Search results for "induced [background]"
showing 10 items of 366 documents
The Mainz Cluster Trap
1999
When cluster ions are stored by electromagnetic forces they are available in the gas phase for extended preparations and investigations. Over the last decade a Penning trap (Ion Cyclotron Resonance) apparatus has been constructed and further developed with respect to metal cluster research at the Institute of Physics at Mainz. It allows to capture and accumulate ion bunches injected from an external cluster source and to manipulate the ions’ motion, i.e. select and center the clusters of interest. The interactions that have been investigated include those with inert and chemically reactive gases, photons and electrons. Multiple mass spectrometric steps such as fragment ion selection can be …
Observation of electronic and geometric shell structures of small silver clusters
1999
Singly charged silver clusters Open image in new window in the size range n = 17 to n = 78 have been captured and stored in a Penning trap, size selected and subjected to an electron beam which leads to further ionization as well as dissociation. The resulting abundance spectra of doubly and triply charged clusters show several features: (1) A critical size for the production of doubly charged clusters which can be understood in terms of the decay pathways as previously investigated by collision induced dissociation, (2) an odd-even alternation in the abundance of singly and doubly charged clusters which inverses sign with change of charge state, (3) prominent signals for particular doubly …
Experimental dissociation energies of metal cluster dications and their interpretation in a liquid-drop model with empirical corrections
1999
The dissociation energies of doubly charged silver cluster ions in the size range $9l~nl~25$ are measured by multiple collision induced dissociation. They are compared to the dissociation energies of singly charged clusters. To this end, the latter are used to calculate shell corrections in a macroscopic-microscopic model. Good agreement between the resulting predictions of the dissociation energies of the doubly charged systems and the experimental values is found, which indicates the strong influence of electronic effects on the stability of small silver clusters.
Induced gravity and the attractor dynamics of dark energy/dark matter
2010
Attractor solutions that give dynamical reasons for dark energy to act like the cosmological constant, or behavior close to it, are interesting possibilities to explain cosmic acceleration. Coupling the scalar field to matter or to gravity enlarges the dynamical behavior; we consider both couplings together, which can ameliorate some problems for each individually. Such theories have also been proposed in a Higgs-like fashion to induce gravity and unify dark energy and dark matter origins. We explore restrictions on such theories due to their dynamical behavior compared to observations of the cosmic expansion. Quartic potentials in particular have viable stability properties and asymptotica…
Postpulse molecular alignment measured by a weak field polarization technique
2003
We report a direct nonintrusive observation of alignment and planar delocalization of ${\mathrm{C}\mathrm{O}}_{2}$ after an intense linearly polarized femtosecond laser pulse excitation. The effects are measured by a polarization technique involving a perturbative probe that itself does not induce appreciable alignment. We show that this technique allows one to measure a signal proportional to $⟨{cos}^{2}\ensuremath{\theta}⟩\ensuremath{-}1/3$, with $\ensuremath{\theta}$ the angle between the molecular axis and the laser polarization. Simulations that support this analysis allow one to characterize the experimentally observed alignment and planar delocalization quantitatively.
The unitary conformal field theory behind 2D Asymptotic Safety
2015
Being interested in the compatibility of Asymptotic Safety with Hilbert space positivity (unitarity), we consider a local truncation of the functional RG flow which describes quantum gravity in $d>2$ dimensions and construct its limit of exactly two dimensions. We find that in this limit the flow displays a nontrivial fixed point whose effective average action is a non-local functional of the metric. Its pure gravity sector is shown to correspond to a unitary conformal field theory with positive central charge $c=25$. Representing the fixed point CFT by a Liouville theory in the conformal gauge, we investigate its general properties and their implications for the Asymptotic Safety progra…
Electron and nuclear dynamics of a molecular ion in an intense laser field
2004
The dynamics of a two-dimensional $\mathrm{H}_{2}^{+}$ molecule interacting with a strong laser pulse beyond the usual approximation of fixed nuclei is presented. The motion of the nuclei is studied by using the classical Newton laws while the electron is described with a full quantal treatment. The axis of the molecule, initially not aligned to the laser field, performs a long-period pendular motion around the laser polarization axis. Vibrational degrees of freedom are seen to be excited. The radiation emitted by the oscillating charges presents variations that are synchronous to the pendular motion. The possibility of monitoring the motion of the molecule through the emitted radiation is …
Nuclear symmetry energy and neutron skins derived from pygmy dipole resonances
2007
By exploiting Coulomb dissociation of high-energy radioactive beams of the neutron-rich nuclei $^{129\ensuremath{-}132}\mathrm{Sn}$ and $^{133,134}\mathrm{Sb}$, their dipole-strength distributions have been measured. A sizable fraction of ``pygmy'' dipole strength, energetically located below the giant dipole resonance, is observed in all of these nuclei. A comparison with available pygmy resonance data in stable nuclei ($^{208}\mathrm{Pb}$ and $N=82$ isotones) indicates a trend of strength increasing with the proton-to-neutron asymmetry. On theoretical grounds, employing the RQRPA approach, a one-to-one correlation is found between the pygmy strength and parameters describing the density d…
Summary of the HypHI Phase 0 experiment and future plans with FRS at GSI (FAIR Phase 0)
2016
WOS: 000381331200014
The HypHI Phase 0 experiment
2010
10th International Conference on Hypernuclear and Strange Particle Physics -- SEP 14-18, 2009 -- Tokai, JAPAN