二硫化碳气体近紫外吸收截面积测定

利用二极管阵列光谱仪,室温条什下,在波长220～380 nm的波段内,测量了CS2的紫外吸收截面积.发现CS2在315 nm处具有较大吸收,其值为σ=7.184×1020cm2·molecule-1.与文献报道进行了比对,吻合较好,并利用所获得的数据对CS2大气光解寿命进行了评估.     

热氢原子碰撞导致的CO2(v3)的高振动激发

用时间分辨-傅里叶变换红外发射光谱研究了热的氢原子与CO2分子间高效率的平动-振动(T-V)能传递.热的氢原子由ArF激光光解H2S得到,这种氢原子的平动能为223 kJ/mol.实验中观察到了从2130 cm-1到2400 cm-1的红外发射谱带,它归属于高振动激发的CO2分子的非对称伸缩振动(v3).对这一发射谱带的光谱拟合显示CO2的非对称伸缩振动被激发到了较高的振动态,振动量子数达到了v=7.并且有5580 cm-1的能量经传能过程由氢原子到达了CO2的v3模.实验条件下氢原子与CO2的T-V传能效率为0.30.实验结果与Schatz等人的用3D半经典计算预测的碰撞截面符合的很好.     

Mechanistic Studies on the Photogenerated Dienol with α-Phenyl-N-tert-Butylnitrones

The mechanism for the photochemical reactions of o-methyl-benzaldehyde ( 1 ), o-methyl-acetophenone ( 2 ) and o-methyl-benzophenone ( 3 ) in the presence of α-phenyl-N-tert-butylnitrone (PBN) to the formation of stable nitroxyl radicals 4–6 is studied. The nitroxyl radical product 6 can also be obtained by the thermolysis of benzocyclobutenol with PBN. Thus, the radical products were derived from a novel and regioselective 4+2 cycloaddition of the photogenerated dienol intermediate with PBN.     

铁－芳烃络合物光引发剂的吸收光谱研究

铁－芳烃络合物光引发剂的吸收光谱研究陈旭东，黄新华陈用烈，梁兆熙（西南师范大学化学系重庆，６３０７１５）（中山大学高分子研究所广州）关键词铁－芳烃络合物，光引发剂，吸收光谱，光解铁－芳烃络合物作为环氧化物阳离子聚合光引发剂已引起人们关注［１，２］．我...     

Studying the photochemical fate of methyl parathion in natural waters under tropical conditions

This article discusses the degradation of methyl parathion (MP) in natural and sterilized waters. Experiments were prepared using natural waters gathered in two aquatic systems (Rio de Janeiro State, Brazil), ultra-pure water and humic water solution under different conditions (i.e. in the presence/absence of light, sterilized/no sterilize solutions). The exposition to sunlight was carried out using experimental bottles without headspace immersed in a swimming pool for temperature control. Natural waters results showed that the degradation kinetic of MP is of first order and the half-lives for lake water experiments, under direct sunlight and shade, were 4.41 and 6.89 days, respectively. The kinetic curve for MP degradation in river waters showed that there are no differences when samples were sterilized and placed (or not) under shade conditions, and the half-lives ranged from 5.37 to 2.75 days for sterilized river water/absence of sunlight and natural/presence of sunlight, respectively. Therefore, our results showed that photolysis plays, in addition to bio- and chemical degradation, an important role in the decomposition of MP in aquatic environments.     

Photolysis of H_2S with interior microwave discharge electrodeless lamps

<正>The luminescent properties of microwave discharge electrodeless mercury lamp(MDEL-Hg) which was ignited within the resonant cavity and photolysis of hydrogen sulfide with low concentration were studied in this paper.Experiment results indicated that the Interior MDEL-Hg could be made the best of energy utihzation and the efficiency of photolysis of H_2S was very significant under the experimental conditions with the initial H_2S concentration of 7.9 mg m~(-1).With residence time of 1.5 s,the removal efficiency of hydrogen sulfide was 91%,the absolute removal amount(ARA) was 3.24μg s~(-1) and the energy consumption was 58.23 mg(kWh)~(-1).     

Photolysis rate coefficients in the upper atmosphere: Effect of line by line calculations of the O2 absorption cross section in the Schumann-Runge bands

A line by line (LBL) method to calculate highly resolved O₂ absorption cross sections in the Schumann-Runge (SR) bands region was developed and integrated in the widely used Tropospheric Ultraviolet Visible (TUV) model to calculate accurate photolysis rate coefficients (J values) in the upper atmosphere at both small and large solar zenith angles (SZA). In order to obtain the O₂ cross section between 49,000 and 57,000 cm⁻¹, an algorithm which considers the position, strength, and half width of each spectral line was used. Every transition was calculated by using the HIgh-resolution TRANsmission molecular absorption database (HITRAN) and a Voigt profile. The temperature dependence of both the strength and the half widths was considered within the range of temperatures characteristic of the US standard atmosphere, although the results show a very good agreement also at 79 K. The cross section calculation was carried out on a 0.5 cm⁻¹ grid and the contributions from all the lines lying at ±500 cm⁻¹ were considered for every wavelength. Both the SR and the Herzberg continuums were included. By coupling the LBL method to the TUV model, full radiative transfer calculations that compute J values including Rayleigh scattering at high altitudes and large SZA can now be done. Thus, the J values calculations were performed for altitudes from 0 to 120 km and for SZA up to 89°. The results show, in the J_O2 case, differences of more than ±10% (e.g. at 96 km and 30°) when compared against the last version of the TUV model (4.4), which uses the Koppers and Murtagh parameterization for the O₂ cross section. Consequently, the J values of species with cross sections overlapping the SR band region show variable differences at lower altitudes. Although many species have been analyzed, the results for only four of them (O₂, N₂O, HNO₃, CFC12) are presented. Due to the fact that the HNO₃ absorption cross section extends up to 350 nm this molecule was used to verify the consistency of the new TUV-LBL at lower altitudes. Thus, it shows differences up to 5.7% at 21 km but 0% in the troposphere. Because of the more accurate consideration of the Rayleigh scattering the distribution of the actinic flux in its direct and diffuse components (in the SR bands wavelength interval) is also modified.     

Micelle formation induced by photolysis of a poly(<Emphasis Type="Italic">tert</Emphasis>-butoxystyrene)-<Emphasis Type="Italic">block</Emphasis>-polystyrene diblock copolymer

We found the novel photolysis-induced micellization of the poly(tert-butoxystyrene)-block-polystyrene diblock copolymer (PBSt-b-PSt). PBSt-b-PSt with a molecular weight of Mn(PBSt-b-PSt) = 15,000-b-97,000 showed no self-assembly in dichloromethane and existed as isolated copolymers with a hydrodynamic diameter of 16.6 nm. Dynamic light scattering demonstrated that the copolymer produced micelles with a 63.0 nm hydrodynamic diameter when the copolymer solution was irradiated with a high-pressure mercury lamp at room temperature in the presence of bis(alkylphenyl) iodonium hexafluorophosphate, a photoacid generator. The ¹H NMR analysis revealed that the micellization resulted from the photolysis of the PBSt blocks into insoluble poly(vinyl phenol) blocks based on the fact that the signal intensity of the tert-butyl protons decreased over time during the irradiation. It was found that the micellization rapidly proceeded as the degree of the photolysis reached over 50% and was completed at 90%.     

Synthesis of pyrrolo[2,3-d]pyrimidine-2,4-diones by sunlight photolysis of N-(5-vinyluracil-6-yl)sulfilimines

Uracil derivatives having a vinyl group at the C-5 position and a sulfilimine moiety at the C-6 position were prepared and cyclized to 1,3,6-trisubstituted pyrrolo[2,3-d]pyrimidine-2,4-diones by sunlight photolysis in good yields.     

Photoinstability in active pharmaceutical ingredients: Crystal engineering as a mitigating measure

Cocrystallization has evolved as an attractive prospect to broaden the chemical landscape of a drug entity, expand its therapeutic scope, and address physicochemical deficiencies of an active pharmaceutical ingredient (API). The non-covalent approaches to address the solubility and bioavailability of BCS Class-II and Class-IV drugs is an archetypal example and is a prolific topic. The present review highlights various supramolecular methods employed in addressing the photoinstability in drugs, emphasizing crystal engineering approaches. Because a greater proportion of the drugs are formulated in the solid-state, the structural factors—crystal packing, intermolecular interactions, packing density—remain a critical determinant in the observed extent of stability. Comprehending and amending these structural determinants using crystal engineering concepts proposes to address the photoinstability in drugs. Also, we highlight the pros and cons of the different adopted strategies in terms of formulation and the underlying challenges and put in prospect. The review provides a correlative assessment of the structure-property relations that could further augment the foundations of factual knowledge in drug stability.