2002 Vol. 15, No. 4

Article
So far, metastable Singlet oxygen is the only electronic excited state molecule that can be efficiently produced simply by a chemical reaction. To examine the proposal for a chemical laser of near-visible range by using the higher excited state oxygen O2 (b1Σ) which is generated through two O2 (1△) energy pooling, we de signed and studied a jet singlet oxygen generator with chlorine gas flow rate of 3-10 mmole/s. The O2(1△) concentratron, Cl, utilization rate and water content are measured using different injectors at different chlorine flow rate, cold trap temperature. We find that the optimum cold medium temperature is -140℃ to -150℃ when the trap is made of PVC. This result is explained by the competition between O2(1△) quenching and H2O freeze on wall of the trap. In optimum conditions, the water vapor pressure in the gas output can be reduced to as low as 4 Pa, which is reported for the first time.
The dynamics of the Cl + HD reaction has been studied by means of quasiclassical trajecrory calculations on both BW2 and G3 potential energy surfaces. The calculations show the product rotational alignment is sensitive to the potential energy surfaces and mass factors of reaction system. While the calculated product polarization on BW2 potential energy surface seems stronger than that on G3 potential energy surface for two products and the rotation of the DCl product is more strongly aligned in comparison with the HCl product in all cases. And also the calculations show the effect of the reagent rotational excitation on reactivity for both surfaces is significantly different. The initial rotational excitation has a positive influence on the reactivity for the Cl + HD reaction from calculations on the BW2 surface, while the effect of the reagent rotational excitation on reactivity is negative for G3 surface.
There action mechanism CH(X2Π)+NNO is investigated at the level of G2(B3LYP/MP2/CC). The equilibrium geometries, harmonic frequencies and energy of various stationary points on the potential energy surfaces have been calculated in the lowest dublet states. It is found that there are two reaction mechanisms. The intermediate HC( N)NO is first formed through a composite process, and then it will dissociate to HCN+NO, which is one of the most primary reaction channels. HC inserts into the NO bond, and produces an activated intermediate HC(O)NN over a barrier of 38.9 k J/mol. Then, it is flowed by five product channels, and one among them is rather important, i.e. CO+HNN.
The energies, equilibrium structures and vibration frequencies of HO,、HO and HO, have been calculated using both the density function theory (DIFT) at B3LYP/6-31G (d ) level and the second-order Moller-Plesset perturbation theory at MP2/6-31G(d) level. The B3LYP calculated ionization energy of neutral HO, radicals is 11.1 eV, which agrees very well with experimental ionization energy 10.9 eV. The calculated of HO by B3LYP method agree well with reported experimental results. We also discussed the features of photoelectron energy spectroscopy in photoionization of HO, neutral radical and in photodetachment of negative HO.
Four methods (B3LYP, B3PW91,PW91PW 91,SVWN) of density functional theory with the polarized split-valence basis sets 6-311+G(3d,f) have been performed to further investigate the stable structures and the spin multiplicities for Al5,Al5-,and Al5+ clusters. For each of Al5,Al5-,and Al5+ clusters five possible structures with different spin multiplicities have been investigated respectively. Some new characteristics concerning their stable structures and spin multiplicities have been found. The stable structures obtained by four DFT methods consistently are; planar C2v-p structure with doublet state(ground state) and three-dimensional C2v-3d structure with quartet state for neutral Al5; planar C2v-p structure with single state for anionic Al5- (in the sense of vibrational averaging); three-dimensional C2v-3d structure with singlet state (ground state) and planar C2v-p structure with triplet state for cational Al5+. The adiabatic can dvertical election detachment energies ( ADE,V DE) of anionic Al5, the adiabatic and vertical ionization potentials ( AIP, VIP) of neutral Al, have been computed using the four DFT methods respectively. The comparison between presently calculated results and available experimental data as well as the previous theoretical computations has been made. The present results are in good agreement with experimental data. The comparison among calculated results obtained by the four DFT methods are also made. For general local minima or saddle points on a potential energy surface conclusions obtained by the four DFT methods arc consisted at basically, but for complicated local minima or saddle points conclusions obtained by the four DFT methods are sometimes different. It needs to further study to determine which method is relatively reliable
The Vehicle exhaust gas generally contains nitrogen oxides and the fossil fuel which do greatly harm to air environment. Although the use of catalytic converters for the vehicle gas has resulted in considerable progress in the past twenty years, a theoretical framework for explaining the experimental observations is still lacking. We use the IJBI-QEP method to analyze the chemisorption species and calculate the energy of elementary reactions on six metal single crystal surfaces, Pt(III),Pd(III),Rh(III),Ag(III),Cu(III) and Ni(III). It will help us to realize the reaction mechanism and choose the best suitable catalysts. The sequence of chemisorption heat for N0, is Ni>Rh>Cu>Pd>Pt>Ag. The dissociation of N 0,de creases along the series Rh=Ni>Cu>Pd>Pt>Ag. The decomposition of NO can easy happen via NiO intermediate. From calculations at low coverage, we can see two possible pathways of N0, reduction, the direct dissociation and CO-aided dissociation. At high coverage, however, CO-aided dissociation is main pathway. For complete oxidation of carbon monoxide based catalysts may Pt, Pd, Ag and Cu are fine catalysts, but both Ni and Rh can not promote it. The Ni-Cu replace the noble metal catalysts (PI-Pd-Rh)
The chemical shift δ is the most important parameter in analyzing NMR spectra. It is the relative value of the sample's shielding (σ-) related to the reference's shielding (σ-ref). The reference (standard) is usually tetramethylsilane (TMS) for 1H and 13C. In quantum chemistry ab initio calculation, it is necessary to calculate the absolute shielding (σref), which has been calculated by different levels of theory and methods. The calculated results are fundamentally consistent with the experimental values.
Structural properties of Cu-Ni alloy are studied using MD simulation with EAM potential function. The FZ partial structure factor exhibits that Cu content has a small effect on it and the same holds true for bonded pairs and bond orientation order parameters, which indicates that the structure of Cu-Ni alloy isn't sensitive to its component. FZ partial structure factor of liquid Cu-Ni alloy is compared with that from Waseda, and they agree well with each other, which shows that EAM potential function can correctly describe the structural properties of Cu-Ni alloy, and also that the results of our MD simulation are reliable. In rapid cooling process, the second peaks of their pair distribution function from other Cu-Ni alloy split in two, indicative of amorphous structure; while the pair distribution function of Cu-Nim alloy exhibits the characteristic of crystalline. The bonded pairs, bond orientation order and effective diffusion coefficient of Cu-Ni alloy show that Cu-Ni alloy form shep crystalline at rapid cooling process.
The density profile of hard sphere fluid confined in two parallel hard walls was studied by using Rosenfeld Density Functional Theory (DFT) and Molecular Dynamics (MD) simulation method. By comparing the results of the two methods, we found that Rosenfeld density functional gives the same results as of MD simulation at larger separations of the walls, when the wall separation becomes smaller, differences of the two methods are showed up. The structures of the density distributions are also discussed.
A model to describe the structure of magnet or heological fluid (MRF) driven by rotating fields is presented. The model explains the phenomena of the radius of the layer structure changing with the rotating frequency, the natephenomena of the thickness of the layer changing with the modulus of the applied field, the factors that domi the phase lag of the structure, Al the results agree with the experimental results presented in current papers
The influence of 10 nonvolatile solutes on boiling point of methanol-tetrahydrofuran azeotrope was determined by means of isobaric vapor-liquid equilibrium experiments. Based on classical thermodynamics a conclusion of universal significance was derived, i. e. , a little nonvolatile solute always causes the elevation of azeotrope's boiling point irrespective of the variation of its vapor composition. It is in agreement with the experimental results and the relevant reports in the literature without exception.
A new two dimensional zinc complex was reported. This compound was synthesized under solvothermal condition by using THF as solvent. The crystal structure was determined by using single crystal X-ray diffraction. Crystal data: Zr', (B DC)( D ABCO)( H 20)z, monoclinic, space group C 2/c,a =10.871(17),b=19.10 (3),c=7.15 5(川,a= 90,口二115.99(3),Y=90,Z 二8,V 二1335(4),Dr二2.085岁cm3,R二0.08 58. This compound has two-dimensional network structure. Each zinc metal center was coordinated by two DABCO, two BDC and one water molecule. DABCO and BDC ligands bridge to two zinc atoms, respectively. The extension of this〔。-ordination result in a two-dimensional network and form a 7.16 x 9.98A zporous structure. It was interesting to find that the 2-dimensional was an interpenetrated structure formed by two coordinate polymer networks. This kind of structure is very rare in the coordinate compounds. The m-m interaction between the phenyl group of BDC was believed to the key of the growth of this coordination network.
By measuring the equilibrium and cyclic 1r-Aisotherms and dynamic elasticities of ocladecylamine monolayets on the subphases of water and CdGl, solution, it is showed that Cdr' added into the subphase can enhance the condensability of liquid-like monolayer but decrease that of the solid-like monolayer. On both of the subphases, the liquid-like monolayer shows reversible, while the solid-like monolayer is irreversible. This can be attributed to the hydrogen bond between ocladecylamine molecules on water and the complexation of ocladecylamine molecules with Cd2' on CdCI, subphase. In highly compressed monolayer on CdClz subphase, some metal complex comes into being and forms stable aggregate on the surface of subphase. The aggregation can also occur between octadecylamine molecules in the solid-like monolayer on pure water. The difference between the static and dynamic elasticity of the monolayer shows that dynamic oscillation with low frequency and small amplitude would weaken the complexation between octadecylamine molecules and Cd2.
A new silicon-based luminescence material-C( F ilm)/S i(S iO,)(nanometer particles)/C ( F ilm) (abbr. C(F)/Si(SiO,)(N)/C(F))is made by sputtering silicon nano-particles on the amorphous carbon film in Ar gas firstly, then depositing amorphous carbon film on silicon nano-particles layer in vacuum. Finally, it has been annealed at 400,650 and 75090 for Ihr espectively. The photoluminescence ( PL) of the sample is tested by fluorescence spectrophotometer. Excited by 250 nm UV-light, the unannealed sample gives a strong PL, band around 398n or( 3.12 e V). After annealed at 6 5090,the sample gives not only PL, band, but also gives another strong PL, band around 360 nor (3.44 eV). The shape and peak position of PL, and PL, are independent on annealing temperature and excited wavelength. On the contrary,the intensities of PL, and PL, are strongly dependent on it; their intensities are the lowest after the sample annealed at 40 0`0 and the highest after annealed at 65090. The shorter the excited wavelen is; the stronger their intensities are. The intensity of PL, band is directly proportional to the ratio of S' 02/S"R elated to the configuration analysis tu01,the sere sultssuggest that the excitation of photonso f PL, band occursin side S iO, nanometerp articles, and the emission of photonscomes from thed effects at the interface between SiO, and Si. PL, band is due to electron-hole recombination inside SiC manometer particles.