光学性质的关系.理论计算结果表明:在苯螺旋共轭分子中适当地嵌入方酸后,其二阶非线性光学系数增大.与苯螺旋共轭分子和1,3-方酸的比较表明,方酸环处于左端的体系有很好的二阶非线性光学性质,可能成为较好的光学材料.