Search results for "CONI"
showing 10 items of 984 documents
Focal squeeze in axicons
2005
The on-axis irradiance distribution of a truncated conical wavefront is evaluated in terms of the Fresnel number of the focusing geometry. In agreement with geometrical optics, a focal line of increasing intensity is generated for extremely high Fresnel numbers. Otherwise clear deviations may be observed for the position of the maximum irradiance along the optical axis. A remarkable focal squeeze appears and, for decreasing Fresnel numbers, this effect manifests stronger. An analytical formula is provided for the fast evaluation of the focal squeeze.
Similar chemical structures, dissimilar triplet quantum yields: a CASPT2 model rationalizing the trend of triplet quantum yields in nitroaromatic sys…
2019
The photophysics of nitroaromatics compounds stand out for being characterized by an ultrafast decay into the triplet manifold and by a significant value of the triplet quantum yield. The latter quantity can change dramatically from one system to another, as proven for the molecules 2- nitronaphthalene, 1-nitronaphthalene, and 2methyl-1nitronaphthale, whose triplet quantum yield have been previously measured to be 0.93 ± 0.15, 0.64 ± 0.12, and 0.33 ± 0.05, respectively (J. Phys. Chem. A 2013, 117, 14100). In the present contribution we rationalize the reported trend for the triplet quantum yield on the basis of the different ability that the excited S 1 state has in the three molecules to r…
(2+1)-dimensional Einstein-Kepler problem in the centre-of-mass frame
1999
We formulate and analyze the Hamiltonian dynamics of a pair of massive spinless point particles in (2+1)-dimensional Einstein gravity by anchoring the system to a conical infinity, isometric to the infinity generated by a single massive but possibly spinning particle. The reduced phase space \Gamma_{red} has dimension four and topology R^3 x S^1. \Gamma_{red} is analogous to the phase space of a Newtonian two-body system in the centre-of-mass frame, and we find on \Gamma_{red} a canonical chart that makes this analogue explicit and reduces to the Newtonian chart in the appropriate limit. Prospects for quantization are commented on.
Emission and null coordinates: geometrical properties and physical construction
2011
A Relativistic Positioning System is defined by four clocks (emitters) broadcasting their proper time. Then, every event reached by the signals is naturally labeled by these four times which are the emission coordinates of this event. The coordinate hypersurfaces of the emission coordinates are the future light cones based on the emitter trajectories. For this reason the emission coordinates have been also named null coordinates or light coordinates. Nevertheless, other coordinate systems used in different relativistic contexts have the own right to be named null or light coordinates. Here we analyze when one can say that a coordinate is a null coordinate and when one can say that a coordin…
Transition From Ideal To Viscous Mach Cones In A Partonic Transport Model
2013
Using a partonic transport model we investigate the evolution of conical structures in ultrarelativistic matter. Using two different source terms and varying the transport properties of the matter we study the formation of Mach Cones. Furthermore, in an additional study we extract the two-particle correlations from the numerical calculations and compare them to an analytical approximation. The influence of the viscosity to the shape of Mach Cones and the corresponding two-particle correlations is studied by adjusting the cross section of the medium. peerReviewed
Ion beam coolers in nuclear physics
2003
Cooling techniques for low-energy radioactive ion beams are reviewed together with applications on high-precision measurements of ground state properties of exotic nuclei. The emphasis in the presentation is on cooling, bunching and improving the overall characteristics of ion beams by RFQ-driven buffer gas cooling devices. Application of cooled and bunched beams in collinear laser spectroscopy to extract isotope shifts and hyperfine structure are presented with examples on radioactive Ti, Zr and Hf isotopes. The impact of the new-generation coolers on mass measurements of short-lived nuclei is discussed with examples on precision measurements of masses of super-allowed beta emitters. As a …
Beta Decay of68–74Niand Level Structure of Neutron-Rich Cu Isotopes
1998
The isotopes ${}^{68--74}\mathrm{Ni}$, of interest both for nuclear physics and astrophysics, have been produced in proton-induced fission of ${}^{238}\mathrm{U}$ and ionized in a laser ion guide coupled to an on-line mass separator. Their $\ensuremath{\beta}$ decay was studied by means of $\ensuremath{\beta}$- $\ensuremath{\gamma}$ and $\ensuremath{\gamma}$- $\ensuremath{\gamma}$ spectroscopy. Half-lives have been determined and production cross sections extracted. A partial level scheme is presented for ${}^{73}\mathrm{Cu}$ and additional levels for ${}^{71}\mathrm{Cu}$, providing evidence for a sharply lowered position of the $\ensuremath{\pi}{1f}_{5/2}$ orbital as occupancy of the $\ens…
Jet dynamics and stability
2013
The dynamics and stability of extragalactic jets may be strongly influenced by small (and probable) di_erences in pressure between the jet and the ambient and within the jet itself. The former give rise to expansion and recollimation of the jet. This occurs in the form of conical shocks, or Mach disks, if the pressure di_erence is large enough. Pressure asymmetries within the jet may trigger the development of helical patterns via coupling to kink current-driven instability, or to helical Kelvin-Helmholtz instability, depending on the physical conditions in the jet. I summarize here the evidence collected during the last years on the presence of recollimation shocks and waves in jets. In th…
Hydrodynamical and Emission Simulations of Relativistic Jets: Stability and Generation of Superluminal and Stationary Components
2001
We present 2D hydrodynamical and emission simulations of the jet stabilityafter the introduction of strong perturbations on a relativistic jet. These simulations show that the interaction of a single strong perturbation with the underlying jet results in the formation of multiple conical shocks with very specific observational properties.
Local conical dimensions for measures
2012
AbstractWe study the decay of μ(B(x,r)∩C)/μ(B(x,r)) asr↓ 0 for different kinds of measures μ on ℝnand various conesCaroundx. As an application, we provide sufficient conditions that imply that the local dimensions can be calculated via cones almost everywhere.