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[en] The study of muonic atoms has yielded a variety of data on the distribution of the nuclear charge and magnetization and on the quadrupole deformation of nuclei (Devons, 1969; Wu and Wilets, 1969; Engfer et al., 1974); and more recently, on the change in the nuclear charge distribution between different nuclear states (Backe et al., 1974). The latter gives rise to what is usually called the muonic isomer shift, which is the subject of this chapter. The particular role the muon plays in probing the nucleus is primarily due to its mass being 207 times that of an electron. Consequently, the Bohr radii of muonic orbits are smaller by this factor. Actually they are so small that in muonic atoms with heavy nuclei the muon spends most of its time inside the nucleus. Clearly, the binding energy of the muon then depends sensitively on the proton distribution in the nucleus. Analogical to the Moessbauer isomer shift, the muonic isomer shift arises from the monopole term of the electrostatic interaction between the protonic charge distribution and the charge distribution of the leptons bound to the nucleus. (Auth.)
[en] The transverse decoherence of the kicked beam due to amplitude dependent tune shift and the linear and the second order chromaticity are studied. For the kicked beam the closed analytical expression for the beam centroid evolution in subsequent turns is obtained. Analysis of the kicked beam centroid signal on the machine optical characteristics is given.
[en] This paper proposes the principle of SMES capacity determination for power system stable operation. Adopting the energy function method, the mechanism of SMES damping power oscillation in the classical single-machine infinite-bus (SMIB) system is analyzed. The released kinetic energy during disturbance is the original of power system oscillation, which is taken as the principle of SMES capacity determination. Then, the influence of fault type, fault position, and fault clearing time on the SMES capacity determination are discussed. Using MATLAB simulation, the principle of SMES capacity determination is evaluated.
[en] The quantum-statistical-mechanical (QSM) approach to molecular relaxation phenomena is employed to compare radiationless transitions originating from an electronic state characterized by a single minimum and double minima potential surface for a vibronically active, non-totally symmetric mode. The vibronic level dependence of the decay rates for these two cases has been investigated for both small and large energy gap transitions. It is shown that the behaviour of a molecular system is quite different for an initial state possessing a double minima potential surface as compared to the case in which the initial state possesses a single minimum. (Auth.)
[en] Highlights: • We examined the attainment of the Conical Intersection (CI) in Hipoxantine (Hx). • Charge transfer in the molecule is very important in the evolution of S0 and S1. • Aromaticity impairment and push pull systems in Hx are crucial in attaining its CI. • QTAIM offers valuable tools to study the photostability of nucleobases. We analyzed the evolution of the electron density across the S0 and S1 states potential energy curves of hypoxanthine (Hx) using the Quantum Theory of Atoms in Molecules (QTAIM). Examination of QTAIM energies and electronic populations indicates that charge transfer processes are important in the stabilization of the S1 state towards the Conical Intersection (CI) which confers to Hx its photostability. Our results point that the rise of energy of the S0 state approaching the CI is accompanied by a loss of aromaticity of hypoxanthine. Overall, the analyses presented herein give important insights on the photostability of nucleobases.
[en] To study the dynamics resonances of the Cl + HD reaction which was proposed to proceed via abstraction mechanism with no clear resonances, we perform dynamics calculations by the multiconfiguration time-dependent Hartree (MCTDH) method based on recently developed neural-networks potential energy surface (Science 347 (2015), 60). The HD molecule in (GS), (EX1), (EX2), and (EX3) states is used for the reactant. For GS, no distinctive resonance peak is found, while for EX1 two distinctive peaks at kinetics energies of and eV are investigated. These resonance peaks are well consistent with the previous results (Science 347 (2015), 60). Moreover, the present MCTDH calculations predict well-marked resonance peaks at , and eV for EX2 and EX3, which indicates that anticipation of the chemical bond softening model (Science 327 (2010), 1501) is confirmed in this work.
[en] We investigate the influence of low-energy recoils with respect to the electronic excitation of solids generated in atomic collision cascades. It is found that the electronic friction experienced by recoil atoms moving with kinetic energies below 10 eV contributes substantially to the total excitation energy dissipated into electronic degrees of freedom. The collision dynamics, on the other hand, remain virtually unchanged if the friction loss of these particles is switched on or off. This is illustrated by looking at the yield, emission sites and energies of sputtered surface atoms
[en] Highlights: • High resolution L1-L2,3M Coster-Kronig spectra in Ar are obtained by electron impact. • Many features are due to the autoionizing decay of neutral doubly excited states. • Energy analysis of ejected electrons ruled out hypothesis of the state origins. - Abstract: The ejected electron spectra between 25 and 56 eV kinetic energy in Ar have been measured at several electron impact energies. When the incident energy is above the Ar 2s ionization potential the peaks due to the L1-L2,3M1 and L1-L2,3M2,3 Coster-Kronig (CK) transitions are expected to occur in this region of kinetic energy, but we observe a series of other narrow structures that overlap and sometime dominate the spectrum due to the CK transitions. These features have been attributed to the autoionizing decay of inner valence doubly excited states to the Ar + ground state.
[en] A suitable extension of the Mori theory to deal with non-hermitian hamiltonians leads to a rigorous justification of models of 'reduced' kind for radiationless decay phenomena. By using the model of an excited state sequentially coupled to two dissipative quasicontinua it is shown that the generalized theory leads to a reduced model consisting of only two 'virtual' states. The standard Mori approach, on the contrary, would result in a chain of more than two states (probably an infinite number of states). It is shown, furthermore, that the biexponential decay behaviour can rigorously be justified in two different ways. The first model only consists of couplings of intramolecular type. The second model also involves an external thermal bath. The generalized Mori theory, when applied to the second model leads to a non phenomenological justification for the kinetic scheme. It is shown, furthermore, that excitations by strong radiation fields result in a different decay behaviour according to whether the former or the latter scheme is applied. (orig.)
[en] The hole-pairing problem at the dilute limit on low-dimensional bipartite and non-bipartite lattices is studied by means of the generalized Hubbard model, in which on-site (U), nearest-neighbor (V), and assited-hopping (Δt) terms are considered. The problem is [dressed by mapping the original many-body problem onto a tight-binding one in a higher-dimensional space. It is found that there is a small region around Δt/t0 = 0.5, where the pairing of holes is enhanced and non-pairing of electrons exists. Pairing phase diagrams are analyzed for linear, square and triangular lattices, in comparison with those results obtained from the extended Hubbard model. (orig.)