Search results for "ground"
showing 10 items of 2432 documents
Alpha-particle transfer from 6Li to 28Si leading to high excitation of 32S
2006
The excitation of 32S to energies from 24 to 37 MeV followed by its decay to 28Si has been brought about by the two-step alpha transfer reaction 28Si(6Li,d)32S*→α+28Si. A sudden perishing of the decay to the 28Si ground state occurs at 31 MeV of excitation. At about the same energy an increase in the decay to the first excited 2+ state is observed. The yields of 28Si in its ground state or excited to the 21+ and 41+ state prohibit strong fluctuations. This supports the assumption of the existence of states at high excitation in 32S. The results are based on d–α coincidences, which were found to exhibit a strong forward–backward correlation.
Experimental Evidence for Shape Coexistence in 97Sr59 and Implications for the Structure of the Odd-Odd Isotone 98Y
1988
Experimental evidence for shape coexistence in the odd-mass N=59 isotone 97Sr is presented. The ground state and the lowest excited levels of 97Sr are shown to be spherical, whereas a rotational band based on a state at 585 keV has been identified. Three further levels of deformed origin are proposed. Nilsson-orbital assignments are supported by RPA shell-model calculations. These findings lead to a better understanding of the structure of the odd-odd N=59 isotone 98Y.
Spectroscopic data, spin-orbit functions, and revised analysis of strong perturbative interactions for theA 1Σ+andb 3Πstates of RbCs
2010
The current interest in producing ultracold RbCs molecules by optical excitation from weakly bound Feshbach resonances and stimulated decay to the absolute ground state requires detailed analyses of the intermediate excited states. In this study, we present two sets of experimental Fourier-transform spectroscopic data of the $A{ }^{1}{\ensuremath{\Sigma}}^{+}$-$b{ }^{3}\ensuremath{\Pi}$ complex. The $A$-$b$ mixed vibrational levels are the most likely candidates to be intermediates in the molecular formation. The more recent and more accurate data set is from mixed $A$-$b\ensuremath{\rightarrow}X$ transitions, while the second is derived in large part from $(4){ }^{1}{\ensuremath{\Sigma}}^{…
Background independent quantum field theory and gravitating vacuum fluctuations
2019
The scale dependent effective average action for quantum gravity complies with the fundamental principle of Background Independence. Ultimately the background metric it formally depends on is selected self-consistently by means of a suitable generalization of Einstein's equation. Self-consistent backround spacetimes are scale dependent, and therefore "going on-shell" at the points along a given renormalization group (RG) trajectory requires understanding two types of scale dependencies: the (familiar) direct one carried by the off-shell action functional, and an indirect one related to the self-consistent background geometry. This paper is devoted to a careful delineation and analysis of ce…
Sensitivity of Th229 nuclear clock transition to variation of the fine-structure constant
2020
Peik and Tamm [Europhys. Lett. 61, 181 (2003)] proposed a nuclear clock based on the isomeric transition between the ground state and the first excited state of thorium-229. This transition was recognized as a potentially sensitive probe of possible temporal variation of the fine-structure constant, $\ensuremath{\alpha}$. The sensitivity to such a variation can be determined from measurements of the mean-square charge radius and quadrupole moment of the different isomers. However, current measurements of the quadrupole moment are yet to achieve an accuracy high enough to resolve nonzero sensitivity. Here we determine this sensitivity using existing measurements of the change in the mean-squ…
Finite difference time domain simulation of soil ionization in grounding systems under lightning surge conditions
2004
This paper proposes a Maxwell’s equations finite difference time domain (FDTD) approach for electromagnetic transients in ground electrodes in order to take into account the non linear effects due to soil ionization. A time variable soil resistivity method is used in order to simulate the soil breakdown, without the formulation of an initial hypothesis about the geometrical shape of the ionized zone around the electrodes. The model has been validated by comparing the computed results with available data found in technical literature referred to concentrated earths. Some application examples referred to complex grounding systems are reported to show the computational capability of the propos…
Control of Localization and Suppression of Tunneling by Adiabatic Passage
2004
We show that a field of frequency $\ensuremath{\omega}$ combined with its second harmonic $2\ensuremath{\omega}$ driving a double-well potential allows us to localize the wave packet by adiabatic passage, starting from the delocalized ground state. The relative phase of the fields allows us to choose the well of localization. We can suppress (and restore) the tunneling subsequently by switching on (and off) abruptly the fields at well-defined times. The mechanism relies on the fact that the dynamics is driven to an eigenstate of the Floquet Hamiltonian which is a localized state.
The spiked harmonic oscillatorV(r)=r 2+λr −4 as a challenge to perturbation theory
1991
The standard weak- and strong-coupling perturbation series are interpreted as extreme special cases of expansions obtainable within the framework of Rayleigh-Schroedinger perturbation theory with non-diagonal propagators and unspecified zero-order energies. The formalism of the latter type is then tested by our strongly singular example. It proves suitable for applications in the domain of virtually arbitrary couplings. A few related technicalities and especially the quadruple problem of convergence are also discussed.
Dark Photon Oscillations in Our Inhomogeneous Universe
2020
A dark photon may kinetically mix with the ordinary photon, inducing oscillations with observable imprints on cosmology. Oscillations are resonantly enhanced if the dark photon mass equals the ordinary photon plasma mass, which tracks the free electron number density. Previous studies have assumed a homogeneous Universe; in this Letter, we introduce for the first time an analytic formalism for treating resonant oscillations in the presence of inhomogeneities of the photon plasma mass. We apply our formalism to determine constraints from Cosmic Microwave Background photons oscillating into dark photons, and from heating of the primordial plasma due to dark photon dark matter converting into …
Self-consistency conditions for localized magnetic moments in a free electron gas
1969
The self-consistent conditions for a localized magnetic moment in a metal are studied in the case where the density of states of the host metal is free electron like. A method is outlined which in principle allows to determine self-consistently in the Hartree-Fock approximation the relevant parameters of the magnetic ground state of the system. A numerical example is approximately worked out to show how the theory gives reasonable answers in spite of the crudeness of some of the approximations used.