2001 Vol. 14, No. 2

The photodissociation of nitrosobenzene (C6H5NO) at 266nm has been studied by monitoring the nascent NO product using a one-photon laser-induced fluorescence (LIF) technique.The NO (X 2Π ν″=0→ A 2Σ+ ν′=0) ro-vibrational spectrum was obtained. The J" quantum numbers of NO (X, ν″=0) populated in the dissociation process have been assigned by comparing the experimental spectrum with the simulated spectrum. The rotational distributions with quantum numbers up to J″=50.5 were obtained. This means that the NO (X) fragments produced in the dissociation process are of highly rotational excitation. The probable photolysis mechanism is proposed for the photodissociation of C6H5NO at 266nm.
The multi-photon ionization processes of acetone in the range 243~263nm have been studied using mass-resolved excitation spectra. From the analysis to the excitation spectra and the mass peak widths of CH3COCH3+, CH3CO+ and CH3+, the photochemical reactions of acetone in this range are suggested as follows. The CH3COCH3+ signals in the shorter wavelength range of λ<255.67nm are due to the (1+1) photon ionization channels of acetone via (S1, T1) state of acetone. The fragment ion CH3+ comes from the dissociation of parent ion CH3COCH3+. The non-resonance spectral structure of fragment ion CH3CO+ comes mainly from the ionization of acetyl (CH3CO) produced by one-photon dissociation of acetone via (S1, T1) state. We also deduced the IP of (9.696±0.004)eV for acetone from the spectra of CH3COCH3+.
Using the Ni surface-catalyzed excitation method, we obtained the (0,0) electronic transition spectra of atmospheric oxygen band (b1Σg+→X3Σg-) from the recombination of ground state oxygen atoms O(3P) in flowing afterglow apparatus. We experimentally analysed the kinetic process of deactivation of O2(b) by the wall, which indirectly proved that the concentration of O2(b)changed in a nonsteady-state way in the flowing tube. Meanwhile, the formation mechanism of O2 (b) was simply discussed.
A multiple-pass geometry for simple structure and easy adjustment is designed ,which consists of only a concave mirror and a plane mirror. The stability condition of this optical system is worked out. A design procedure for maximum number of reflection is described that includes a consideration of input ray diameter and divergence angle. A 56-pass cell is constructed for Ti: sapphire ring laser photoacoustic spectrometer. The calculated spot pattern is in good agreement with the experimental observation. This technique is useful for photoacoustic spectroscopy and long path absorption.
The reaction of O(3P) atom with CH3 radical was studied by Density Function Theory (DFT) and ab initio MO methods. The optimized structure parameters, vibration frequencies and energy of each stationary point on its potential energy surface were computed by B3LYP theory. Results indicate that the abstraction of single H atom or formation of CH2O is the most significant channel of the reaction system, meanwhile CH2OH radical is more stable than CH3O due to the energy difference of 26.63kJ/mol. In addition, we proposed a possible explanation for the presence of CO product in some former experiments.
According to chemical bond theory and topological principle, 46 non-crystalline clusters NixZry (x:y=1∶2 or 2∶1, x+y≤9) have been examined and optimized by using quantum chemistry ab initio method. The calculation results show that for NixZry (x:y=1∶2) the lower-symmetry plane configurations are more stable than solid tri-prism configuration, and for NixZry (x:y=2∶1) it is reverse. The difference may be due to diverse valence electrons of transition metals∶ There is only 4 valence electrons in zirconium, so it enjoys at plane configuration of lower coordination number, and nickel (4d23d8) more fits to solid configuration.
Adaptive adjustment mechanism (AAM), which is used to control chaos, Utilizes neither prior knowledge of the system itself nor external control signals. By using this merit, we employ AAM mechanics to control a chaotic neuron. Varying adaptive parameter γ, we obtain a series of controlled chaotic orbits.
The mesoscopic dynamics of a chemical chaos model was studied by stochastic simulations. Ensemble simulations of the model showed that there are intensive intrinsic fluctuations in the unstable motion. However, due to the globally stable character of deterministic chaos, the ensemble points were limited to distribute overall the chaotic attractor. Furthermore, individual simulation runs keep quantitative character of the deterministic chaos.
Differential flow type reaction-diffusion equation for Selkov model is developed and the stability for uniform steady state is theoretically studied. The results show that there is convective instability when the flow rate φof auto catalyst B is greater than the critical value φc(φ>φc). Numerical simulations obtain the spatio-temporal structure of B in different time t and at different flow rate , respectively, which shows some special features, meanwhile the convective instability is also conformed.
With the model that the number of repeating units of the homologous series varise successively, they were able to described as the following equations: P=a+bn(1/c),where a、 b、 c all refer to the constants, n to the number of repeating units, p to the physical properties of homologous straight-chain alkanes compounds series. Significant correlation was found between the physical properties of homologous straight-chain alkanes series and their number of repeating units in this models.
Resonance Raman intensities and UV-visible absorption spectrum of nickel(II) porphyrin (NiP) were analyzed with time-dependent formulas under standard approximations for Condon mechanism of enhancement. The resultant dimensionless displacements on S2 state are comparable with those obtained by Spiro et al. from Kramers-Kronig transform methods. It was deduced from the calculations that there are large dimensionless displacements on the excited state along ν8 and ν2 coordinates. These normal modes consist of relatively large components of CβCβ, Cα Cm bond stretching and CαCmCα bond bending motions. Compared with the ground state, the average bond-lengths of CβCβ, CαCm, and CαN bonds at S2 state increase respectively by 0.27, 0.14, and 0.07pm,while that of CαCβ bond decreases by 0.20pm,which are well in coincident with the SPMO calculations in literature.
The principal properties of electronic energy band structure for the chiral single-walled carbon nanotube (SWNTs) were investigated. Methods to decide the subband index crossing or approaching the Fermi level and decided the related wave vector ky are developed. Starting from the  A-B effect, the conditions of metal-semiconductor transition continuously for the chiral SWNTs under inducing by the magnetic field are deduced and the general change pattern of energy gap is discussed in detail.
Nano-Ni/mesoporous SiO2 composites were obtained by reducing Ni2+-doped SiO2 xerogels in H2, which were prepared via a sol-gel route. The average size of nano-Ni particles in mesoporous composites was estimated at 11~12nm from TEM (Transmission Electron Microscope) photographs. The results of magnetic measurements show that compared with the conventional nano-Ni particles, the Ni particles in nano-Ni/mesoporous SiO2 composites remain superparamagnetic state when their particle size is larger than the critical size of Ni calculated theoretically. Elevation of the reduction temperature promotes transformation of nano-Ni particles in mesoporous composites into the superparamagnetic state within a certain range of temperature.
The fabrication of mixed style shielding film filled with carbon nanotubes/ graphite and the influence of their constitution and treat conditions on the conductivity and their ageing properties are presented. Based on experiments, it is found that the shielding films are of the best electronic, shielding and mechanical properties with the ratios of carbon nanotubes to graphite and organic polymer to conductive substance ranging from 1/7 to 1/2 and from 29.6/70.4 to 32.4/67.6 respectively, and in some conditions, they occur negative temperature coefficient. A formula of current density of shielding films can be derived from multiple layers structure model, whose theoretical value agrees with experimental results very well. It was compared between shielded properties of Cu and Ni vapour films and carbon nanotubes/graphite film.
Major phases mullites prepared by hydrothermal crystallization method with kaolinite as raw material, were composite nanocrystals. The matter phases, grain size and thermal stability of composite nanocrystals made in different condition were characterized by XRD, TEM, BET and TG-DTA. Major phases nanocrystals were studied in Temperature Programmed Desorption of CO, SO2, and supported Ni, Co, and Mn were measured in Temperature Programmed Reduction(TPR). The CO2 and solid sulfur were found in adsorption preduts. It was showed that adsorbates have changed on the surface of the nanocrystals. Due to different particle sizes of micro-metre scales crystals and nanocrystals of the supported Ni, Co and Mn, peak temperature and area differed along with the different interaction between supported oxides and the support. It was showed that there was structural effect between the supported oxides of Ni, Co, Mn and the supporter. Moreover, structural difference in the surface of crystals led to different comsumption of H2.
A series asymmetric poly (ether sulfone) gas separation membranes were prepared by dry/wet phase inversion processes. The membrane formation processes include two main processes, the evaporation process was dynamically monitored with FTIR-ATR and the immersion process was dynamically photoed with optical microscope. The kinetic effect of the dry/wet phase inversion process on the morphology has been studied. It is concluded that two factors (convection evaporation and solvent/nonsolvent exchange rate) are important in controlling membrane morphology for gas separation.
For further studied on nano-Ni catalytic hydrogenation of pyroole and its derivatives at normal temperature and pressure, we have did relevant catalytic hydrogenation experiments to pyrrole, pyrrolidine and pyrrolidone. The images and microstructure of nickel-based catalytic, hydrogenation activity and effect of ultrasonic wave were detected by the TEM-HREM and XRD. Besides the products of hydrogenation were investigated by the UV and GC. The results demonstrated that employment of ultrasonic wave has benefit on the maintenance of catalyst activity. The interspace of nickel (111) crystal face increases its distance at 1.5%. The nanosized nickel-based catalyst exhibits catalytic activity for the hydrogenation of pyrrole, pyrrolidine and pyrrolidone at normal temperature and pressure. The hydrogenation of pyrrole produces pyrrolidine at first, then the ring is broken and low-C hydrocarbons, ammonia etc are produced. The general reaction is found to be zero-order, which agrees with the character of surface-contact reaction.
The phenomenon of 17O, 18O enrichment in the surface layer of CdO was investigated by means of temperature-programmed desorption-ion-trap detector (TPD-ITD), quadrupole mass spectrometer(QMS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction(XRD)etc.The results obtained showed that the Cd(OH)2-CdCO3 surface layer of CdO possesses the ability of selective inclusion of oxygen molecules containing 17O, 18O in air.
A new formula for the specific heat jump ΔC|Tc to the phase transition of the second order and generalized Ehrenfest equation are derived by means of the method of endoreversible Carnot cycle, which can mirror the irreversible features in a phase transition of the second order. The results are universal for reversible phase transition and irreversible phase transition of various substances. Then, the irreversible phase transition of the second order for simple system (P,V,T), the superconducting transition and paraelectricity-ferroelectrics transition are discussed by means of the new formula for the specific heat jump.
The confined crystallization of hard segments in butylene terephthalate-ε-caprolactone (PBT-PCL) copolyesters were carefully investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction. Every copolyesters exhibits only one transition temperature Tg. The uncrystallized hard and soft segments form a relatively compatible amorphous phase. For those copolyesters with hard segment content higher than 50%, the hard segments can crystallize, while the soft segments can not. The soft segments confine the crystallization of hard segments. The crystallizability of hard segments increases with increasing hard segment sequence length.