Resonance-enhanced multiphoton ionization spectroscopy on the B′2Σ+ and B2Π states of NS

Resonance-enhanced multiphoton ionization （REMPI） spectra of N^32S and N^34S have been recorded in the range of 35700-40200 cm^-1. The radical was generated by a pulsed dc discharge of a mixture of SF6 and N2 under a supersonic free jet condition. All the 16 observed bands of N^32S radicals have been assigned, among which 12 bands belong to three transition progressions （v′=0-4, 0）, （v′=1-4, 1） and （v′=2-4, 2） from the X^2П ground state to the B′^2∑^＋ upper state and the rest correspond to （9, 0）, （10, 0）, （11, 0） and （12, 0） bands of B^2П-X^2П transition, respectively. Analysis of the rotationally resolved spectra yields exhaustive spectroscopic constants of both the X^2П ground state and the B′^2∑^＋ excited state. The electronic transition bands of the isotopic molecule N^34S have been rotationally analyzed for the first time and the rotational constants of the ground and upper states have been determined simultaneously.     

Improved descriptions of collective and non-collective rotations in the superheavy nucleus 256Rf

The superheavy nucleus 2S6Rf, where rotational band and multi-quasiparticle isomer have been observed recently, has been investigated using total Routhian surface calculations and configuration-constrained calculations of potential energy surface, with the inclusion of β6 defor- mation. The experimental moment of inertial is well reproduced, indicating that the alignment is delayed due to the β6 deformation. A K^π = 5- or 8- state could form a two-quasiparticle isomer that is calculated to have higher fission barrier than the ground state.     

Concentration modulation laser spectroscopy of the C2 molecule Swan (d3Πg←a3Πu) system

The rotational structure of the C2 molecule Swan (d3Πg←a3Πu) system (0,1) band has been recorded by optical heterodyne magnetic rotation enhanced concentration modulation laser spectroscopy in the range of 17730～17880 cm-1. The C2 molecule is generated by an electric discharge through a mixture of acetylene and argon gas and a well-resolved spectrum is recorded with an absolute accuracy of 0.007 cm-1. Sensitivity of the method enables us to observe not only the traditionally observed branches of ΔΩ＝0 sub-bands but also some ΔΩ≠0 transitions, providing a slight improvement in the accuracy of some molecular constants of the two states. The theoretical spectra are simulated using the effective Hamiltonian of Brown and Merer and directly fitted to observed spectra; rotational parameters are derived from this fit for the two 3Π states.     

TRANSFORMATION OF STRUCTURE IN POLYACRYLONITRILE FIBRES DURING STABILIZATION

The Lonversion of polyacrylonitrile(PAN)fibre to carbon fibre consists of an oxidative stabili-zation process in which the PAN fibre is heated between 200-300℃ in air to give a thermally co-herent structure.The structural changes of PAN fibres during stabilization have been investigatedusing Fourier Transform Infrared Spectroscopy(FTIR)and Differential Scanning Calorimetry(DSC).An attempt has also been made to follow the conversion of the structure using Ramanspectroscopy as a complementary technique.The FTIR spectra of the fibres subjected to variousdegree of heat treatment show a continuous decrease in nitrile absorption and a simultaneous in-crease in intensity of the C=N and/or C=C bands as the stabilization proceeds.A conversion ra-tio(CR)is defined as the intensity of the C=N and/or C=C bands relative to that of the nitrilegroups.The exotherm present in the DSC experiments was observed to weaken progressively dur-ing the stabilization process.It is confirmed that the original PAN structure is dissipating and thenew ladder polymer is being formed.     

密度泛函理论方法研究稀土-过渡金属化合物的磁性和自旋密度图

Magnetic coupling constants J for the complete structures of rare earth\|transition metal compounds:LGdCu(NO\-3)\-3·Me\-2CO(1,Gd(Ⅲ)Cu(Ⅱ)) and [Ce(C\-4H\-7ON)\-4(H\-2O)\-3][Cr(CN)\-6]·2H\-2O(2, Ce(Ⅲ)Cr(Ⅲ)) have been calculated by the combination of the broken\|symmetry approach with the spin project method under the DFT framework.The J value for 1 is a small number in absolute value -2 4cm -1 for calculation,3 5cm -1 for experimental measurement.The spin density distributions are in detail discussed on the basis of Mulliken population analysis,taking into account the coexistence of spin delocalization and spin polarization mechanisms.For 1,the spin distribution in the ground state may be understood as a result of the competition between two mechanisms:a spin delocalization from Cu(Ⅱ) and a spin polarization of Gd(Ⅲ),and the former is dominant.In the case of 2,both transition metal Cr(Ⅲ) and rare earth Ce(Ⅲ) display a spin polarization effect on the surrounding atoms,where a counteraction of the opposite polarization effects leads a low spin density on the bridging ligand C1N1.In the ground state of 2,the stronger polarization effect of Cr(Ⅲ) even causes the positive spin density on the adjacent bridging atom N1.     

Solvent effects on photophysical properties of copper and zinc porphyrins

The photophysics of Zn（tetraphenylporphyrin,TPP）, Zn（tetra-2,4,6-trimethylphenyl porphyrin, TMP）, Zn （tetra-（o-dichlorophenyl） porphyrin, TPPCI8）, Cu（tetraphenylporphyrin,TPP）, Cu（tetra-2,4,6-trimethyl- phenyl porphyrin,TMP）, and Cu（tetra-（o-dichlorophenyl） porphyrin, TPPCIE, TPPCI8） in several solvents have been investigated on steady state and time-resolved spectroscopy. The Cu（TPPCI8 ） is normal and shows no evidence of CT transition in the visible or near UV regions in nonpolar solvent. However, Cu（TPPCI8）shows a blue shift in the absorption spectrum and intramolecular CT bands at absorption spectra in polar solvent, which shows a fluorescence maximum emission at 650 nm and 8.4 ns lifetime. The reason can be attributed to two points. Firstly, the increase of solvent polarity can enlarge outer reorganisational energy, which is favorable to reduce the activation free energy of charger-transfer transition based on Marcus theory of electron transfer. Moreover, the internal heavy-atom effect on Cu（TPPCIE） is encouraging to stabilize the 2T1 state also, which increases the possibility of population to CT band from 2T1 state. This result is in accord with an earlier estimate of a 10 ns lifetime and CT absorption at 640 nm bands for the CT state of Cu （11） octethylporphyrins. Other possible reasons arousing unusual fluorescence like H-bonding, axial ligands, molecular aggregation are excluded.     

Excited-state dynamics in light-harvesting complex of Rhodobacter sphaeroides

Photodynamics of peripheral antenna complexes,light-harvesting complex (LH2) of Rhodobacter (Rb) Sphaeroides 601,was studied using femtosecond pump-probe technique at different laser wavelengths. The obtained results reveal dramatic dynamical evolutions within B800 and B850 absorption bands of antenna complexes LH2. At excitation wavelength around 835 nm,a sharp photobleaching signal was observed which was assigned to the contribution of the two-exciton state,which was further confirmed by the power dependence measurement. Rate equations with eight-level scheme were used to calculate the population evolution in LH2 and the transient dynamics under femtosecond pulse excitation. The research results prove that not only the transition from ground state to one-exciton state but also that from one-exciton state to two-exciton state contribute to the photodynamics of B850.     

Excited-state dynamics in light-harvesting complex of Rhodobacter sphaeroides

Photodynamics of peripheral antenna complexes, light-harvesting complex （LH2） of Rhodobacter （Rb） Sphaeroides 601, was studied using femtosecond pump-probe technique at different laser wavelengths. The obtained results reveal dramatic dynamical evolutions within B800 and B850 absorption bands of antenna complexes LH2. At excitation wavelength around 835 nm, a sharp photobleaching signal was observed which was assigned to the contribution of the two-exciton state, which was further confirmed by the power dependence measurement. Rate equations with eight-level scheme were used to calculate the population evolution in LH2 and the transient dynamics under femtosecond pulse excitation. The research results prove that not only the transition from ground state to one-exciton state but also that from one-exciton state to two-exciton state contribute to the photodynamics of B850.     

Raman spectra of nitrogen-doped tetrahedral amorphous carbon from first principles

The non-resonant vibrational Raman spectra of nitrogen-doped tetrahedral amorphous carbon have been calculated from first principles, including the generation of a structural model, and the calculation of vibrational frequencies, vibrational eigenmodes and Raman coupling tensors. The calculated Raman spectra are in good agreement with the experimental results. The broad band at around 500 cm^-1 arises from mixed bonds. The T peak originates from the vibrations of sp^3 carbon and the G peak comes from the stretching vibrations of sp^2-type bonding of C=C and C=N. The simulation results indicate the direct contribution of N vibrations to Raman spectra.     

Formation of Ferric Porphyrinoids with Unusual Electronic and Magnetic Properties

1 Results Energy levels of the metal 3d orbitals in iron(Ⅲ) porphyrinoids are controlled by various factors such as the nature and number of axial ligands, electronic and steric effects of peripheral substituents, deformation and core modification of porphyrin ring, hydrogen bonding to the axial ligand, etc. By manipulating these factors, we are now able to prepare various iron(Ⅲ) porphyrinoids withunusual electronic and magnetic properties[1]. Here, we report the formation of such complexes as ⅰ) low-spin bis(tBuNC) complexes of OETArP and DAzP showing the (dxy)2(dxz, dyz)3 ground state[2], all the bis(tBuNC) complexes reported previously exhibit the (dxz, dyz)4(dxy)1 ground state, ⅱ) low-spin bis(HIm) complex of TPrC showing the (dxz, dyz)4(dxy)1 ground state; bis(HIm) complexes almost always adopt the (dxy)2(dxz, dyz)3 ground state[3] Ⅲ) one electron oxidation product of iron(Ⅲ) porphyrinate that shows S=0 electronic ground state, one electron oxidized products exhibit either iron(Ⅳ)(S=1) or iron(Ⅲ)(S=5/2 or S=1/2) radical cation(S=1/2). The spectroscopic data of these complexes are quite useful for further developing the material with unique properties(See Fig.1).     

The Microscopic Approach of sdglBM-1 and Its Application to Nucleus ^154Gd

Based on the Dyson expansion theory, a micro-scopic approach of sdglBM-1 is presented and applied to nucleus is, Gd in this paper. The energy spectra and E2 transition have been calculated. Good agreement is obtained in comparison with experimental results.     

Temperature-induced dissociation reaction and dynamics of light-harvesting complex Ⅱ isolated from purple photosynthetic bacterium Rps. palustris

Steady-state absorption spectroscopy, circular dichroism, and resonance Raman spectroscopy have been used to investigate the thermal stability of LH2 complex isolated from purple photosynthetic bacterium Rps. palustris. The results show that： 1） upon increasing the temperature, a transition from B800 and B850 to free bacteriochlorophyll （B780） happens; 2） a gradual decrease and disappearance of CD signal in visible region occur; 3） a shift of the frequency, belonging to C=C and C-C stretching vibration, to higher wavenumber takes place. It is suggested that LH2 complex can be dissociated in the presence of B800, B850 and carotenoids simultaneously. Single-exponential fitting on the dynamic decay curves gives the apparent time constants of hundreds of minutes for various pigments.     

Theoretical study of partial oxidation of ethylene by vanadium trioxide cluster cation

Density functional theory （DFT） study of reaction between vanadium trioxide cluster cation （VO3^＋） and ethylene （C2H4） to yield VO2^＋ ＋ CH3CHO （acetaldehyde） and VO2CH2^＋ ＋ HCHO （formaldehyde） is carried out. Structures of all reactants, products, intermediates, and transition state in the reaction have been optimized and characterized. The results show unexpected barriers in the reaction due to the existence of a η^2-O2 moiety in the ground state structure of VO3^＋. The initial reaction steps combining ethylene adsorption, C=C activation and O-O cleavage are proposed as rate limiting processes. Comparison of reactions of VO3^＋ ＋ C2H4 with VO3 ＋ C2H4 and VO2^＋ ＋ C2H4 in the previous studies is made in detail. The results of this work may shed light on the understanding of C=C bond cleavage in related heterogeneous catalysis.     

Design and Synthesis of Ti-ZrO2 Functionally Graded Materials

Functionally graded materials (FGMs) based on titanium-zirconia system have been prepared by powder metallurgical method. The graded interlayer number and the compositional distribution have been designed by elastic finite element method. The interfacial microstructure between layers, the combining state of phases between Ti and ZrO₂ have been investigated by means of XRD (X-ray diffraction), SEM (scanning electron microscope), EDS (energy dispersive spectrometer) and so on. The co-existing region of Ti and ZrO₂ has been determined by thermodynamic calculation to control the sintering atmosphere. The experimental results show that the joint between Ti and ZrO₂ phases is physical in this composite and ZrO₂ mainly exists as tetragonal phase. The microstructure of Ti-ZrO₂ system FGM exhibits a transition from a zirconia particle dispersion in a titanium matrix to an inverse dispersion of titanium in zirconia. The gradient structure of titanium and zirconia can relieve thermal stress.     

Is there any amphidromic point of S_2 constituent around the Natuna Islands in the southern South China Sea?

The discrepancies that if there is any amphidromic point of S2 constituent and its location if there is around the Natuna Islands in the southern South China Sea have suspended for a long time, however, there is always no convincing research to settle them up to now. The TOPEX/Poseidon and Jason-1 altimeters have been providing a long-term sea surface height data, which can be used to calculate the constants of tidal constituents along the satellite footprint with the harmonic analysis method. Based on more than 12 years altimetry data from T/P and Jason-1, the character of phase lags from harmonic analysis is used to identify if there is a S2 am-phidromic point around the Natuna Islands. The result shows that there is no S2 amphidromic point instead of a nodal line of a standing wave, and the amplitude of S2 constituent is close to zero along the nodal line.     

Decompression-induced disorder to order phase transition in low-melting ionic liquid [OMIM][PF6]

In situ pressure-induced Raman spectral changes of 1-octyl-3-methyl imidazolium hexafluorophosphate （[OMIM][PF6]） have been investigated under the pressure up to 5.86 GPa at room temperature. The results indicated that [OMIM][PF6] experienced a phase transition at about 4.12 GPa during compression, and it was thought as a phase transition of liquid to a superpressurized glass. Upon decompression, from the obvious change of Raman spectra of [OMIM][PF6] at about 0.48 GPa, it could be inferred that a decompression-induced disorder to order phase transition in [OMIM][PF6] occurred. The phase behavior of [OMIM] [PF6] at low temperature under atmospheric pressure was also investigated in detail. The result showed that Raman spectra of [OMIM][PF6] varied slightly and no crystallization occurred upon cooling. These facts suggested that a disorder to order phase transition was induced by decompression in [OMIM][PF6], and [OMIM][PF6] served as a superpressurized glass under the pressure above 4.12 GPa, which was similar to the glassy state at low temperature.     

A first-principles study of displacive β to ω transition in Ti-V alloys

The ground state properties of β and ω phases in Ti-(0–30 at%)V alloys were calculated, and subsequently thermodynamics and energy barriers of the displacive β to ω transition were investigated by first-principles. The results show that the lattice parameters of β and ω phases decreases with increasing V content in Ti-V alloys. The principal lattice strains for the β to ω transition are highly compositional dependent, and the volume variation decreases with increasing V content. The mechanical stability of the ω phase increases initially at the V content around 10 at% and then decreases with increasing V content. Based on the quasiharmonic Debye model, a metastable diffusionless phase diagram has been established, showing that the ω phase is thermodynamically more stable than the β phase at room temperature, anticipating a spontaneous transition from β to ω phases in Ti-V alloys. The calculations of energy pathways indicate that there is an energy barrier during the displacive βto ω transition in Ti-V alloys at temperatures from 100 to 500 K, but not at 0 K.     

A theoretical study of the proton transfer process in the spin-forbidden reaction 1~HNO(1~A') OH~-→3~NO~-(3~Σ~-) H_2O

The spin-forbidden reaction 1HNO(1A') OH-→3NO-(3Σ-) H2O has been extensively explored using various CASSCF active spaces with MP2 corrections in several basis sets. Natural bond orbital (NBO) analysis, together with the NBO energetic (deletion) analysis, indicates that the two isomers have nearly equal total energy and could compete with each other in the title reaction. More significantly, the singlet/triplet surface crossing regions have been examined and the spinorbit coupling (SOC) and energetics have been computed. The computational results indicate that the SOC is very large at the crossing point T1/S0 trans (ca.40.9 cm-1). Moreover, the T1/S0 trans has a low energy of 10.67 kcal/mol relative to that of trans-S0. Therefore, the surface crossing to the triplet state seems much more efficient at the T1/S0 trans region along the minimum energy path (MEP), However, The values of single (P1ISC) and double (P2ISC) passes estimated at T1/S0 trans show that the ISC occurs with a little probability.     

Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ> , namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.     

Influence of magnetic current on the ground state entanglement in an isotropic transverse XY chain

We study the ground state entanglement in a three-qubit XY chain under the influence of a magnetization current. It is found that the ground state changes from a W state to a disentangled state as the magnetic field varies. When the Lagrange multiplier λ> , namely under a strong magnetic current, the ground state holds onto a W state for a large range of the magnetic field strength. A phase transition to the magnetization-current phase occurs under a certain condition.