The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations.
ABSTRACT:The structures of various compositions of nanoalloy clusters Cu x Au y (x ϩ y Յ 30) were determined using the recently developed molecular genetic algorithm. For compositions up to 18 atoms the algorithm found the global minima in all five runs. For clusters with less than 12 atoms, pure Au clusters are most stable. As the total number of atoms increases, clusters with one, two, three, or four Cu atoms become most stable. It has been observed for larger clusters that there is a tendency for structures based on Cu cores surrounded by Au atoms. The calculated second differences in binding energies are in fair agreement with experimental mass spectra for some nuclearities. Finally, the extrapolated cohesive energies for nanoalloys ((Cu 3 Au) m , (CuAu 3 ) m , and (CuAu) m ) gave an average relative error of 11%, compared with the bulk alloys, whereas for the nanoclusters (Au N and Cu N ) the error was less than 6%.
A collisional radiative model for the buffer gas in a DC magnetron discharge has been developed. The model was constructed for argon and was made self-consistent with the electron energy distribution function (EEOF) by solving the time-dependent Boltzmann equation. The evaluation of the importance of stepwise excitation and the role of 4s states as intermediate levels has been studied, as well as the role of radiative cascades from high lying excited states. The influence of the sputtered material on the EEDF and on electron collision rates has been included in the model. Molybdenum was chosen as a representative example of sputtered material. In the second pari of this double paper we use the results of this model calculation to analyse experimental spectroscopic data obtained from oc magnetron sputtering of molybdenum in argon
The structures and stabilities of water clusters (H2O)n with 11⩽n⩽13 are determined by a genetic algorithm approach with two new evolutionary operators—namely annihilator and history operators. These studies show that the modified genetic algorithm provides an efficient procedure for calculating global minima with an especial attention to molecular water clusters. The actual results are in quantitative agreement with previous calculations using the basin hopping Monte Carlo method.
In this combined theoretical and experimental study we report a full analysis of the resonant inelastic X-ray scattering (RIXS) spectra of HO, DO and HDO. We demonstrate that electronically-elastic RIXS has an inherent capability to map the potential energy surface and to perform vibrational analysis of the electronic ground state in multimode systems. We show that the control and selection of vibrational excitation can be performed by tuning the X-ray frequency across core-excited molecular bands and that this is clearly reflected in the RIXS spectra. Using high level ab initio electronic structure and quantum nuclear wave packet calculations together with high resolution RIXS measurements, we discuss in detail the mode coupling, mode localization and anharmonicity in the studied systems.
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