Photoacoustic Spectrometry Investigation and Determination of Rare Earth Ions Ho3+ and Nd3+ in a Solution

A home-made high sensitive photoacoustic transducer was used to determine the photoacoustic signal in a solution. The photoacoustic spectra of Ho in different solvents were measured and comparedwith its absorption spectrum. The affection factors of photoacousticsensitivity are discussed. The trivalent rare earth ions Ho3+ and Nd3+in an aqueous acetonitrile solution were determined. The detection limit is 5×10-8 mol/L for Ho3+ and 1.0 ×10-7 mol/L for Nd3+, and corresponds to the absorbance of 1.5×10 and 6.3×10-7.respectively.     

The predissociation of Li2 b3Πu by a3Σ+u

⁶Li₂ 1³Δ_g(F₁) → b³Π_u(F₁v = 0–11) rotationally resolved fluorescence spectra are recorded following perturbation-facilitated optical—optical double resonance excitation of 1³Δ_g via spin—orbit mixed A¹Σ⁺_u ∼ b³Π_u(F₁e) intermediate levels. The f-symmetry Λ-components of b³Π_u(F₁) are broadened above the 0.05 cm⁻¹ detection threshold owing to predissociation by the vibrational continuum of the a³Σ⁺_u state. The observed v = 0–11, N = 31f level widths were used to determine the potential energy curve for the Li₂ a³Σ⁺_u state in the region 2.35 < R < 2.60 Å and 11200 < E < 14900 cm⁻¹ (relative to E = 0 at the minimum of X¹Σ⁺_g). The a³Σ⁺_u ∼ b³Π_u curve crossing is at R = 2.57 Å and E = 11246 cm⁻¹ and the electronic part of the − BN·LL-uncoupling matrix element is 〈b Π¦L⁺ ¦aΣ〉 = 1.216H at an R-centroid Rv_bϵ_a = 2.61Å.     

Ga3+对Ce3+光致发光的影响

研究了Ｇａ３＋在ＳｒＳ∶Ｃｅ和ＳｒＧａ２Ｓ４∶Ｃｅ薄膜电致发光（ＴＦＥＬ）材料中的作用及其对Ｃｅ３＋发光特性的影响。在ＳｒＳ中掺入Ｇａ２Ｓ３并烧结，发现Ｇａ３＋的浓度增加时，Ｃｅ３＋的发光显著向短波方向移动，激发谱中对应于ＳｒＳ带间吸收的激发峰相对减弱，而对应于Ｃｅ３＋的基态到激发态跃迁的激发效率相对提高，并出现逐渐增强的ＳｒＧａ２Ｓ４的带间吸收。Ｇａ３＋的引入使Ｃｅ３＋周围的配位场发生变化，相应的能级分布有所改变，Ｓｒ２＋离子性的增强和Ｃｅ３＋－Ｃｅ３＋相互作用的减弱对Ｃｅ３＋发光特性有显著影响。     

Crystallographic study of YCo3+1−2xCo2+xPt4+xO3 and DyCo3+1−2xCo2+xPt4+xO3

The crystal structures of single crystals of YCo³⁺_.36Co²⁺_.32Pt⁴⁺_.32O₃ and DyCo³⁺_.36Co²⁺_.32Pt⁴⁺_.32O₃ have been examined at room temperature, and shown to be isostructural with GdFeO₃, which belongs to space group Pbnm. The overall expansion of octahedra caused by substitution of platinum enhances the distortion of rare-earth dodecahedra by moving 4 out of 12 oxygens further away from the rare-earth ions, as shown by the rotation of octahedra along the [110] axis. No order has been found for Co²⁺, Co³⁺, and Pt⁴⁺.     

CF3CH3 --> HF + CF2CH2: a non-RRKM reaction?

The experimental shock tube data recently reported by Kiefer et al. [J. Phys. Chem. A 2004, 108, 2443-2450] for the title reaction at temperatures between 1600 and 2400 K have been compared to master equation simulations using three models: (a) standard RRKM theory, (b) RRKM theory modified by local random matrix theory, which introduces dynamical corrections arising from slow intramolecular vibrational energy randomization, and (c) an ad hoc empirical non-RRKM model. Only the third model provides a good fit of the Kiefer et al. unimolecular reaction rate data. In separate simulations, all three models accurately reproduce the experimental 300 K chemical activation data of Marcoux and Setser [J. Phys. Chem. 1978, 82, 97-108] when the energy transfer parameters are freely varied to fit the data. When experimental energy transfer parameters for a geometrical isomer (1,1,2-trifluoroethane) are used, the standard RRKM model fits the chemical activation data better than the other models, but if energy transfer in the 1,1,1-trifluoroethane is significantly reduced in comparison to the 1,1,2 isomer, then the empirical ad hoc non-RRKM model also gives a good fit. While the ad hoc empirical non-RRKM model can be made to fit the data, it is not based on theory, and we argue that it is physically unrealistic. We also show that the master equation simulations can mimic the Kiefer et al. vibrational relaxation data, which was the first shock tube observation of double-exponential relaxation. We conclude that, until more data on the trifluoroethanes become available, the current evidence is insufficient to decide with confidence whether non-RRKM effects are important in this reaction, or whether the Kiefer et al. data can be explained in some other way.     

Fourier spectrometry investigation of the 1 3Σg+ →a 3Σu+ transition of the 7Li2 molecule

The 1 ³Σ_g⁺ → a ³Σ_u⁺ transition in the ⁷Li₂ molecule has been observed in the 8200–10 000 cm⁻¹ region with a high resolution Fourier spectrometer. Rotational analysis of 1 ⩽ υ′ ⩽ 7 of 1 ³Σ_g⁺ and 0 ⩽ υ″ ⩽ 7 of a ³Σ_u⁺ has been carried out. We found D_e(a ³Σ_u⁺) = 332.5 ± 1.0 cm⁻¹ that gives T_e(a ³Σ_u⁺) = 8184.3 ± 1.5 cm⁻¹ and D_e(1 ³Σ_g⁺) = 7090.4 ± 1.5 cm⁻¹ with T_e = 16330 ± 2 cm⁻¹.     

Mechanisms of the reactions of propane with CBr3+ cation and superelectrophilic complex CBr4+·AlBr3- containing a bromine-centered cationic center: a theoretical study

Fragments of the potential energy surfaces (PES) of the systems [C₃H₈ + CBr₃ ⁺] and [C₃H₈ + Br₂CBr⁺·Br₂AlBr₂ ^–] were simulated by the MNDO/PM3 method. Energy minima corresponding to weakly bound adducts of propane molecule with the CBr₃ ⁺ cation or neutral complex CBr₃ ⁺·AlBr₄ ^– were found on the PES's of both systems. These are adducts with the coordination of a H atom of the methylene group of the propane molecule to the electrophile at the Br atom carrying the largest positive charge. As the fragments of the adducts are brought close together, the coordinated H atom migrates to the C atom of the CBr₃ ⁺ fragment. The potential barriers of these migrations were found to be low for both systems. The reactions proceed without formation of cyclic intermediates or transition states typical of the Olah mechanism.     

From a localized H3O radical to a delocalized H3O+···e- solvent-separated pair by sequential hydration

The impact of microhydration on the electronic structure and reactivity of the H(3)O moiety is investigated by ab initio calculations. In the gas phase, H(3)O is a radical with spin density localized on its hydrogen end, which is only kinetically stable and readily decomposes into a water molecule and a hydrogen atom. When solvated by a single water molecule, H(3)O preserves to a large extent its radical character, however, two water molecules are already capable to shift most of the spin density to the solvent. With three solvating water molecules this shift is practically completed and the system is best described as a solvent-separated pair of a hydronium cation and a hydrated electron. The electronic structure of this system and its proton transfer reactivity leading to formation of a hydrogen atom already resemble those of a proton-electron pair in bulk water.     

Structural and spectral consequences of ion pairing II. a theoretical study of CIO−3Li+ and ClO−3Na+

The structure of ClO⁻₃M⁺ ion pairs (M = Li, Na) has been examined with the aid of ab initio molecular orbital calculations. The calculations support recent experimental findings that ClO⁻₃ M ion paris have C_3v rather than C_s configurations. Results from these studies also show that the metal cation prefers to coordinate at the base of the chlorate anion pyramidal structure along the C₃ axis. Calculated vibrational frequencies, intensities, isotopic frequency shifts, and isotopic substituted frequency and intensity patterns render support to this conclusion. New vibrational assignments of observed and some unassignable bands from previous matrix-isolation and molten gas phase spectroscopic studies of ClO⁻₃M⁺ ion pairs are provided.     

BaGdB~9O~16中Dy^3+的发光和Ce^3+, Gd^3+驿Dy^3+的能量传递

我们研究了在紫外光(UV)激发下, Dy^3+单掺杂和Ce^3+, Dy^3+共掺杂的BaGdB~9O~16的发射光谱、激发光谱及发光强度随组成变化的规律性, 发现Ce^3+,Gd^3+均对Dy^3+的发光起敏化作用。Ce^3+吸收的能量大部分直接传递给Dy^3+, 小部分以Ce^3+→Gd^3+→(Gd^3+)~n→Dy^3+形式传递给Dy^3+。Ce^3+→Dy^3+能量传递和Dy^3+自身浓度猝灭机理分别为电偶极-电偶极和电偶极-电四级相互作用。     

BaGdB~9O~16中Dy^3+的发光和Ce^3+, Gd^3+驿Dy^3+的能量传递

我们研究了在紫外光(UV)激发下, Dy^3+单掺杂和Ce^3+, Dy^3+共掺杂的BaGdB~9O~16的发射光谱、激发光谱及发光强度随组成变化的规律性, 发现Ce^3+,Gd^3+均对Dy^3+的发光起敏化作用。Ce^3+吸收的能量大部分直接传递给Dy^3+, 小部分以Ce^3+→Gd^3+→(Gd^3+)~n→Dy^3+形式传递给Dy^3+。Ce^3+→Dy^3+能量传递和Dy^3+自身浓度猝灭机理分别为电偶极-电偶极和电偶极-电四级相互作用。     

有序介孔Al2O3:RE3+的制备及Gd3+对Eu3+的能量传递

以P123为表面活性剂,异丙醇铝为铝源,用简易溶胶-凝胶法,获得了单掺和双掺Gd3+,Eu3+的介孔氧化铝组装体.用广角X-射线衍射仪(WAXD)进行了物相分析;小角X-射线衍射仪(SAXD)、比表面仪进行了孔结构分析和形貌表征;研究了组装体的发光性能并发现Gd3+对Eu3+有能量传递作用,并分析了能量传递过程.     

Ce3+、Tb3+离子及Ce3+-Tb3+离子对在Sr4Si3O8Cl4基质中发光的研究

研究了Ce³⁺、Tb³⁺、离子及Ce³⁺-Tb³⁺离子对在Sr₄Si₃O₈Cl₄基质中的发射光谱和激发光谱。初步讨论了Ce³⁺、Tb³⁺离子之间发光敏化的机理。     

Ca2+、La3+及Eu3+对NaDC胶团的作用

在水溶液中将脱氧胆酸钠（ＮａＤＣ）分别与ＣａＣＬ２、ＥｕＣｌ３及ＬａＣｌ３反应,改变反应物浓度和配比,合成了系列脱氧胆酸络全物。利用红外光谱（ＦＴＩＲ）、元素分析、ＩＣＰ分析及Ｘ身材线粉末衍射谱,对它们的组成和结构进行了研究。结果表明：水溶液中ＣａＣｌ２与ＮａＤＣ的反应不是简单离子间的反应,改变其反应物浓度和配比,生成组成和结构不同的络合物;而ＬｎＣｌ３与ＮａＤＣ反应时,反应物浓度和配比的改变不影     

Dynamics of the O(3P) + CH4 → OH + CH3 reaction is similar to that of a triatomic reaction

The O((3)P) + CH(4) reaction has been investigated using the quasi-classical trajectory (QCT) method and an ab initio pseudotriatomic potential energy surface (PES). This has been mainly motivated by very recent experiments which support the reliability of the triatomic modeling even at high collision energy ( = 64 kcal mol(-1)). The QCT results agree rather well with the experiments (translational and angular distributions of products); i.e., the ab initio pseudotriatomic modeling "captures" the essence of the reaction dynamics, although the PES was not optimized for high E(col). Furthermore, similar experiments on the O((3)P) + CD(4) reaction at moderate E(col) (12.49 kcal mol(-1)) have also been of a large interest here and, under these softer reaction conditions, the QCT method leads to results which are almost in quantitative agreement with experiments. The utility of the ab initio pseudotriatomic modeling has also been recognized for other analogous systems (X + CH(4)) but with very different PESs.     

Analysis of the long range potentials of the X 1Σ+ and a 3Σ+ states of NaK

The difference in energy between the singlet and triplet states of NaK dissociating to Na(3s) and K(4s) is found from experimental data and from pseudopotential calculations. The contributions of various one- and two-electron integrals are evaluated, illustrating the present ambiguity over the exchange integral and the exchange interaction terms.     

Semiempirical calculation of the CH4 + CH3 · → CH3 · + CH4 radical-reaction potential surfaces in a basis of frontier orbitals

A semiempirical approach is suggested to describe potential-energy surfaces (PESs) of some radical reactions in the zero-differential overlap (ZDO) approximation. An incomplete basis set is used including only frontier (single-filled) radical molecular orbitals (MOs) depending on geometrical parameters. All possible configurations are taken into account. The parameter selection techniques are analyzed. The approach is applied to PES calculation of the CH₄ + CH₃ · CH₃ · + CH₄ reaction. Some points of the PES are verified by a nonempirical method using the perturbation theory and taking into account the correlation energy. The relaxation energies are calculated. The one-center parameters are determined nonempirically from the CH₃ + CH₃ ·, and CH₃ ^– energetics. The two-center parameters are found by modeling the CH₄ CH₃ · + H and C₂H₆ 2CH₃ reactions in the same single-orbital approximation. The energy parameters of the reactions considered are overestimated by 10%, whereas the geometrical parameters are under-estimated by 15%. Further, a comparative analysis of the Hartree-Fock solutions and those including correlation interactions (CIs) is given. The variations in the spin and charge densities on the reaction centers are considered.Institute of Chemical Kinetics and Combustion, Academy of Sciences of the USSR, Siberian Branch, Novosibirsk. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 4, pp. 499–506, July–August, 1991. Original article submitted February 10, 1989.     

KMgF3:Ce3+,Tb3+纳米粒子中Ce3+→Tb3+的发光及能量传递

利用微乳液方法,合成了铈、铽共掺杂的氟镁钾纳米粒子,研究了体系中Ce3+→Tb3+的发光特性以及它们之间的相互作用,结果表明KMgF3:Ce3+Tb3+纳米粒子中存在Ce3+→Tb3+的能量传递过程,即Ce3+可以将吸收的能量直接传递给Tb3+离子,使得Tb3+的绿色发光强度大为增加.     

The R3O+···H+ hydrogen bond: toward a tetracoordinate oxadionium(2+) ion

Oxatriquinanes are tricyclic oxonium ions which are known to possess remarkable solvolytic stability compared to simple alkyl oxonium salts. Their rigid, hemispherical structure presents an oxygen at the apex of three fused five-membered rings. While trivalent oxygen species like these have been well described in the literature, the ability of oxygen to enter into a fourth covalent bonding relationship has been visited in theory and suggested by the outcome of certain reactions conducted in superacidic media, but has never been established by the characterization of a stable, persistent R(3)OH(2+) or R(4)O(2+) ion. In this study, the nucleophilicity of the oxatriquinane oxygen was evaluated first by a series of protonation studies using the Br?nsted superacid H(CHB(11)Cl(11)) both in the solid state and in liquid HCl solution. The interaction of the oxatriquinane oxygen with a bridging carbocation was also examined. A strong case could be made for the occurrence of hydrogen bonding between H(CHB(11)Cl(11)) and oxatriquinane using IR spectroscopy. Under the most forcing protonation conditions, the oxatriquinane ring is cleaved to give a bridged, dicationic, protonated tetrahydrofuran-carbenium ion.     

Pr3+或La3+与克拉红霉素对大肠杆菌的协同作用

用LKB-2277生物活性检测系统采用停流法于37℃测定了克拉红霉素及克拉红霉素分别与Pr(NO3)3和La(NO3)3混合后,对大肠杆菌生长抑制作用的热效应变化.根据热动力学模型进行了定量解析,得到了各体系的克拉红霉素浓度c与大肠杆菌生长速率常数k之间关系式及其半抑制浓度Ic50.克拉红霉素:k=0.03106-1.273×10-3cIc50=8.81μg·mL-1(0.5～20μg·mL-1)克拉红霉素+Pr3+:k=0.02967-1.332×10-3cIc50=7.38μg·mL-1(1～15μg·mL-1)克拉红霉素+La3+:k=0.02741-1.194×10-3cIc50=6.34μg·mL-1(1～15μg·mL-1)微量热结果不仅表征了克拉红霉素的抗菌活性强于红霉素,Pr3+或La3+与克拉红霉素协同作用也使抗菌活性增强,而且反映了不同药物作用下细菌的生理、生化和代谢过程热动力学特征的变化.