Search results for "ionic"
showing 10 items of 2016 documents
Free fermion antibunching in a degenerate atomic Fermi gas released from an optical lattice
2006
Noise in a quantum system is fundamentally governed by the statistics and the many-body state of the underlying particles. Whereas for bosonic particles the correlated noise observed for e.g. photons or bosonic neutral atoms can still be explained within a classical field description with fluctuating phases, the anticorrelations in the detection of fermionic particles have no classical analogue. The observation of such fermionic antibunching is so far scarce and has been confined to electrons and neutrons. Here we report on the first direct observation of antibunching of neutral fermionic atoms. Through an analysis of the atomic shot noise in a set of standard absorption images, of a gas of…
Optical response and shapes of charged sodium clusters; an analogue of the nuclear giant dipole response
1995
Collective vibrations of de-localized electrons against the positive charged ionic background in sodium clusters (plasmon resonances) and the collective vibrations of protons against neutrons in nuclei (giant dipole resonances) have several features in common. However, fundamental differences exist due to differences in the two media; the nucleus is a quantum liquid whereas the metallic medium is more like a plasma with classical positive ions and quantized electrons. The similarities and differences are illustrated by results from optical response measurements for charged sodium clusters with 14 to 48 atoms.
The screened cluster equation of state for hydrogen-helium mixtures: Atomic, molecular, and ionic contributions from first principles
2018
International audience
Exceptional points in a non-Hermitian extension of the Jaynes-Cummings Hamiltonian
2016
We consider a generalization of the non-Hermitian \({\mathcal PT}\) symmetric Jaynes-Cummings Hamiltonian, recently introduced for studying optical phenomena with time-dependent physical parameters, that includes environment-induced decay. In particular, we investigate the interaction of a two-level fermionic system (such as a two-level atom) with a single bosonic field mode in a cavity. The states of the two-level system are allowed to decay because of the interaction with the environment, and this is included phenomenologically in our non-Hermitian Hamiltonian by introducing complex energies for the fermion system. We focus our attention on the occurrence of exceptional points in the spec…
Internal conversion from excited electronic states of 229Th ions
2017
The process of internal conversion from excited electronic states is investigated theoretically for the case of the vacuum-ultraviolet nuclear transition of 229Th. Due to the very low transition energy, the 229Th nucleus offers the unique possibility to open the otherwise forbidden internal conversion nuclear decay channel for thorium ions via optical laser excitation of the electronic shell. We show that this feature can be exploited to investigate the isomeric state properties via observation of internal conversion from excited electronic configurations of Th+ and Th2+ ions. A possible experimental realization of the proposed scenario at the nuclear laser spectroscopy facility IGISOL in J…
Incompatibility in Multi-Parameter Quantum Metrology with Fermionic Gaussian States
2019
In this article we derive a closed form expression for the incompatibility condition in multi-parameter quantum metrology when the reference states are Fermionic Gaussian states. Together with the quantum Fisher information, the knowledge of the compatibility condition provides a way of designing optimal measurement strategies for multi-parameter quantum estimation. Applications range from quantum metrology with thermal states to non-equilibrium steady states with Fermionic and spin systems.
Line Identification of Atomic and Ionic Spectra of Holmium in the Near-UV. Part I. Spectrum of Ho i
2017
The Fourier Transform spectra of a Holmium hollow cathode discharge lamp have been investigated in the UV spectral range from 25,000 up to 31,530 cm−1 (317 to 400 nm). Two Ho spectra have been measured with neon and argon as buffer gases. Based on the intensity ratios from these two spectra, a distinction was made between atomic and ionic lines (ionic lines are discussed in an accompanying paper). Using the known Ho i energy levels, 71 lines could be classified as transitions of atomic Ho, 34 of which have not been published previously. Another 32 lines, which could not be classified, are listed in the literature and assigned as atomic Ho. An additional 370 spectral lines have been assigned…
Vibrational Excitation Hindering an Ion-Molecule Reaction: The c−C3H2+−H2 Collision Complex
2020
Experiments within a cryogenic 22-pole ion trap have revealed an interesting reaction dynamic phenomenon, where rovibrational excitation of an ionic molecule slows down a reaction with a neutral partner. This is demonstrated for the low-temperature hydrogen abstraction reaction $\mathrm{c}\text{\ensuremath{-}}{\mathrm{C}}_{3}{{\mathrm{H}}_{2}}^{+}+{\mathrm{H}}_{2}$, where excitation of the ion into the ${\ensuremath{\nu}}_{7}$ antisymmetric C-H stretching mode decreased the reaction rate coefficient toward the products $\mathrm{c}\text{\ensuremath{-}}{\mathrm{C}}_{3}{{\mathrm{H}}_{3}}^{+}+\mathrm{H}$. Supported by high-level quantum-chemical calculations, this observation is explained by th…
On the Physical Propagators of QED
1993
The true variables in QED are the transverse photon components and Dirac's physical electron, constructed out of the fermionic field and the longitudinal components of the photon. We calculate the propagators in terms of these variables to one loop and demonstrate their gauge invariance. The physical electron propagator is shown not to suffer from infrared divergences in any gauge. In general, all physical Green's functions are gauge invariant and infrared-finite.
SHIFT AND WIDTH OF HeII LINES
1998
Abstract Based on a quantum statistical many-particle theory, the shift and the width of some He II lines have been evaluated. Ion dynamics have been treated within the model microfield method. Furthermore, fine structure splitting has been taken into account in order to check whether this effect is the cause for the existing large discrepancies between theoretical and experimental line widths. Besides the electronic contributions to the line shift, the shift due to the inhomogeneities of the ionic microfield as well as that due to the quadratic Stark effect has been included.