Spectroscopic characterization and theoretical simulation of 1,4-diallylquinoxaline-2,3-dione self dimer

Room temperature UV-vis absorption and emission spectra of the 1,4-diallylquinoxaline-2,3-dione (DAQX) are measured in solution at different concentrations. Even at very low concentration (approximately 10(-7)M), DAQX is shown to form ground state van der Waals dimers and excited dimers. These later species do not seem to rearrange into an excimer geometry. The theoretical simulation of the dimer, performed using the analytical atom-atom pair potential described below, predicts a non sandwich face-to-reverse slipped structure with head-to-tail orientation. The allowed absorption transitions, calculated using ZINDO/S package, reproduce satisfactory the experimental spectrum for both the monomer and the simulated dimer.     

All electron ab initio investigations of the electronic states of the FeC molecule

The low-lying electronic states of the molecule FeC have been investigated by performing all electron ab initio multi-configuration self-consistent-field (CASSCF) and multi reference configuration interaction (MRCI) calculations. The relativistic corrections for the one-electron Darwin contact term and the relativistic mass-velocity correction have been determined in perturbation calculations. The electronic structure of the FeC molecule is interpreted as antiferromagnetic couplings of the localized angular momenta of the ions and resulting in a triple bond in the valence bond sense. The electronic ground state is confirmed as being . The spectroscopic constants for the ground state and eleven excited states have been derived from the results of the MRCI calculations. The spectroscopic constants for the ground state have been determined as and ,and for the low-lying state as and . The values for the ground state agree well with the available experimental data. The FeC molecule is polar with charge transfer from Fe to C. The dipole moment has been determined as in the ground state and as 1.51 D in the state. From the results of the MRCI calculations the dissociation energy, , is determined as 2.79 eV, and D₀ as 2.74 eV. Received: 2 October 1998 / Received in final form: 30 March 1999     

How to get access to long range states of highly excited molecules

Due to competition between ionic and covalent dissociation, the excited potential curves of the alkali dimers display long range structures, leading in some cases to secondary wells. We discuss the possibility of populating the well (with a depth of 1614.8 cm^-1, located at R _e = 30.5a ₀ ) that is present in the Na₂ potential curve and propose detection schemes. Received: 28 May 1998 / Revised: 5 August 1998 / Accepted: 24 September 1998     

Kinetic investigation of electronic energy transfer processes following the pulsed dye-laser generation of excited atomic barium, Ba[6s6p(P1)], in the presence of atomic strontium

The collisional behaviour of Ba[6s5d(³D_J)], 1.151 eV above the 6s²(¹S₀) electronic ground state, in the presence of atomic strontium, has been investigated in the ‘long-time domain' (ca. 100 μs–1 ms) following the pulsed dye-laser excitation of barium vapour at elevated temperature at λ = 553.5 nm (Ba[6s6p(¹P₁)] ← Ba[6s²(¹S₀)]. Ba(³D_J) is subsequently produced from the short-lived ¹P₁ state (τ_e = 8.37 ± 0.38 ns) by a number of radiative and collisional processes. It may then be monitored in the ‘long-time domain' by atomic spectroscopic marker methods involving either collisional activation of Ba(³D_J) by Ba(¹S₀) and He buffer gas to yield Ba[6s6p(³P_J)] with subsequent emission from the ³P₁ state (τ_e = 1.2 ± 0.1 μs): Ba[6s6p(³P₁)] → Ba[6s²(¹S₀)] + hv (λ = 791.1 nm). Alternatively, emission from Ba(¹P₁) may be monitored at long times following the generation of this short-lived state by energy pooling following self-annihilation of Ba(³D_J) + Ba(³D_J) from Ba[6s6p(¹P₁)] → Ba[6s²(¹S₀)] + hv (λ = 553.5 nm). The generation of Ba(³D_J) in the presence of atomic strontium yields emission in the long-time domain from Sr[5s5p(³P₁)] (τ_e = 19.6 μs): Sr[5s5p(³P₁)] → Sr[5s²(¹S₀)]  + hv (λ = 689.3 nm). Whilst the decay profiles at short times are complex in form, at long times all these atomic profiles show first-order kinetic removal with the decay coefficients for λ = 791.1 nm, 689.3 nm and 553.5 nm emissions in the ratio 1 : 2 : 2, consistent with overall third-order activation of the form: Ba(³D_J) + Ba(³D_J) + Sr(¹S₀) → Sr(³P_J) + 2Ba(¹S₀). The mechanism is modelled in detail, including measurement of integrated emission intensities, yielding kinetic data for fundamental collisional processes. The overall rate constant for the third-order collisional activation of Sr[5s5p(³P_J])from 2Ba[6s5d(³D_J)] + Sr[5s²(¹S₀)] takes the upper limit of 5.8 × 10⁻²⁷ cm⁶ atom⁻² s⁻¹ (T = 900 K). The rate constant for the two body collisional quenching of Ba[6s5d(³D_J)] by ground state atomic strontium, Sr[5s²(¹S₀)], is found to be (2.0 ± 0.1) × 10⁻¹² cm³ atom⁻¹ s⁻¹ (T = 900 K).     

波长40—60nm的高电离态硫离子某些能级跃迁谱线的实验研究

波长４０－６０ｎｍ的元素高电离态离子光谱实验中,观测到１０多条光谱线,这些谱线是ＳＸＩ到ＳＸⅣ离子的一些激发能级发射的,其中９条谱线还没有人报道实验结果,实验分析结果与理论符合得较好。     

高聚物介质中7-羟基喹啉的光谱特性

通过观测７－羟基喹啉（７ＨＱ）在甲基丙烯酸甲酯（ＭＭＡ）和甲基丙烯酸（ＭＡＡ）以不同配比共聚的基质中的吸收光谱和荧光光谱,研究基质对７ＨＱ各物种相对含量的变化和对７ＨＱ激发态质子转移的影响。结果表明基质中羧基数目增加,可使７ＨＱ各物种的相对含量发生变化,并有利于７ＨＱ发生激发态质子转移。     

塞来昔布的密度泛函理论计算及光谱分析

塞来昔布(Celecoxib, CXB)是COX-2的高选择性抑制剂,经过20年的发展已经成为世界范围内使用最为广泛的一类处方药.本文基于密度泛函理论,使用B3LYP泛函,6-311++G(d, p)基组进行结构优化.在此工作上对该药物分子的结构、红外光谱、拉曼光谱、分子前线轨道、静电势和激发态性质做了一系列的研究.结果表明：CXB分子是一个稳定的非平面扭曲结构,此结构使得该药物分子在COX-2上的疏水通道中可以迅速通过,从而形成了一个可与苯磺酰胺片段结合的结合腔.对化合物进行频率计算,分别得到红外光谱和拉曼光谱,与实验采集的数据进行对比,呈现出较好的一致性.对分子的基态进行前线轨道和静电势的分析,磺酰胺基与COX-2易形成氢键作用.在CXB分子的激发态研究中发现,CXB分子的激发态性质主要由第1激发态、第3激发态和第6激发态共同决定.这为理解CXB的作用机理提供了重要的信息,也为后期扩展CXB衍生物提供了理论基础.     

Effect of energy dependent cross-section on flow velocity measurements with charge exchange spectroscopy in magnetized plasma

Charge exchange spectroscopy (CXS) is widely used to measure plasma flow velocity. Accurate measurement is heavily affected by energy dependent cross section between neutral atoms and impurity ions. One symmetric layout of poloidal CXS is applied on Large Helical Device. Correction velocity due to the cross section is exacted from total velocity when actual plasma flow velocity is acquired with the benefit of this layout. A linear relationship between correction velocity and ion temperature is observed. Abundant discharges with wide plasma conditions are investigated and the ratio of correction velocity to ion temperature with the same beam energy shows the normal distribution. The impact of beam energy on the ratio of correction velocity to ion temperature of the carbon system and the hydrogen system is discovered based upon the statistics. Effective emission coefficient (Q) from Atomic Data and Analysis Structure (ADAS) is utilized to study the dependence of correction velocity on Q. The relationship in which the ratio of correction velocity to ion temperature increases linearly with the increasing normalized effective emission coefficient ((1/Q)dQ/dv) is observed. Experimental (1/Q)dQ/dv is obtained according to this observation, and comparison with different fractions of n?=?2 excited state is also discussed. The influence of different receivers (carbon and hydrogen) is also presented. The experimental (1/Q)dQ/dv from the carbon system decreases with beam energy decreasing when beam energy is less than 30 keV/amu. This tendency of (1/Q)dQ/dv at low beam energy indicates the existence of the contribution of n?=?2 excited state donors to the cross section.     

N,N'-二-[3-羟基-4-(2-苯并噻唑)苯基]脲的光谱实验与密度泛函理论研究

利用实验观测与密度泛函理论(DFT)计算方法考察了新化合物N, N'-二-[3-羟基-4-(2-苯并噻唑)苯基]脲(4-DHBTU)的红外、核磁与紫外吸收光谱性质.与单体2-(4-氨基-2-羟苯基)苯并噻唑(4-AHBT)相比, 4-DHBTU的实验紫外吸收强度显著增强,最大吸收峰发生了明显红移,并呈现出双吸收峰特征.结合实验光谱数据与密度泛函理论计算分析表明, 4-DHBTU分子最稳定的基态异构体为cis-C₁₁和trans-C₁₁,而导致上述紫外光谱差异的主要原因是4-DHBTU样品中cis-C₁₁, trans-C₁₁, cis-C₂₂, trans-C₂₂等多种异构体共存.此外, 4-DHBTU与溶剂二甲基亚砜(DMSO)间氢键作用使得核磁实验中4-DHBTU的15H、16H氢谱化学位移显著增大.     

Partial wave analysis of J/ψ→pp(-)π~0 and measurement of J/ψ→pp(-)η, pp(-)η'

Based on 58 million J/ψ data collected with the BES Ⅱ detector at the BEPC, Partial Wave Analysis(PWA) is performed on J/ψ→pp(-)π~0. The new excited baryon N(2065) is confirmed. Clear signals for other N~* states are observed and the corresponding masses, widths and spin-parity are also measured. Processes such as J/ψ→pp(-)η,pp(-)η' are also studied and the branching ratios are measured.