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Dual-level electronic structure calculation has been performed to investigate the mechanism and all possible channels of OH radical reaction with CH3CH2F. Geometries and frequencies are computed at the B3LYP/6-311G(d,p) level of theory for all stationary points and complexes and transition states are located. Potential energy surfaces are constructed at the PMP2/cc-pVTZ//B3LYP/6-311G(d,p) level + ZPE correction. Four types of reaction channels are identified: hydrogen abstraction, fluorine abstraction and attack on carbon atom along or perpendicular to the C–C bond axis. Hydrogen abstraction channels have lower barriers and are more exothermic, while out-of-plane β–H abstraction with the lowest barrier is competitive with a–H abstraction. Due to the high energy barrier, contributions of non-H abstraction channels are excluded. The influence of hydrogen bonding interaction is clearly observed in the barrier heights.

A new system based on dendritic polyethylene-cationic poly(p-phenylene ethynylene) core-shell nanoparticles was developed for live-cell imaging. By using the combination of molecular-wire and "dendritic effects" strategies, this design provides the new system with higher photoluminescence quantum yields, lower cell viability and better cellular permeability compared with free cationic poly(p-phenylene ethynylene), allowing it to exhibit remarkable improvements in fluorescence imaging for live cells.

A new-generation TMCP(NG-TMCP) with ultra fast cooling(UFC) as core technique was suggested instead of the conventional TMCP in which some problems are to be solved. And the ultra fast cooling technology has been successfully applied to the plate rolling production in Shouqin Metal Materials Co. Ltd. Industrial trials are reported for the production of X70 pipeline steels (about 70000 t) under UFC conditions. Pipeline steels with reasonably good properties have been produced on an industrial scale. UFC can improve the temperature uniformity, the mechanical properties and the plate profile of X70 pipeline steel. The performance features of the trial plates can meet the standard of X70 pipeline steel. Spot test results have shown that the qualification rate of shape control, the performance and charpy impact properties for the trial plates are 95%, 97% and 98%, respectively. The impact values of X70 pipeline steel at UFC mode exceed the standard requirements of X80 pipeline steel. The productivity is enhanced because cutting quantity of head and tail of the plate is reduced. The enhancement of control accuracy of the red back temperatures is favorable for industrial production of X70 pipeline steel. The reduced production of the steel-making has been industrially achieved, since a new composition was designed by reducing the vanadium content to less than 0.045 wt.%.

A carbon-supported PdSn (PdSn/C) catalyst was prepared by a chemical reduction method with the aid of microwave radiation and was characterized by X-ray diffraction spectroscopy and energy dispersive spectroscopy. Formic acid electrooxidations on PdSn/C and Pd/C catalysts were investigated and compared in an acidic medium by voltammetry and chronoamperometry. The results show that the performance of the PdSn/C-3 catalyst which ratio of Pd:Sn is about 3:1 for formic acid oxidation is greatly improved compared with that of Pd/C; thus, PdSn/C-3 is a promising candidate as an anode catalyst in direct formic acid fuel cells. Additionally, the value of the apparent activation energy shows that the activity of formic acid oxidation on the PdSn/C is sensitive to the temperature at relatively high potentials.

The ultrafast dynamics of the s(1) (n pi*) state of pyridine has been investigated by using ferntosecond time-resolved mass spectrometry and photoelectron imaging combined with (1 + 2') resonance-enhanced multiphoton ionization via the rydberg states. upon excitation into the channel-three region, an ultrafast decay process is observed with a lifetime of about 3.7 ps. the fragment ions show an additional ultrafast decay component. time resolved photoelectron imaging experiments reveal the excited pyridine in channel three region relaxes to an optically dark state on this short time scale. according to previous experimental and theoretical results. we suggest tentatively the ultrafast channel is due to ivr induced fast internal conversion. (c) 2009 elsevier b.v. all rights reserved.

The ultrafast dynamics of benzaldehyde upon 260, 271, 284, and 287 nm excitations have been studied by femtosecond pump-probe time-of-flight mass spectrometry. A bi-exponential decay component model was applied to fit the transient profiles of benzaldehyde ions and fragment ions. At the S2 origin, the first decay of the component was attributed to the internal conversion to the high vibrational levels of S1 state. Lifetimes of the first component decreased with increasing vibrational energy, due to the influence of high density of the vibrational levels. The second decay was assigned to the vibrational relaxation of the S1 whose lifetime was about 600 fs. Upon 287 nm excitation, the first decay became ultra-short (56 fs) which was taken for the intersystem cross from S1 to T2, while the second decay component was attributed to the vibrational relaxation. The pump-probe transient of fragment was also studied with the different probe intensity at 284 nm pump.

Photodissociation dynamics of NO(2) in its conical intersection region have been explored experimentally on a real-time scale by time-of-flight mass spectrometry. Excited at 400.6 nm and probed by 801.6 nm femtosecond laser pulses, different dynamical behaviors of both the parent ion NO(2)(+) and the fragment ion NO(+) have been observed under parallel and perpendicular pump-probe laser polarization configurations. Distinct oscillations in NO(2)(+) and NO(+) signals are observed when laser polarizations of pump and probe are perpendicular to each other, whereas the oscillations become blurry when the laser polarizations are parallel. The observed transient signals imply that the dissociation mechanism of NO(2) in the A(2)B(2) excited state needed to be reconsidered. On the basis of our observation, Rydberg states play important roles in the ultrafast dissociation dynamics of NO(2).

The ultrafast dynamics of chlorobenzene clusters upon 271 nm excitation is studied by femtosecond pump–probe time-of-flight mass spectrometry. Transient profiles of clusters are fitted by two-exponential decay component models, an ultrafast component and a slow decay component. The ultrafast (∼170 fs) decay of S 1 state is tentatively attributed to the internal conversion to the high vibrational levels of S 0 state. Lifetimes of this ultrafast component decease with the cluster size, due to the influence of the solvation effects, while lifetimes of the slow decay component (>1 ns) increase with the cluster size, due to the increase of freedom degrees.

The laser-induced alignment effects of NO in linearly polarized femtosecond laser field within the intensity order of 10 14 W/cm 2 at 820 nm have been investigated experimentally by using velocity mapping technique. The angular and velocity distributions of fragment ions with different charge numbers are measured. The alignment degrees increased with the charge numbers, and were nearly independent of the laser intensities. Our results indicate the geometric alignment dominates before the ionization of NO into NO 2+ , while the dynamic alignment of the molecular ions dominates after the ionization.

The titled reactions are theoretically studied at MP4 (SDTQ) level with 6-311++G(3df,3pd) basis set. All the possible reaction channels are considered for the first time. The most favorable reaction path in H2CO + OH is the channel of producing H2O, which is exothermic by −32.02 kcal/mol, in well agreement with reported experimental result. For H2CO + OH−, the most favorable reaction channel is for H2 molecule formation through several paths. The reaction channels for producing H2 molecule in the titled systems are proposed for the first time. H atom formation in H2CO + OH and hydrogen symmetric transition in H2CO + OH− is also evaluated at higher theory level than literatures.

The behavior of benzene produced during the fixed-temperature reaction and the temperature-programmed surface reaction of methane under non-oxidation aromatization over Mo/HZSM-5 catalyst was monitored in real-time by the resonance-enhanced 2-photon ionization technique. A new phenomenon of benzene formation in the induction period is found to correspond to the migration of the molybdenum species in the catalyst.

Although the photodissociation of nitroaromatics in low excitation electronic states has been extensively studied in recent decades, little is known about the highly excited electronic states. The fragmentation dynamics of three nitroaromatics, nitrobenzene, o-nitrotoluene, and m-nitrotoluene, in highly excited states, populated by the absorption of two photons at 271 nm, are studied with time-of-flight mass spectrometry. The temporal evolutions of the highly excited states are monitored by one-photon ionization at 408 nm. The transients of parent and fragment ions exhibit two ultrafast deactivation processes. The first process is ultrafast internal conversion from the initial excitation to Rydberg states in tens of femtoseconds. The second one is conversion from the Rydberg states to the vibrational manifold in the ground electronic states within hundreds of femtoseconds. The internal conversion process is accelerated by methyl substitution. In o-nitrotoluene, the two processes become much faster due to the hydrogen transfer from the CH(3) to the NO(2) group (ortho effect).

We describe here the electron microscopy and mechanical property studies that were conducted in an industrially processed 20- and 40-mm C-Mn thick plates that involved a new approach of ultrafast cooling (UFC) together with significant reduction in Mn-content of the steel by ~0.3 to 0.5 pct, in relation to the conventional C-Mn steels, with the aim of cost-effectiveness. The study demonstrated that nanoscale cementite precipitation occurred during austenite transformation in the matrix of heavy plate during UFC, providing significant precipitation strengthening. With decrease in UFC stop temperature and consequent increase in the degree of undercooling, there was a transition in the morphology of cementite from lamellar to irregular-shaped nanoscale particles in the 20 mm heavy plate. With the increase in plate thickness, nanoscale cementite precipitated in bainitic lath at the surface of 40 mm heavy plate, which significantly increased the strength and decreased the elongation. Simultaneously, microstructural evolution in hot-rolled sheets was studied via simulation experiments using laboratory rolling mill to define the limits of microstructural evolution that can obtained in the UFC process and develop an understanding of the evolved microstructure in terms of process parameters.