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71.
72.
We studied multiple ionization of single nucleobases by means of slow highly charged ions (Xe(q+), q=5-25). The products of the subsequent fragmentation were studied using high resolution coincidence time-of-flight spectrometry. We observed a strong dependence of the fragment kinetic energies on the initial charge state of the intermediate parent ions as well as on the initial chemical environment of the respective fragment ions within the parent molecule. The data allow us to shed light on the charge distribution within the molecule as well as on the fragmentation dynamics of these intermediate size systems. 相似文献
73.
Vestergaard EK Vang RT Knudsen J Pedersen TM An T Laegsgaard E Stensgaard I Hammer B Besenbacher F 《Physical review letters》2005,95(12):126101
The influence of high pressures of carbon monoxide (CO) on the stability of a Au/Ni(111) surface alloy has been studied by high-pressure scanning tunneling microscopy. We show that CO induces a phase separation of the surface alloy at high pressures, and by means of time-lapsed STM movies we find that Ni atoms are removed from the surface layer during the process. Density functional theory calculations reveal the thermodynamic driving force for the phase separation to be the Au-induced compression of the CO overlayer with a resulting CO-CO repulsion. Furthermore, the atomistic mechanism of the process is shown to be kink-site carbonyl formation and evaporation which is found to be enhanced by the presence of Au. 相似文献
74.
Hadjar O Foldi P Hoekstra R Morgenstern R Schlatholter T 《Physical review letters》2000,84(18):4076-4079
Multiply charged ion-induced fragmentation and ionization of C60 is governed by electronic and nuclear stopping of the projectile as well as charge exchange. We have studied the collision dynamics as a function of the projectile atomic number Z ( 2=Z=18) for constant projectile velocity v at charge states q = 2,3. Strong oscillations of electronic-stopping-related quantities such as ionization and fragmentation are observed. From the properties of the oscillations, we obtain information on the effective electron density of the fullerene. 相似文献
75.
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77.
Torque measurements have been performed at 4 and 77 K on single crystals of Mn1?xFe2+xO4 (0<x<0.05) and MnFe2?xTixO4 (0<x<0.1). The crystals were either quenched or slowly cooled causing a change of inversion by 0.1. It is found that the magnetic anisotropy due to the ferrous ions in the Ti-doped samples is 80 per cent larger than in the Mn1?xFe2+xO4 crystals. In both crystal series the ferrous ion anisotropy in the slowly cooled crystals is 70 per cent higher than in the quenched crystals. The K1 of MnFe2O4 at 4 K is found to decrease from ?3.6 × 105 erg/cm3 after show cooling, down to ?2.6 × 105 erg/cm3 after quenching. 相似文献
78.
The "switchable mirror" yttrium hydride is one of the few strongly correlated systems with a continuous Mott-Hubbard metal-insulator transition. We systematically map out the low temperature electrical transport from deep in the insulator to the quantum critical point using persistent photoconductivity as a drive parameter. Both activated hopping over a Coulomb gap and power-law quantum fluctuations must be included to describe the data. Collapse of the data onto a universal curve within a dynamical scaling framework (with corrections) requires znu=6.0+/-0.5, where nu and z are the static and dynamical critical exponents, respectively. 相似文献
79.
Charge localization in multiple ionization and fragmentation of small argon clusters is reported. The processes are initiated by interaction of the neutral cluster with highly charged Xe(q+) (5< or =q< or =25). Products are detected by means of multicoincidence time-of-flight methods. A strong dependence of the fragmentation pattern on the Xe charge state q is observed. In particular, we find evidence for formation of multiply charged atomic Ar(r+) fragment ions up to r = 7. Such high charge states have neither been observed in fission of multiply charged van der Waals clusters nor in ion-induced fragmentation of fullerenes or metal clusters. This hints at fundamentally different excitation and fragmentation dynamics. 相似文献
80.