Search results for "Ground"
showing 10 items of 2432 documents
Measurement of the gj factor of hydrogenic ions: a sensitive test of bound state QED
1996
Thegj factor measurement of hydrogenic ions in the 1s ground state is with an expected accuracy of 10−7 a sensitive test of bound state QED. We expect to determine the deviations from the free electron value, caused by relativistic and radiative corrections, up to the orderα/4π(Zα)2 with an accuracy of 1%. As a first step, light ions like C5+ will be investigated. Later on, heavier hydrogenic ions up to U91+ will be examined using the accelerator facilities at GSI in Darmstadt.
Polarization and angular distribution of the radiation emitted in laser-assisted recombination
2007
The effect of an intense external linear polarized radiation field on the angular distributions and polarization states of the photons emitted during the radiative recombination is investigated. It is predicted, on symmetry grounds, and corroborated by numerical calculations of approximate recombination rates, that emission of elliptically polarized photons occurs when the momentum of the electron beam is not aligned to the direction of the oscillating field. Moreover, strong modifications to the angular distributions of the emitted photons are induced by the external radiation field.
Optical super-resolution sensing of a trapped ion's wave packet size
2021
We demonstrate super-resolution optical sensing of the size of the wave packet of a single trapped ion. Our method extends the well known ground state depletion (GSD) technique to the coherent regime. Here, we use a hollow beam to strongly saturate a coherently driven dipole-forbidden transition around a sub-diffraction limited area at its center and observe state dependent fluorescence. By spatially scanning this laser beam over a single trapped $^{40}\mathrm{Ca}^+$ ion, we are able to measure the wave packet sizes of cooled ions. Using a depletion beam waist of $4.2(1)\,\mu$m we reach a spatial resolution which allows us to determine a wave packet size of $39(9)\,$nm for a near ground sta…
Critical behavior in quantum spin chains with composite spin
1989
Composite spin models are constructed such that, by varying two parameters, they interpolate between the spin-(1/2 antiferromagnetic Heisenberg chain and a number of spin-1 models. These include the usual Heisenberg model, the integrable spin-1 model, and the model with an exact valence-bond ground state. Finite-chain calculations are performed on the composite spin model to study its criticality, and to find if the integrable spin-1 model is a multicritical point with a finite gap generated away from it. We find indications for an extended gapless region.
Magicity of theN68iSemidouble-Closed-Shell Nucleus Probed by Gamow-Teller Decay of the Odd-ANeighbors
1999
The particle-hole excitations through the $N\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}40$ subshell around ${}^{68}\mathrm{Ni}$ have been studied by the $\ensuremath{\beta}$ decay of ${}^{69}\mathrm{Co}$ and ${}^{69}\mathrm{Ni}$. The half-life of ${}^{69}\mathrm{Co}$ was measured to be 0.22(2) s, and a new $\ensuremath{\beta}$-decaying isomer with a half-life of 3.5(5) s was identified in ${}^{69}\mathrm{Ni}$. From the decay of the ${}^{69}\mathrm{Ni}$ isomer a 9(4)% mixing of the $\ensuremath{\pi}{p}_{3/2}^{+1}\ensuremath{\nu}{p}_{1/2}^{\ensuremath{-}2}\ensuremath{\nu}{g}_{9/2}^{+2}$ configuration into the ground state of ${}^{69}\mathrm{Cu}$ can be deduced. Significant polarizatio…
Full configuration interaction calculation of Be3.
2004
The full configuration interaction (FCI) study of the ground state of the neutral beryllium trimer has been performed using an atomic natural orbitals [3s2p1d] basis set. Both triangular and linear structures have been considered for the Be(3) cluster. The optimal geometry for the equilateral triangle has been calculated. The potential energy cut sections along the normal a(1)(') mode and one of the components of the e(') mode have then been studied. The FCI symmetric atomization potential of the linear cluster is also reported. It shows a secondary van der Waals minimum at a long bond distance. All singular points in the potential energy curves are characterized. Other properties, like dis…
Precision Laser Spectroscopy of the Ground State Hyperfine Splitting of HydrogenlikeBi82+209
1994
The first direct observation of a hyperfine splitting in the optical regime is reported. The wavelength of the $M1$ transition between the $F=4$ and $F=5$ hyperfine levels of the ground state of hydrogenlike $^{209}\mathrm{Bi}^{82+}$ was measured to be ${\ensuremath{\lambda}}_{0}=243.87(4)$ nm by detection of laser induced fluorescence at the heavy-ion storage ring ESR at GSI. In addition, the lifetime of the laser excited $F=5$ sublevel was determined to be ${\ensuremath{\tau}}_{0}=0.351(16)$ ms. The method can be applied to a number of other nuclei and should allow a novel test of QED corrections in the previously unexplored combination of strong magnetic and electric fields in highly cha…
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…
Interpreting deviations between AR-VTG and GR
2019
The cosmic microwave background (CMB) anisotropies predicted by two cosmological models are compared, one of them is the standard model of general relativity with cold dark matter and cosmological constant, whereas the second model is based on a consistent vector-tensor theory of gravitation explaining solar system and cosmological observations. It is proved that the resulting differences — between the anisotropies of both models — are due to the so-called late integrated Sachs–Wolfe effect and, consequently, cross-correlations between maps of CMB temperatures and tracers of the dark matter distribution could be used in future to select one of the above models. The role of reionization is …
The Random-Phase Approximation
2007
In this chapter we extend the TDA particle-hole formalism of Chap. 9 to include correlations in the nuclear ground state. This sophisticated particle-hole formalism is called the random-phase approximation (RPA). In this description the simple Hartree-Fock particle-hole vacuum is replaced by a correlated ground state involving many-particle-many-hole excitations of the simple particle-hole vacuum. The resulting configuration mixing in excited states is more involved in the RPA than it is in the TDA. The ground-state correlations induce both particle-hole and hole-particle components in the RPA wave function.