Absolute line intensity measurements of hot bands for carbonyl sulfide at 12 microm

Using diode-laser spectroscopy, the intensities of 58 lines of the v(1) + v(1/2) - v(1/2) band and 36 lines of the 2v(1) - v(1) band of OCS have been measured. The corresponding band strengths S(0)(v) and the vibrational transition dipoles micro(v) have been derived through least squares fitting of these individual intensities. The band strengths values have been determined with a precision better than 2.5%.     

Ab initio studies of internal rotation barriers and vibrational frequencies of (C2H2)2, (CO2)2, and C2H2-CO2

We have performed large-scaleab initio calculations using second order Møller-Plesset perturbation theory (MP2) on the three van der Waals dimers formed from acetylene and carbon dioxide. Intermolecular geometrical parameters are reliably computed at this level of theory. Calculations of vibrational frequencies of the van der Waals modes, currently unobtainable by experimental means, give important information about the intermolecular potential and predict significant large-amplitude motion. Zero point energy contributions are shown to be vital in assessing the relative stability of conformations which are close in energy. Our studies suggest that the barrier to interconversion tunnelling in (CO₂)₂ is significantly smaller than previously inferred and is approximately the same as in (C₂H₂)₂. The reason for the rigidity of (CO₂)₂ is the difference in monomer centre-of-mass separation between ground state and transition state. We also show that, in addition to the previously observedC _2v form, the collinear form of C₂H₂-CO₂ is a local minimum on its potential energy surface.     

Thermal behavior of Cu(II)-, Cd(II)-, and Hg(II)-exchanged montmorillonite complexedwith cysteine

The thermal behavior of montmorillonite and organically modified montmorillonite, both treated with heavy metal cations [Cu(II), Cd(II) and Hg(II)], was characterized via thermal analyses (TG, DTG and DTA) combined with evolved species gas mass spectrometry (MS-EGA), and X-ray diffraction at in situ controlled temperature (HTXRD). The reactions involving Cu(II)- and Cd(II)-montmorillonite samples are mostly related to H₂O and OH loss, unlike Hg(II)-montmorillonite, where effects associated to Hg(II) loss are also present. Finally reactions related to dehydration, dehydroxylation and to organic matter decomposition can be observed in montmorillonite samples treated with cysteine.     

Energetic and topological analyses of the oxidation reaction between Mo(n) (n = 1, 2) and N2O

The interaction between molybdenum, atom, and dimer, with nitrous oxide has been investigated using density functional theory. The analysis of the potential energy surfaces for both reactions has revealed that a single molybdenum atom can activate the N--O bond of N2O requiring a small activation energy. However, the presence of several intersystem crossings between three different spin states, namely, septet, quintet and triplet states, seems to be the major constraint to the Mo + N2O reaction. Contrarily, the low-lying excited states (triplet and quintet) do not participate in the reaction between the molybdenum dimer and N2O. The latter reaction fully evolves on the singlet spin surface. Three different regions have been distinguished along the pathway: formation of an adduct complex, formation of an inserted compound, and the N2 detachment. The connection between the two first regions has been characterized by the formation of a special complex in which the N--O bond is so weakened that it could be considered as a first step in the insertion process. It has been shown that the topological changes along the pathways provide a clear explanation for the geometrical changes that occur along the reaction pathway. In summary, the detachment of the N2 molecule is found to be kinetically an effective process for both reactions, owing to the high exothermicity and consequently to the high internal energy of the insertion intermediates. However, in the case of Mo atom, the reaction should be a slow process due to the presence of spin-forbidden transitions. These results fully agree with previous experimental works.     

Vibrational frequencies and structural determinations of tert-butylacetylene

The normal mode frequencies and corresponding vibrational assignments of tert-butylacetylene (TBA) are examined theoretically using the Gaussian 98 set of quantum chemistry codes. All normal modes were successfully assigned to one of the nine types of motion (C---C stretch, CC stretch, C---H stretch, C---C---C bend, CC---C bend, CC---H bend, H---C---H bend, CH₃ rock, and CH₃ twist) utilizing the C_3v symmetry of the molecule. Calculations were performed at the Hartree–Fock, B3LYP, and MP2 levels of theory using the standard 6-311G^** basis. Theoretical results were successfully compared against available experimental data.     

M+AsF6-(M=Li,Na,K,Rb和Cs)离子对的结构和振动光谱

利用abinitio计算方法研究了AsF6-阴离子和M AsF6-(M =Li ,Na ,K ,Rb 和Cs )直接接触离子对的结构和光谱行为。结果表明,具有C3V结构三齿相互作用的M AsF6-最稳定,二齿配位的结构只有在特定条件下才可能稳定存在。当形成离子对后,阳离子与AsF6-的相互作用将改变AsF6-的结构,这其中Li 的影响最大。另外,AsF6-光谱的变化可用来指认溶液中离子的缔合和离子对的种类。     

HFSiS构型及其稳定性的理论研究

利用密度泛函理论对三线态HFSiS分子结构及其稳定性进行了详细的理论研究.在B3LYP/6-311G**水平上计算出了各驻点的优化构型、振动频率,并对各个振动模式加以归属,在同样的理论水平上进行了IRC计算;CCSD(T)结合6-311G**基组对于驻点进行单点能及相对能量的计算;根据振动模式分析来阐明三线态势能面上各驻点之间的变化,并与单线态势能面进行比较.计算结果表明,三线态HFSiS分子存在6种异构体,3HFSiS结构在动力学和热力学上都是最稳定的,实验上应该可以观测到;在两组键旋转异构体当中,结构-2具有一定的动力学稳定性,而结构-1动力学稳定性较差;3SiSHF在动力学上和热力学上都是最不稳定的结构.     

Harmonic operation of high gain harmonic generation free electron laser

In high gain harmonic generation (HGHG) free electron laser (FEL), with the right choice of parameters of the modulator undulator, the dispersive section and the seed laser, one may make the spatial bunching of the electron beam density distribution correspond to one of the harmonic frequencies of the radiator radiation, instead of the fundamental frequency of the radiator radiation in conventional HGHG, thus the radiator undulator is in harmonic operation (HO) mode. In this paper, we investigate HO of HGHG FEL.Theoretical analyses with universal method are derived and numerical simulations in ultraviolet and deep ultraviolet spectral regions are given. It shows that the power of the 3rd harmonic radiation in the HO of HGHG may be as high as 18.5% of the fundamental power level. Thus HO of HGHG FEL may obtain short wavelength by using lower beam energy.     

苯并氧化呋咱稳定性和异构化的DFT和ab initio研究

运用B3LYP/6-31G(d)密度泛函理论（DFT）方法对苯并氧化呋咱、邻二亚硝基苯及其间的异构化反应进行了计算研究。结果表明,苯并氧化呋咱的分子总能量比邻二亚硝基苯的低;由苯并氧化呋咱异构为邻二亚硝基苯的正向反应活化能（Ea+=51.0kJ/mol）,与文献实测值（58.6kJ/mol）较接近,而其逆向反应活化能（Ea-=4.6kJ/mol）很小,从而揭示了苯并氧化呋咱比邻二亚硝基苯更稳定·此外,进行了HF/3-21G、HF/6-31G(d)和MP2/6-31G(d)//6-31G(d)水平下相应的计算,发现B3LYP-DFT的结果较abinitio为优。谐振动频率的B3LYP/6-31G(d)计算还支持了邻二亚硝基苯为苯并氧化呋咱“自-自”互变重排反应的中间体。     

Synthesis of furan dimer‐based polyamides with a high melting point

Polyamide composed of furan dimer, which is prepared from biomass‐derived organic molecule 2‐furfural, is synthesized. The reaction of 2,2′‐furan dimer 5,5′‐dicarbonyl chloride with several 1,ω‐diamines was carried out with a solution or interfacial polycondensation leading to the corresponding polyamide. Measurement of the melting point was performed resulting to exhibit a higher temperature compared with the related polyamide bearing a single furan ring composed of furan‐2,5‐dicarboxylic acid (FDCA). Thermal analyses (TG–DTA) also indicated higher temperatures of decomposition than those of FDCA‐derived polyamide. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1516–1519