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1985 Volume 1 Issue 1
Active intermediates in the photolysis processes of compounds Ph_3M (M=N, P, As, Sb, Bi) have been studied with the combination of spin trapping technique, column chromatography and ESR spectrascopy. From the hyperfine structures of the ESR spectra of the spin adducts formed between active intermediates and spin trapping reagents such as phenyl tert-butyl nitrone (PBN), nitrosobutane(t-BuNO) or nitrosodurene (ND), the free radical Ph. has been identified in the photlysis of Ph_3M (M= P, As, Sb, Bi) and Ph_2M·+Ph·. As the average bond energies of Ph—M decrease in the order Pb—P>Ph—As>Pb—Sb>Ph—BiPh_2M· (M=As, Sb, Bi) decompose much easy than that of Ph_2P·, so they could not be observed in out experiment.
The Solvent effect on absorption spectra and laser induced emission fluorescence spectra of 16 cyanine dyes in 18 solvents has been studied. The results show that the shift of absorption peak Δσ_A and the energy difference (σ_A-ν_F) depend not only on the refractive index of the solvent used, but also on its dielectric constant. Therefore, tne new functions f(n,ε)=(n~2-1/2n~1+1)+α(ε-1/ε+2) and f(n,ε)=(ε-1/2ε+1)-(n~2-1/2n~2+1) are used instead of the Bayliss function f(n)=(n~2-1/2n~2+1) for absorption and fluorescence respectively. The effect of sovlent polarity on the position and intensity of the fluorescence peak and the order of ~1(n, π~*) and ~1(π, π~*) states of these dyes has also been studied in this work.
The adsorption and reaction of CO and H_2O on Ni catalyst were studied using infrared spectroscopy. Some valuable results were obtained.
1. Adsorption of H_2O and CO
Two types of adsorbed CO on Ni catalyst were identified by IR spectroscopy, the linear state (2060 cm~(-1)) and bridged state (1960 cm~(-1)). Above 200 ℃, disproportionation reaction of CO could occur, forming CO_2 and surface carbon.
A wide absorption band at 3600—3100 cm~(-1) was observed when H_2O was adsorbed on the catalyst. The band belongs...
The hydrogen spillover effect of Pt-NaY/HY system has been studied using the exchange reaction of deuterium with hydroxyl groups by IR spectroscopy. The Pt-NaY catalyst used was prepared by impregnation of NaY zeolite with chloroplatinic acid. HY zeolite was prepared by NH_4~+ exchange of the same NaY zeolite followed by thermal decomposition. About 12.5% Pt metal dispersion and a Pt particle size of about 9.0 nm were determined from H_2 Chemisorption data at 0 ℃.
The wafer of HY zeolite used in the IR cell was mixed with a small amount of the catalyst in such a way that the Pt catalyst dispersed only around the periphery of the wafer.
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Thermal desorption spectra for oxygen chemisorbed on electrolytic silver have been obtained using a temperature programmed reaction (TPRS)technique with mass analysis in an ultrahigh vacuum (UHV) system. More than twenty times cycles of pretreatments were carried out at a partial pressure of oxygen equal to 1×10~(-3) torr and at 650 ℃ while desorption measurements were obtained in a total pressure enviroment 2-5×10~(-9) torr. For oxygen exposure 90 L three distinct species appear in the desorption spectra. Isotope-mixing, CO titration and kinetic behaviour studies lead to the following assignments: weakly molecularly chemisorbed oxygen (E_d=92 kJ mol~(-1), v=4.1×10~(11) s~(-1)), strongly chemisorbed stomic oxygen (E_d=134 kJ mol~(-1), v=4.7×10~(13) s~(-1)) and oxygen diffused to the bulk of silver (see Fig.2). Detailed information about the variation of states of adsobed oxygen with exposure, between 5 L and 10~8 L, have been obtained and for θ=0.2~0.6 a “break” of atomic oxygen desorption is also found, in agreement with other studies. The desorption of molecularly adsorbed oxygen exhibited complex kinetics due to lateral interactions between the adsorbed molecularly oxygen and stomic oxygen. It is suggested that the adsorption of molecularly oxygen due to the presence of surface impurities, such as sodium, carbon, sulfur etc.. The behavior of the desorption of bulk oxygen has been studied by isothermal dessorption technique. The result shows that the higher temperature of oxygen adsorption favors the diffusion of oxygen.
Recent experiments have indicated that vinylidene is a reaction intermediate when HCI is eliminated from a-chloro olefins in a three center mechanism.Theoretical studies have concentrated on the vinyhdene and its rearrangement to acetylene, i.e. on the reactant, transition state and the product, but not on the reaction path.
In this paper, based on ab initio(STO-3G)SCF MO, the IRC (intrinsic reaction coordinate) of this rearrangement reaction was found out by a numerical method proposed by Morokuma to solve the Fukui′s IRC differential equations. According to the IRC, in the course of the reaction, the reaction energy varies mainly with ∠H_aCC. The change of the relative positions of different atoms in the system along the reaction path has been discussed. ...
It has been Verified by XPS, IR, NMR and solvent washing that TiCl_4·2Et_2O complex is able to react with 3TiCl_3·AlCl_3 catalyst in solid phase as show in table (1—1), table (3—2) and Fig (2—1) — (2—4). The solid-solid reaction is as follows
TiCl_4·2Et_2O+2AlCl_3—→2AlCl_3·Et_2O+TiCl_4
After treatment with TiCl_4·2Et_2O complex the surface structure of the catalyst could be described approximately by a three layer model.
Properties of the catalyst are effected by the donor and acceptor components from whi...
Optical-optical double resonance multiphoton ionization(OODR-MPI)spectroscopy is a rapidly developing, versatile technique which should find wide applications in both molecular spectroscopy and molecular dynamics.
In an OODR-MPI study of CO, we irradiate the static sample cell by 2 pulsed dye laser beams. The first UV laser light (“pump beam”) resonantly pumps ground state CO to A~1∏ state via a 2-photon process. Then a second visible laser light (“probe beam”) excites CO A~1∏ to B~1∑~+. The excited B~1∑~. The excited B~1∑~+ molecule further under es ionization by absorbing one more UV photon, so the whole process follows a 2+1+1 photon scheme.
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A precision static oxygen bomb combustion calorimeter with thermistor thermometer was constructed in this laboratory. The experimental data was treated with electronic computer, the programme was designed by ourselves. The calorimeter was calibrated with benzoic acid of purity 99.999 percent, its energy equivalent is 12.6028±0.00114 kJk~(-1). Using this calorimeter, the standard energy of combustion of tris (hydroxy-methyl)-aminomethane (THAM) at 298.15 K was measured, its value was Δ_cu~°=-20.0303±0.0060 kJg~, in satisfactory agreement with that cited in literature (-20.0303±0.0034 kJg~(-1)), the reliability of this apparatus wa confided.
Sunlight may be converted into electrical or chemical energy by semiconductors composed of suitably doped polymers (e.g. polyaeetylene). The mobility of the dopant in the polymer is significant and the concentration of dopant is not uniform in the semiconductor polymer because of the electric field in the space-charge region. The theoretical treatment for traditional semiconductor, even the depletion layer approximation cermet be applied to this case. It is interesting to study quantitatively the distributions of concenrations of dopant and carriers as well as the electric potential and field. In order to search for polymer semiconductor material as photoelectrode of high performance, it is necessary to study quantitative relationships between the conversion efficiency and various parameters of the semiconductor bulk properties.
For the steady state of a planar n-type semiconductor illuminated by monochromatic light, the following six simultaneous differential equations can be formulated:
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The previous papers of the authors have shown that with modern theories of solution the extraction equilibrium distribution can be calculated by the thermodynamic models.
If the ion-association and idssociation equilibrium do not occur in the aqueous phase, it is suitable to use Pitzer′s equation for the activity coefficients of the single electrolyte and to use Frank-Thomson diffuse lattice theory for the activity coefficients of the mixed electrolytes.
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The modified n~+/p-Si photoanode had been prepared by ion sputtering first with thickness of 4.0 nm platinum and then by electroplating a thin W-Ni alloy film. It was found that when this photoanode was illuminated with anodic bias (at 1.0 V vs. 1N H electrode) under cyclic voltammetric conditions, the photocurrent density might reach 46.4 mA cm~(-2). It was clear that W-Ni film appeared an excellent catalytic action for oxygen evolution. The surface of n~+/p-Si photoanode modified by double metal films had also been studied using methods of scanning electron microscopy and x-ray photoelectron spectro-scopy.
