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1.
A laser pulse-and-probe method has been used to determine the nascent vibrational populations in NO( v=0–4) and O 2( v=6–11) formed in the thermal reaction: O( 3P) + NO 2 → O 2( v) + NO( v). A frequency-tripled Nd: YAG laser is used to photolyse NO 2, diluted tenfold in Ar, and laser-induced fluorescence spectroscopy in the NO A 2Σ +-X 2Π and O 2 B 3Σ −u -X 3Σ −g electronic band system is used both to follow the kinetics of individual vibrational states and to determine the nascent vibrational distributions. The majority of the NO product is formed in v = 0 and the average vibrational yield is ≈ 4.6%. The O 2 populations fall monotonically from v = 6 to 11 in a distribution close to what is expected on prior grounds. Based on a surprisal analysis, the average vibrational energy yield in O 2 is ≈ 26%. The nature of the reaction dynamics is discussed. 相似文献
2.
The A 2Π u-X 2Π g electronic emission spectrum of I 2+ has been recorded at a low rotational temperature in a crossed molecular beam/electron beam apparatus. Six vibrational sequences with five or more members have been assigned to progressions in ν′, giving ω′ e = 122±8 cm −1, but a full vibrational analysis has not been possible. It is not known whether this is due to the relatively poor resolution (≈5 cm −1) at which the spectrum has been recorded or because the A 2Π u state is perturbed in one or both spin-orbit components. Existing data on the A state of I 2+ are reviewed. 相似文献
3.
The luminescent properties of divalent europium complexes with crown ether, azacrown ether, N-pivot-azacrown ether, and cryptand in methanol or water have been systematically investigated under UV irradiation. These divalent europium complexes show greatly enhanced emission from 417 nm to 488 nm in the visible blue region in comparison with that of the methanol solution of EuCl 2. The aqueous solution of EuCl 2 is non-luminescent. This obvious distinction in luminescent properties between the macrocyclic ligand-coordinated divalent europium and uncoordinated divalent europium is attributed to the “insulation effect” of Eu 2+ ion from the solvent molecules of CH 3OH and H 2O by the macrocyclic crown ether or cryptand encapsulation to divalent europium. Moreover, these macrocyclic ligands provide an additional restriction to the electronic charge expansion of the excited Eu 2+. This also contributes to the enhancement of the Eu 2+ luminescence. Among all the investigated macrocyclic ligands, 15-crown-5 (15C5) affords the largest enhancement to the Eu 2+ emission. The intensity of the Eu 2+–15C5 complex is 690 times that of the EuCl 2 methanol solution with the same Eu 2+ concentration. This special emission enhancement effect is related to the particular complex composition of 1:3 (Eu 2+:15C5) and corresponding configuration of Eu 2+–15C5 complex in methanol. Concerning the mechanism, the luminescence enhancement of divalent europium by complexation with these macrocyclic crown ether or cryptand ligands is found to be initiated from the decrease in non-radiative rate constant rather than from the increase in radiative one. The divalent europium complexes of methacrylate polymeric polyether derivatives such as 15C5-, 18-crown-6- (18C6), and cryptand [2.2.1]- or [2.2.2]-containing polymer and copolymer have also been prepared. Their luminescent properties in solid state have been studied to aim for practical application. As a similar situation to the simple polyether complexes, the divalent europium complex with 15C5-containing polymer or copolymer shows the largest luminescent enhancement effect. Its emission intensity reaches about 20% that of the commercial inorganic luminescence product CaWO4:Pb (NBS 1026). In addition, the doping effect of several divalent ions, namely Mg, Sr, Ba and Zn in polymeric complexes, has also been investigated according to the luminescence concentration quenching mechanism in solid state luminescence materials. The emission intensity of 15C5-containing polymer europium(II) complex is raised to twice stronger by doping of Zn2+ ion. 相似文献
4.
Large-scale MRD CI calculations assign to AlP the ground state X 3Σ − (9σ 23π 2) and a close-lying state 1 3Π (9σ3π 3) ( Te = 0.08 eV). Up to transition energies of 2.0 eV, other states are described by the configurations 9σ3π 3 (1 1Π), 8σ 23π 4 (1 1Σ +), 9σ 23π 2 (1 1Δ and 2 1Σ +) and 9σ3π 24π (1 5Π). The 2 3Π state, located at ≈ 2.30 eV, shows a shallow double minimum. Numerous perturbations are expected to induce predissociation upon 2 3Π. Multiplets arising from the occupation 8σ 23π 34π are clustered in the 3.25–3.50 eV region. Quintet states with the configuration 8σ9σ3π 34π are bound, with Te values (in eV) of 3.80 (1 5Σ +), 4.44 (1 5Δ) and 4.88 (3 5Σ −), respectively. The 9σ → 4s Rydberg members 5Σ − and 3Σ − lie in the 4.58–4.72 eV energy region. The first ionization potential (ionization to X 4Σ − of AlP +, 9σ → ∞) is estimated to be 7.65 eV. Ionization to the 1 2Σ − and 1 2Π states of AlP + is suggested to occur between 8.0 and 8.8 eV. The dipole moments of X 3Σ −, 1 1Δ and 2 1Σ + are close to 1.0 D, whereas the 1 1Σ + state has μ = 3.49 D; 1 3Π and 1 1Π have dipole moments from 2.45 to 2.91 D. All low-lying states show a polarity Al +P −. Finally, the electronic structure and transition energies of AlP are compared with those of the isoelectronic species BN, AIN, and SiP +. 相似文献
5.
A novel bipolar stationary phase (HCPS–MO) was prepared by impregnation of hypercrosslinked polystyrene (HCPS) with methyl orange (MO; 4-dimethylamino-4′-sulfoazobenzene) and its ion-exchange properties were studied. Simultaneous separation of cations and anions on HCPS–MO is possible, although it behaves preferentially as a cation-exchanger. Unusual selectivity of HCPS-MO for alkali and alkaline-earth metal cations: Na ++K++4++ and Mg2+2+2+2+ was observed. The effect of temperature on retention of alkali and alkaline-earth metal cations was studied. Separation of Na+, K+, Rb+, NH4+, Cs+, Mg2+ and Ca2+ on HCPS–MO with diluted cerium(III) nitrate solution as an eluent in single run is presented. 相似文献
6.
The behaviour of the biacetyl molecule (BA) in a cold plasma, obtained by extraction of reactive species from a nitrogen plasma generated in a microwave discharge, is discussed. When the partial pressures of nitrogen and biacetyl are approximately equal ( pN2 ≈ 0.60 Torr, pBA ≈ 0.55 Torr), the emission of the 3A u--- 1A g transition of biacetyl is observed with a vibrational structure. On reaction of biacetyl with nitrogen cold plasma preferentially enriched in N 2(A 3Σ +u), an enhancement of the emission intensity of the phosphorescence of biacetyl is observed. The initiator of this transition is the triplet state BA( 3B u) which originates from an isoenergetic transfer from N 2(A 3Σ +u) according to the overall mechanism 相似文献
7.
采用密度泛函理论B3LYP方法计算了吡啶取代的Lindqvist型多酸(POMs)的线性(最大吸收波长, λmax)和非线性光学(NLO)[超瑞利散射(HRS)的第一超极化率, βHRS]性质, 探讨了其作为潜在阳离子检测剂的可能性. 金属离子吸附能计算结果表明, 吡啶取代的Lindqvist型多酸配体与金属离子之间均有较强的相互作用, 相互作用强度大小顺序为Ni 2+>Cu 2+>Co 2+>Fe 2+>Zn 2+>Mg 2+>Ca 2+. 电子光谱和 βHRS计算结果表明, 引入适当的供、 受电子基团对该多酸配体进行修饰可有效调节线性和二阶NLO性质; 同时, 吡啶取代的Lindqvist型多酸对7种金属离子(Cu 2+, Zn 2+, Ca 2+, Mg 2+, Ni 2+, Co 2+, Fe 2+)表现出了不同的检测行为. 相似文献
8.
Gaussian-2 ab initio calculations were performed to examine the six modes of unimolecular dissociation of cis-CH 3CHSH + (1 +), trans-CH 3CHSH + (2 +), and CH 3SCH 2+ (3 +): 1 +→CH 3++ trans-HCSH (1); 1 +→CH 3+ trans-HCSH + (2); 1 +→CH 4+HCS + (3); 1 +→H 2+ c-CH 2CHS + (4); 2 +→H 2+CH 3CS + (5); and 3 +→H 2+ c-CH 2CHS + (6). Reactions (1) and (2) have endothermicities of 584 and 496 kJ mol −1, respectively. Loss of CH 4 from 1 + (reaction (3)) proceeds through proton transfer from the S atom to the methyl group, followed by cleavage of the C–C bond. The reaction pathway has an energy barrier of 292 kJ mol −1 and a transition state with a wide spectrum of nonclassical structures. Reaction (4) has a critical energy of 296 kJ mol −1 and it also proceeds through the same proton transfer step as reaction (3), followed by elimination of H 2. Formation of CH 3CS + from 2 + (reaction (5)) by loss of H 2 proceeds through protonation of the methine (C H) group, followed by dissociation of the H 2 moiety. Its energy barrier is 276 kJ mol −1. On both the MP2/6-31G* and QCISD/6-31G* potential-energy surfaces, the H 2 1,1-elimination from 3 + (reaction (6)) proceeds via a nonclassical intermediate resembling c-CH 3SCH 2+ and has a critical energy of 269 kJ mol −1. 相似文献
9.
Large-scale ab initio coupled cluster and multi-reference configuration interaction calculations (MRD-CI) are carried out to determine the equilibrium geometry and the vertical electronic spectrum of linear C 5+. Contrary to prior theoretical estimates we find three low-lying states within an energy range of 0.3 eV: 2Σ u+, 2Σ g+ and 2Π g and a symmetric arrangement of nuclei. Transitions from 2Σ u+ to these low-lying states are dipole-allowed; sizeable oscillator strengths are computed for the 2Π +g←X 2Σ u+ transition at 2.62 eV and the 2Σ g←X 2Σ u+ transition at 3.36 eV and should give a guide to spectroscopic identification of linear C 5+. 相似文献
10.
The effects of doping of Co 3O 4with MgO (0.4–6 mol%) and V 2O 5 (0.20–0.75 mol%) on its surface and catalytic properties were investigated using nitrogen adsorption at −196°C and decomposition of H 2O 2 at 30–50°C. Pure and doped samples were prepared by thermal decomposition in air at 500–900°C, of pure basic cobalt carbonate and basic carbonate treated with different proportions of magnesium nitrate and ammonium vanadate. The results revealed that, V 2O 5 doping followed by precalcination at 500–900°C did not much modify the specific surface area of the treated Co 3O 4 solid. Treatment of Co 3O 4 with MgO at 500–900°C resulted in a significant increase in the specific surface area of cobaltic oxide. The catalytic activity in H 2O 2 decomposition, of Co 3O 4 was found to suffer a considerable increase by treatment with MgO. The maximum increase in the catalytic reaction rate constant ( k) measured at 40°C on Co 3O 4 due to doping with 3 mol% MgO attained 218, 590 and 275% for the catalysts precalcined at 500, 700 and 900°C, respectively. V 2O 5-doping of Co 3O 4 brought about a significant progressive decrease in its catalytic activity. The maximum decrease in the reaction rate constant measured at 40°C over the 0.75 mol% V 2O 5-doped Co 3O 4 solid attained 68 and 93% for the catalyst samples precalcined at 500 and 900°C, respectively. The doping process did not modify the activation energy of the catalyzed reaction but much modified the concentration of catalytically active constituents without changing their energetic nature. MgO-doping increased the concentration of CO 3+–CO 2+ ion pairs and created Mg 2+–CO 3+ ion pairs increasing thus the number of active constituents involved in the catalytic decomposition of H 2O 2. V 2O 5-doping exerted an opposite effect via decreasing the number of CO 3+–CO 2+ ion pairs besides the possible formation of cobalt vanadate. 相似文献
11.
Single and multiple photon processes are identified in the 193 nm excimer laser photolysis of CS 2. CS(X 1Σ +, υ = 1 to 5, J = 5 to 45) is observed by dye laser induced fluorescence of the A 1Π ↔ ; X 1Σ + transition, following the single photon 193 nm photolysis of CS 2. Multiple photon 193 nm generation of CS fragment emission from 620 to 170 nm is also reported. A partial assignment of the emission spectrum identifies fluorescence from the CS A′ 1Σ + and A 1Π states. 相似文献
12.
The radiative lifetimes of the b 1Σ + and a 1Δ states have been evaluated by perturbation expansions including X 3Σ −, a 1Δ, b 1Σ +, 1 3,1Π, 2 3,1Π, 2 3Σ − and 2 1Σ + states. All wavefunctions result from large MRD CI calculations. The b—X transition is dominated by the parallel transition moment; it is found to be much stronger than the a—X transition. The calculated radiative lifetimes of τ( 1Σ +)=18 ms, τ( 1Δ)=2.2 s for NF and τ( 1Σ +)=2.5–3.5 ms for NCl are in good accord with corresponding experimentally deduced values. The lifetime for the a 1Δ state in NCl is found to be τ( 1Δ)=1.1 s, ie. much longer than derived from a recent experiment. Its magnitude is consistent with the τ(b 1Σ +)/τ(a 1Δ) ratio of similar systems and with the decrease in lifetime from NF to NCl and is thus believed to be quite reliable. A detailed analysis of all contributions of the perturber states to the transition mechanism is made and comparison with the related data in SO, O 2 and S 2 is undertaken. The b-a transition probability dominated by the quadrupole transition is fairly constant in all the systems in the order of A = 0.013 (NF) - 0.0013 (S 2) s −1. 相似文献
13.
Ion-pair formation constants ( KMLA mol −1 dm 3) of Na +– and K +–18-crown-6 ether (18C6) complexes with MnO 4− in water (w) were determined potentiometrically at 25 °C. Simultaneously, extraction constants ( Kex mol −2 dm 6) of the permanganates with 18C6 from w into 1,2-dichloroethane at 25 °C were obtained from the spectrophotometric determination of distribution ratios of the permanganates. These Kex values were divided into KMLA and other three component equilibrium constants and thereby extraction-selectivity and -ability were discussed in comparison with corresponding metal picrate–18C6 extraction systems reported before. 相似文献
14.
Excited states of the Fe 2 molecule are investigated in high resolution by means of 1 XUV + 1 UV resonance-enhanced photo-ionization. Perturbations in the C 1Σ +u valence state and the spectroscopy of the H 1Π u Rydberg state are studied in detail. It is shown that F 2 molecules may be state-selectively detected with a sensitivity of 5 × 10 7 particles per cm 3. 相似文献
15.
The stationary points characterizing the potential energy profiles of the complex processes of the M +(M=H, Li, Na, K) and NF 3 were investigated by QCISD and B3LYP in conjunction with the 6-311+G(2d,2p) basis set. The optimized geometries and NBO analysis indicate that the complexes of M +(M=Li, Na, K) and NF 3 exist as ion-dipole molecules. But for H + complexes, there are two stable isomers NF 3H + and NF 2+–HF. The interaction distances of isomers follow the sequence H +< Li +< Na +< K +. The calculated affinity energies of the most stable isomers of H +, Li +, Na +, and K + complexes exceed 20.1 kJ/mol, and these values suggest that the M +–NF 3 (M=H, Li, Na, K) complexes could be observed as stable species in gas phase, which supports Fujii's proposal that Li + ion attachment mass spectrometry can serve as a conceivable technique to quantify the emissions of the NF 3. 相似文献
16.
Translational-energy spectroscopy was applied to collisional-excitation and charge-inversion reactions of CF +, CCl +, SiF + and SiCl + in order to gain energetic and bond-length information about the anionic and excited-cationic states of the title molecules. The excitation spectra revealed that the ã 3Π state, known in CCl + and SiCl +, has a term energy of 4.85 ± 0.15 eV in CF + and 4.70 ± 0.20 eV in SiF +, while the 1 1Π state, known in CCl +, is not below the dissociation threshold in CF +, SiF + and SiCl +. These data, and bond-length estimates for the ã 3Π states, are consistent with documented ab initio predictions except for re of CF +(ã 3Π) which seems to be larger than 1.21 Å. Charge-inversion spectra indicated that beams of monohalide cations formed from the tetrahalides, contained substantial proportions of ã 3Π-state ions, and, in the case of CCl, SiF and SiCl, the broadness of spectral peaks was taken as evidence for the stability of the ã 1Δ-state anion. Adiabatic electron affinities were deduced to be 0.49 ± 0.15 eV, 0.89 ± 0.20 eV, 1.34 ± 0.30 eV and 1.40 ± 0.30 eV for the title molecules, respectively. 相似文献
17.
Mg +—Ar ion—molecule complexes are produced in a pulsed supersonic nozzle cluster source. The complexes are mass selected and studied with laser photodissociation spectroscopy in a reflectron time-of-flight mass spectrometer system. An electronic transition assigned as X 2Σ + → 2Π is observed with an origin at 31387 cm −1 (vac) for 24Mg +—Ar. The 24Mg +—Ar spectrum is characterized by a 15 member progression with a frequency (ω′ e) of 272 cm −1. An extrapolation of this progression fixes the excited state dissociation energy ( D′ o) at 5552 cm −1. The corresponding ground-state value ( D″ o) is 1270 cm −1 (3.6 kcal/mol). The 2Π
,
spin—orbit splitting is 76 cm −. 相似文献
18.
The electronic dipole transition moment functions of the A 2Π-X 2Σ +, B 2Σ +-X 2Σ + and B 2Σ +-A 2Π transitions and the dipole moment function of the X 2Σ + state of CO + have been calculated using large contracted CI wavefunctions. The computed transition moment functions together with experimental potential energy curves were used to obtain radiative lifetimes of the excited electronic states B 2Σ + and A 2Π. Radiative lifetimes of vibrational levels of the X 2Σ + state were derived from the calculated dipole moment function. The high-frequency deflection technique was used to obtain radiative lifetimes of the ν′ = 0, 1,2 and 3 vibrational levels of the B 2Σ + state and also radiative lifetimes of individual rotational levels of ν′ =0. The calculated radiative lifetimes are shorter than the measured ones by about 10%. The experimental ν′ dependence is reproduced by theoretical calculation. The calculated radiative lifetimes for the A 2Π state are in excellent agreement with lifetimes measured with an ion trap technique. 相似文献
19.
A mixture of NF 3 and Ar is passed through an rf discharge in a flow-system to produce, among other species, F and NF 2. When H 2, D 2, or CH 4 are added downstream, reactions with F atoms produce vibrationally excited HF or DF together with H, D, or CH 3. The latter free radicals can react with NF 2, probably by an elimination reaction to produce electronically excited NF: NF 2( 2B 1) + H(D, CH 3) → HF *(DF * + NF(a 1Δ). A vibrational-to-electronic energy transfer process between the products of this reaction then produces the next higher state of NF: HF(ν 2) + NF(a 1Δ) → HF(ν−2) + NF(b 1Σ +). A similar transfer process has also been found between the electronically excited a 1Δ states of O 2 and NF: O 2(a 1Δ) + NF(a 1Δ) → O 2(X 3Σ −) + NF(b 1Σ +). The H or D atoms but not the CH 3 radicals are then found to react with either NF(a 1Δ) or NF(X 3Σ −) to produce electronically excited N( 2D) atoms, which in turn react with the NF(a 1Δ) molecules to produce N 2(B 3Π g). The observed nitrogen first positive radiation has been demonstrated to be produced entirely by this reaction mechanism rather than by the N( 4S) recombination that accounts for the Rayleigh afterglow. In addition, the occurrence of the reaction N( 2D) + N 2O → NO(B 2Π r) + N 2 (X 1Σ +g) has been verified. Finally we have observed emission at 3344 Å, which we attribute to the NF(A 3Π), which has not been previously reported. 相似文献
20.
The spectrofluorimetric determination of Fe 3+ using salicylic acid as an emission reagent has been investigated by measuring the decrease of fluorescence intensity of salicylic acid due to the complexation of Fe 3+–salicylic acid. An emission peak of salicylic acid, which is decreased linearly by addition of Fe 3+, occurs at 409 nm in aqueous solution with excitation at 299 nm. The determination of the ferric ion is in the range 1×10 −6–10×10 −6 M Fe 3+ (0.0558–0.558 μg/ml) and the detection limit is 5×10 −8 M. The quenching effect of Fe 3+ on the fluorescence intensity of salicylic acid may be considered on the basis of complexation between salicylic acid and Fe 3+. The effects of foreign ions were investigated. 相似文献
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