We have observed the motion of Sm+ ions as well as Sm atoms produced by femtosecond laser ablation of a solidified samarium solution sample on substrates by
using a planar laser-induced fluorescence method. Kinetic energies of both Sm+ ions and Sm atoms increase as the electrical conductivity of the substrate decreases, which suggests the effect of surface
charging. The kinetic energy of Sm+ ions is larger than that of Sm atoms for a variety of substrates due to the further electrical acceleration by the surface
charge. The knowledge of ion motion will be the key information for the optimization of femtosecond laser simultaneous atomization
and ionization of organic and inorganic samples on substrates. 相似文献
We present a measurement of the branching fraction B(D{s}{+}-->mu{+}nu{mu}) using a 548 fb{-1} data sample collected by the Belle experiment at the KEKB e{+}e{-} collider. The D{s} momentum is determined by reconstruction of the system recoiling against DKgammaX in events of the type e{+}e{-}-->D{s}{*}DKX, D{s}{*}-->D{s}gamma, where X represents additional pions or photons from fragmentation. This full-reconstruction method provides high resolution in the neutrino momentum and thus good background separation, equivalent to that achieved by experiments at the tau-charm factories. We obtain the branching fraction B(D{s}{+}-->mu{+}nu{mu})=[6.44+/-0.76(stat)+/-0.57(syst)]x10{-3}, implying a D{s} decay constant of f{D{s}}=[275+/-16(stat)+/-12(syst)] MeV. 相似文献
We report a study of the processes e+e- -->J/psiD*D[over](*). In J/psiD*D[over]* we observe a significant enhancement in the D*D[over]* invariant mass spectrum, which we interpret as a new charmoniumlike state and denote X(4160). The X(4160) parameters are M=(4156(-20)+25+/-15) MeV/c2 and Gamma=(139(-61)+111+/-21) MeV. We also report a new measurement of the X(3940) mass and width: M=(3942(-6)+7+/-6) MeV/c2 and Gamma=(37(-15)+26+/-8) MeV. The analysis is based on a 693 fb(-1) data sample recorded near the Upsilon(4S) resonance by the Belle detector at the KEKB asymmetric-energy collider. 相似文献
We report a measurement of the exclusive e+ e- -->Lambda+_(c)Lambda-_(c) cross section as a function of center-of-mass energy near the Lambda+_(c)Lambda-_(c) threshold. A clear peak with a significance of 8.2sigma is observed in the Lambda+_(c)Lambda-_(c) invariant mass distribution just above threshold. With an assumption of a resonance origin for the observed peak, a mass and width of M=[4634 (+8)_(-7)(stat)(+5)_(-8)(syst)] MeV/c(2) and Gamma_(tot)=[92 (+40)_(-24)(stat)(+10)_(-21)(syst)] MeV are determined. The analysis is based on a study of events with initial-state-radiation photons in a data sample collected with the Belle detector at the Upsilon(4S) resonance and nearby continuum with an integrated luminosity of 695 fb(-1) at the KEKB asymmetric-energy e+ e- collider. 相似文献
Molecular design and photoelectrochemically responsive functions of several redox‐tunable building blocks toward conjugated assembling were described. The viologen dimers and pyridylpyridinium dimers through π‐conjugated linkers showed multi‐step redox processes which were demonstrated electrochemically and photochemically. The 4,6‐pyrimidinylene and 3,6‐pyridazinylene linkers played an important role as effective mediators between two attached electrons in the two viologens or pyridinium groups. The latter pyridylpyridinium dimers and 3‐pyridylviologen have potential to coordinate various metal ions to give conjugated self‐assemblies. 相似文献
Fluorescence excitation spectra of 2-aminopurine (2AP) incorporated into single-stranded DNA di- and trinucleotides, as well as into single- and double-stranded pentanucleotides, have been measured as a function of temperature from 5 to 65 °C. Spectral shifts have been precisely quantitated through difference spectroscopy and spectral fits. G(2AP)C and C(2AP)G oligonucleotides have relatively blue-shifted excitation spectra (especially the former) compared to the 2AP free base. The position of the excitation peak of 2AP free base is temperature independent, those of (2AP)T, G(2AP)C, C(2AP)G and TT(2AP)TT shift about 0.4 nm to the blue from 5 to 65 °C, though the spectra of the G-C-containing oligomers also change shape. The temperature dependence of the A(2AP)T spectral position is 2.5-times stronger, and just rises to that of the free base at high temperature. On the other hand, the decrease of yield with increasing temperature is smallest for A(2AP)T, even compared to the free base. The dominant effect when A neighbors 2AP appears to be temperature-dependent stacking with accompanying energy transfer, while in G- and C-containing trinucleotides a temperature-independent interaction keeps the 2AP excitation spectrum blue-shifted. The effect of double strand formation appears to be small compared to stacking interactions. These spectra can be useful in identifying base neighbors and structures of 2AP in unknown 2AP-labeled DNA. 相似文献
Enzymatic degradation of polylactic acid is studied experimentally and analytically. Gel permeation chromatography profiles obtained before and after the enzymatic degradation of polylactic acid (PLA) were introduced into the analysis based on a mathematical model. Previously developed techniques were successfully adapted to the analysis of an initial value problem consisting of an endogenous depolymerization model and an initial condition, and an inverse problem to determine the degradation rate for which the solution of the initial value problem also satisfies a final condition. Those problems were solved numerically and numerical results are introduced. Degradabilities of PLA and polyvinyl alcohol are compared.
We synthesized an azobenzene derivative to demonstrate a one-dimensional molecular zipper. The formation and underlying mechanism of the molecular zipper formed by combined hydrogen-bonding and van der Waals interactions between adjacent molecules were investigated on a Au(111) surface using scanning tunneling microscopy and density functional theory calculations. 相似文献
We investigated the coalescence of ultrathin carbon nanotubes (UTCNTs) using the tight-binding molecular dynamics simulation technique. We have found that two UTCNTs having the same or different chirality can coalesce without initially introducing atomic defects to enhance the reaction. The chiral index of the coalesced nanotube was found to be given as a vector sum of the indices of the original nanotubes, which can be explained geometrically in terms of the developments of the nanotubes. The results clearly show that the chirality can be changed through chemical reaction, which might suggest a possibility of chirality control. 相似文献