共查询到19条相似文献,搜索用时 185 毫秒
1.
利用SAC/SAC-CI方法,使用D95++、6-311++g及cc-PVTZ等基组,对BH分子的基态( X 1Σ+)、第一简并激发态( A 1Π)及第二激发态( B 1Σ+)的平衡结构和谐振频率进行了优化计算. 通过对三个基组计算结果的比较,得出了cc-PVTZ基组为三个基组中的最优基组的结论;使用cc-PVTZ基组,利用SAC的GSUM(group sum of operators)方法对基态( X 1Σ+), SAC-CI的GSUM方法对激发态( A 1Π 和 B 1Σ+)进行单点能扫描计算, 用正规方程组拟合Murrell-Sorbie函数,得到了相应电子态的完整势能函数;从得到的势能函数计算了与基态( X 1Σ+)、第一简并的激发态( A 1Π)和第二激发态( X 1Σ+)相对应的光谱常数(Be、αe、ωe 和ωeχe),结果与实验数据较为一致. 其中基态、第一激发态与实验数据吻合得较好. 相似文献
2.
采用内收缩MRCI方法(Internally Contracted Multiconfiguration-Reference Configuration Interaction)研究了OH自由基, 计算得到其基态稳定构型的键长是0.09708 nm, 对应的实验值是0.096966 nm, 第一激发态的键长是0.10137 nm,实验值是0.10121 nm. 同时得到势能曲线PECs (Potential Energy Curve), 再分别由Murrell-Sorbie势能函数拟合计算和POLFIT程序计算得到OH自由基在基态X 2Π和第一激发态A 2Σ +时的光谱数据:平衡振动频率 ωe, 非谐性常数 ωeχe以及高阶修正 ωeYe, 平衡转动常数 Be, 振转耦合系数 αe, 解离能 D0和垂直跃迁能量 ν00. 这些理论计算结果与最新的实验值非常吻合, 精确度比前人也有很大提高. 其中我们计算得到基态OH(X 2Π)的解离能 D0=35568.86 cm -1, 第一激发态OH (A 2Σ +)的解离能 D0=18953.93 cm -1, 从第一激发态A 2Σ + ( ν=0)到基态X 2Π ( v=0)的垂直跃迁能 ν00=32496.42 cm -1. 相似文献
3.
利用二维离子速度成像(Ion-Velocity Imaging)方法对二溴甲烷分子在234和267 nm附近的光解动力学行为进行了研究. 实验中得到了二溴甲烷光解产生的Br *( 2P1/2)和Br( 2P3/2)在不同波长下的角度和平动能分布. 在平动能分布中发现两个高斯分布, 推测其中主要是C—Br的快速解离, 而高能宽分布则来自于CH 2Br自由基的二次解离过程. 通过角度分布得到了Br *与Br中来自直接解离和非绝热交叉跃迁两种来源的比例. 结果表明Br *原子主要来自于B 1态的直接解离, 而Br则绝大部分是从B 1态向A 1的非绝热交叉跃迁得到, 并导致了两种解离通道能量分布的差别. 相似文献
4.
合成并表征了两个新的具有 “开放型蝶形” 结构的[2Fe2S]化合物 A和 B; 并以 A和 B为催化剂、 藻红B钠盐 (EBS 2-) 为光敏剂、 三乙胺 (TEA) 为电子给体和质子源, 构建了一个均相光催化产氢体系. 结果表明: 体系在pH为12, 体积比为1∶1的CH 3CN/H 2O溶液中,产氢活性最高,经4 h可见光照射,最大产氢量分别为156.1 μmol (37.9 TON vs. A) 和18.4 μmol (TON 4.6 vs. B); 催化剂中含有质子捕获位点, 有利于形成产氢活性中间体H 2-Fe 2S 2( η2-H 2-Fe IIFe I) 物种, 从而提高催化剂的产氢活性. 在当前的体系中, 还原态的 Fe IFe 0 物种通过 1* EBS 2-转移到Fe IFe I中心上, 然后再经历一个 EECC (化合物 A) 或 ECEC (化合物 B), 形成产氢活性中间体H 2-Fe 2S 2( η2-H 2-Fe IIFe I)物种, 最终产生H 2分子, 并使Fe IFe I 物种再生. 相似文献
5.
在超声分子束条件下,利用360.50 nm的电离激光使N 2O分子经由[3+1]共振增强多光子电离(REMPI)产生纯净的N 2O +(X 2Π(000))分子离子,用另一束解离激光在230-275 nm范围扫描获得N 2O +经由B 2П i←X 2Π跃迁产生的光解碎片(NO +和N 2+)激发(PHOFEX)谱. 获得的光解碎片激发谱可以归属为B 2П i(00n)←X 2Π(000)序列跃迁. 我们分别将线性三原子分子离子N 2O +中N―N伸缩振动简化成NO和N之间的简谐振动,N―O伸缩振动简化成N 2和O之间的简谐振动,用谐振子的简谐势能曲线和波函数对N 2O +分子离子X 2Π和B 2П i电子态振动能级间跃迁的Franck-Condon因子进行计算,和实验得到的碎片离子增强谱实验强度进行比较,对前人给出的分子数据(分子平衡核间距)进行验证,讨论了N 2O +经由B 2П i(00n)←X 2Π(000)电子态跃迁的光解离机理和碎片离子的分支比. 相似文献
6.
使用SAC/SAC-CI和D95++, 6-311++g, 6-311++g**及D95(d)基组, 分别对BF分子的基态X 1Σ +、第一简并激发态A 1Π和第二激发态B 1Σ +的平衡结构和谐振频率进行优化计算. 对所有计算结果进行比较, 得出6-311++g**基组为最优基组. 运用6-311++g**基组和SAC方法对基态X 1Σ +, SAC-CI方法对激发态A 1Π和B 1Σ +进行单点能扫描计算, 并用正规方程组拟合Murrell-Sorbie函数, 得到相应电子态的势能函数解析式, 由得到的势能函数计算了与X 1Σ +, A 1Π和B 1Σ +态相对应的光谱常数, 结果与实验数据较为一致. 相似文献
7.
在醇溶剂中合成了2个铜配合物[Cu(Ⅱ)(phen) 2Br] 2[Cu(Ⅰ) 4Br 6]( 1)和[Cu(Ⅱ)(phen) 2Br]Br·CH 3OH( 2)(phen=菲咯啉),并采用红外光谱、元素分析、热重和X射线单晶衍射对其进行了分析。 1是Cu(Ⅰ)-Cu(Ⅱ)混价态化合物,并通过 π- π作用和C-H…Br氢键作用形成了一个超分子网络结构。该化合物的结构单元包括2个[Cu(Ⅱ)(phen) 2Br] +阳离子和1个[Cu(Ⅰ) 4Br 6] 2-四核阴离子;阴离子中的4个铜原子组成四面体结构,而6个溴原子分别沿铜四面体的6个边桥联铜原子,形成八面体结构。 2由[Cu(Ⅱ)(phen) 2Br] +、Br -和CH 3OH组成,并通过 π- π作用也形成了一个超分子网络结构。当它们催化甲醇氧化羰基化合成碳酸二甲酯(DMC)时, 2仅显示了5.9的DMC转化数,而 1中的[Cu(Ⅰ) 4Br 6] 2-阴离子能为甲醇的氧化羰基化反应提供适宜的合成环境,DMC的转化数达到54.7。 相似文献
8.
用激光光解-激光诱导荧光方法研究了室温下( T=293 K) HCF( X~1A ’)自由基与SO 2分子的反应动力学. 实验中HCF( X~1A ’)自由基是由213 nm激光光解HCFBr 2产生的, 用激光诱导荧光(LIF)检测HCF( X~1A ’)自由基的相对浓度随着反应时间的变化, 得到此反应的二级反应速率常数为: k=(1.81±0.15)×10 -12 cm 38226;molecule -18226;s -1, 体系总压为1862 Pa. 高精度理论计算表明, HCF( X~1A ’)和SO 2分子反应的机理是典型的加成-消除反应. 我们运用RRKM-TST理论计算了此二级反应速率常数的温度效应和压力效应, 计算结果和室温下测定的二级反应速率常数符合得较好. 相似文献
9.
以原子为研究对象的原子连接性指数( mAt)被定义为: mAt=Σ( Ei× Ej× Ek×…) -0.5, E为价电子的能级值。其中: 0At=Σ( Ei) -0.5, 1At=Σ 相似文献
10.
以短链阳离子三聚表面活性剂C 10H 21N +(CH 3) 2(CH 2) 2N +(CH 3)(C 10H 21)(CH 2) 2N +(CH 3) 2C 10H 21]·3Br ?为结构导向剂, 通过2,7-二(3-三乙氧硅基氨丙酯基)萘(NIS)和四乙氧基硅烷(TEOS)共缩聚, 制备了有序的萘基桥联的杂化周期性介孔有机硅(PMOs). 样品通过X射线衍射(XRD)、高分辨透射电镜(HRTEM)、氮气吸附-脱附、差示扫描量热/热重分析(DSC/TGA)表征. 结果表明, 当NIS占NIS和TEOS总量40% (摩尔分数)时, 可以形成具有结晶态孔壁的有序介孔杂化材料. 当NIS含量低于或高于40%时, 分别形成无定形孔壁的有序介孔杂化材料和无孔杂化材料. 随着孔壁中萘基基团的增加, 由于有机基团之间π-π堆积作用增强, 杂化介孔材料显示良好的热稳定性. 由于在二氧化硅骨架中嵌入荧光萘基基团, 杂化有机-无机有序介孔材料显示了激基缔合物的光学行为. 随萘基基团含量的增加, 杂化材料的紫外吸收峰发生蓝移, 形成H聚集体; 由于聚集引起的荧光淬灭, 杂化材料的荧光量子产率明显降低. 相似文献
11.
在230nm激光激发下,氧硫化碳(OCS)分子迅速解离生成振动基态但高转动激发的CO(X~1∑_g~+,v=0,J=42-69)碎片,并通过共振增强多光子电离技术实现其离子化。通过检测处于J=56-69转动激发态CO碎片的离子速度聚焦影像,我们获得了各转动态CO碎片的速度分布和空间角度分布,其中包含了S(1D)+CO的单重态和S(~3P_J)+CO三重态解离通道的贡献。不同的转动态CO碎片对应三重态产物通道的量子产率略有不同,经加权平均我们得到230 nm附近光解OCS分子中S(3P)解离通道的量子产率为4.16%。结合高精度量化计算的OCS分子势能面和吸收截面的信息,我们获得了OCS光解的三重态解离机理,即基态OCS(X~1A')分子吸收一个光子激发到弯曲的A~1A'态之后,通过内转换跃迁回弯曲构型的基电子态,随后在C-S键断裂过程中与2~3A"(c~3A")态强烈耦合并沿后者势能面绝热解离。 相似文献
12.
Physico-chemical properties of the binary system NaHSO 4–KHSO 4 were studied by calorimetry and conductivity. The enthalpy of mixing has been measured at 505 K in the full composition range and the phase diagram calculated. The phase diagram has also been constructed from phase transition temperatures obtained by conductivity for 10 different compositions and by differential thermal analysis. The phase diagram is of the simple eutectic type, where the eutectic is found to have the composition X(KHSO 4) = 0.44 (melting point ≈ 406 K). The conductivities in the liquid region have been fitted to polynomials of the form κ( X) = A( X) + B( X)( T − Tm) + C( X)( T − Tm) 2, where Tm is the intermediate temperature of the measured temperature range and X, the mole fraction of KHSO 4. The possible role of this binary system as a catalyst solvent is also discussed. 相似文献
13.
The addition of electrons to form gas-phase multiply charged anions (MCAs) normally requires sophisticated experiments or calculations.In this work, the factors stabilizing the MCAs, the maximum electron uptake of gas-phase molecules, X, and the electronic stability of MCAs X Q-, are discussed. The drawbacks encountered when applying computational and/or conceptual density functional theory (DFT) to MCAs are highlighted. We develop and test a different model based on the valence-state concept. As in DFT, the electronic energy, E( N, vex), is a continuous function of the average electron number, N, and the external potential, vex, of the nuclei. The valence-state-parabola is a second-order polynomial that allows extending E( N, vex) to dianions and higher MCAs. The model expresses the maximum electron acceptance, Qmax, and the higher electron affinities, AQ, as simple functions of the first electron affinity, A1, and the ionization energy, I, of the "ancestor" system. Thus, the maximum electron acceptance is Qmax, calc = 1 + 12 A1/7( I -A1). The ground-state parabola model of the conceptual DFT yields approximately half of this value, and it is termed Qmax, GS = ${}^{1}\!\!\diagup\!\!{}_{2}\; $ + A1/( I -A1). A large variety of molecules are evaluated including fullerenes, metal clusters, super-pnictogens, super-halogens (OF 3), super-alkali species (OLi 3), and neutral or charged transition-metal complexes, AB mL n0/+/-. The calculated second electron affinity A2, calc = A1-(7/12)( I -A1) is linearly correlated to the literature references A2, lit with a correlation coefficient R = 0.998. A2 or A3 values are predicted for further 24 species. The appearance sizes, nap3-, of triply charged anionic clusters and fullerenes are calculated in agreement with the literature. 相似文献
14.
通过193 nm光解丁烯酮分子产生乙烯基自由基(C 2H 3). 经射流冷却后, 用另一束激光光解C 2H 3, 生成的氢原子碎片经共振增强多光子电离(REMPI)过程, 记录氢离子信号随光解波长变化, 得到20020~20070 cm -1范围内乙烯基激发的转动分辨光谱. 该谱对应于 A2A'(v'=0)← X2A'(v'=0)跃迁的转动结构. 结合量子化学理论计算、光谱拟合以及前人的研究结果, 对该段光谱进行了完整的转动识别, 确定了40条转动谱线的位置. 由光谱拟合还得到 A2A'(v'= 0 )能级的预解离寿命为3.3 ps, 且不依赖于转动量子数. 相似文献
15.
The effect of treatment at pH = 11 on the photosystem II was studied by EPR and electron spin echo envelope modulation (ESEEM). The magnetic interaction between the semiquinone Q A−. and the non-heme Fe 2+ ( S = 2) was absent. ESEEM showed that the Q A−. interacts magnetically with two 14N nuclei. The first interaction has a hyperfine coupling tensor ( AXX, AYY, AZZ)=(2.0, 1.7, 2.3 MHz) and nuclear quadrupole interaction parameters e2qQ/ h=3.24 MHz and η = 0.45 while those of the second are ( AXX, AYY, AZZ)=(1.2, 1.5, 2.3 MHz), e2qQ/ h = 1.56 MHz and η = 0.71. These are assigned to an amide nitrogen of the peptide backbone and the amino nitrogen of an imidazole respectively. By analogy to the bacterial reaction centre, these nitrogens are attributed to the Ala 261 and His 215 of the D2 protein. It was shown earlier that the imidazole coupling is absent in cyanide-treated PSII, its presence here is attributed to a difference in the position of the imidazole group itself. 相似文献
16.
The dinuclear cyclopalladated complexes [Pd(L 1 or L 2)(µ- X)] 2 (HL 1=5-alkyl-2-(4'-alkoxyphenyl)pyrimidine, HL 2=3-(4'-alkoxyphenyl)-6-alkoxypyridazine, X=Cl -, CH 2ClCOO -, CH 2BrCOO -, CH 3CHBrCOO -, CH 2BrCH 2COO -, CH 3COO -) have been synthesized and characterized; their mesogenic properities were determined by DSC and polarizing microscopy. The effect of the bulk and the polarity of the bridging ligands on their mesogenic properties is discussed. The effect of the length of the alkyl chains on the mesogenic properties of these organometallic complexes has also been investigated. 相似文献
17.
The monolayer behavior of three mixed systems of dipalmitoyl phosphatidyl choline (DPPC) with sterols; cholesterol (Ch), stigmasterol (Stig), and cholestanol (Chsta) formed at the interface of air/water (phosphate buffer solution at 7.4 with addition of NaCl) was investigated in terms of surface pressure ( π) and molecular occupation surface area ( A) relation. A series of π– A curves at every 0.1 mol fraction of each sterol for the three combinations of mixed systems were obtained at 25.0 °C. On the basis of the π–A curves, the additivity rule in regard to A versus sterol mole fraction (Xst) was examined at discrete surface pressures such as 5, 10, 15, 20, 25, 30 mN m−1, and then from the obtained A–Xst curves the partial molecular areas (PMA) were determined. The A–Xst relation exhibited a marked negative deviation from ideal mixing in the pressure range below 10 mN m−1, i.e. in the expanded liquid film region (below the transition pressure of DPPC). The PMA of Ch at π=5 mN m−1, for example, was found to be conspicuously negative in the range of XCh=0–0.2 (about −0.4 nm2 per molecule) and slightly positive (ca. 0.1 nm2 per molecule) in the range XCh=0.2 to 0.4. Above XCh=0.5, Ch’s PMA was almost the same as the surface area of pure Ch, while DPPC’s PMA was reduced to 60% of that of the pure system. Excess Gibbs energy (ΔG(ex)) as a function of Xst was estimated at different pressures. Applying the regular solution theory to thermodynamic analysis of ΔG(ex), the activity coefficients (f1 and f2) of DPPC and the respective sterols as well as the interaction parameter (Ip) in the mixed film phase were evaluated; the results showed a marked dependence on Xst. Compressibility Cs and elasticity Cs−1 were also examined. These physical parameters directly reflected the mechanical strength of formed monolayer film. Phase diagrams plotting the collapse pressure (πc) against Xst were constructed, and the πc versus Xst curves were examined for the respective mixed systems in comparison with the simulated curves of ideal mixing based on the Joos equation. Comparing the monolayer behavior of the three mixed systems, little remarkable difference was found in regard to various aspects. In common among the three combinations, the mole fraction dependence in monolayer properties was classified into three ranges: 0<Xst<0.2, 0.2<Xst<0.4 and 0.5<Xst<1. How the difference in the chemical structure of the sterols influenced the properties was examined in detail. 相似文献
18.
用密度泛函UB3LYP/6-311++G(3 df, 3 pdpd)//6-311G(2 dd, p)方法计算研究了在二重态和四重态两个势能面上的气相反应:CrO 2+ + H 2→CrO ++ H 2O. 对影响反应机理和反应速率的势能面交叉进行了讨论, 并运用Hammond 假设和Yoshizawa 等的内禀反应坐标(IRC)单点垂直激发计算的方法找出了势能面交叉点(crossing point (CP)). 运用碎片分子轨道(fragment molecular orbital(FMO))理论, 对初始复合物2IM1和4IM1的轨道相关进行了分析, 解释了CrO 2+活化H—H σ键及H 2迁移的机理. 相似文献
19.
用中和法合成了氨基酸离子液体1-乙基-3-甲基咪唑丙氨酸([C 2mim][Ala]),并利用恒温环境的溶解反应热量计,在(288.15±0.01) K-(308.15±0.01) K温度范围内每隔5 K,测定不同质量摩尔浓度离子液体在水中的溶解焓(Δ solHmθ).根据Archer的方法,通过线性拟合得到了该离子液体的标准摩尔溶解焓(Δ sol),并计算了其相对表观摩尔溶解焓( ΦL).在298.15 K下,根据Glasser经验方法得到了格子能 UPOT = 566 kJ·mol -1,并计算了其阴阳离子水化焓值(Δ H+ + Δ H-) = -620 kJ·mol -1及阴离子水化焓Δ H-([Ala] -) = -387 kJ·mol -1.此外,估算了[C 2mim][Ala]水溶液的热容( Cp(sol))和表观摩尔热容( ΦCp). 相似文献
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