Search results for " atom"
showing 10 items of 1526 documents
The coupling of the X1Σ+and a3Σ+states of the atom pair Na + Cs and modelling cold collisions
2006
The states X1?+ and a3?+ correlated to the ground-state asymptote of Na (3s) and Cs (6s) atoms have been experimentally investigated using high resolution Fourier-transform spectroscopy. The hyperfine splitting of the a3?+ state levels is partially resolved. Transitions to asymptotic vibrational levels of the a3?+ and X1?+ states were recorded simultaneously. The joint evaluation of the data of both the a3?+ and the X1?+ states allows us to determine accurate potential energy curves of both electronic states. Coupled-channels calculations are finally applied for deriving long range dispersion parameters and the exchange contribution of the molecular potentials, yielding a reliable descripti…
Action potentials induce biomagnetic fields in Venus flytrap plants
2020
Upon stimulation, plants elicit electrical signals that can travel within a cellular network analogous to the animal nervous system. It is well-known that in the human brain, voltage changes in certain regions result from concerted electrical activity which, in the form of action potentials (APs), travels within nerve-cell arrays. Electrophysiological techniques like electroencephalography, magnetoencephalography, and magnetic resonance imaging are used to record this activity and to diagnose disorders. In the plant kingdom, two types of electrical signals are observed: all-or-nothing APs of similar amplitudes to those seen in humans and animals, and slow-wave potentials of smaller amplitud…
Epoch Parameterization by Gabor Atom Density in Experimental Epilepsy
2007
An Electrocorticogram (ECoG), during an epilepsy episode can change dramatically from the normal state into a high amplitude low frequency signal and suddenly return to the normal sate. It is possible to identify some stages in the epilepsy seizure, the most representative of them: basal, preictal, ictal and posictal. ECoG are highly non periodical signals, so they are analyze with T-F algorithms, in order to follow up its frequency evolution through the seizure stages. Each seizure stage has different frequency components and they show up at different time. Experimental epilepsy produce by kindling model in rats is used; signals are recorded at cortex level. The ECoG is decompose by means …
Laser driven structured quantum rings
2015
In this work we study harmonic emission from structured quantum rings (SQRs). In SQRs, electrons trapped in two-dimensional structures are further confined by an external potential composed of N scattering centers arranged on a circle. We build a suitable one-dimensional model Hamiltonian describing this class of systems and analytically solve the associated Schödinger equation. We find that the solution can be expressed in terms of Mathieu functions and focus on the specific case of N = 6. By exactly solving the time-dependent Schödinger equation, we then show how the harmonic response to linearly polarized lasers strongly depends on the ring physical parameters. The results illustrate how…
The Cryogenic AntiCoincidence Detector Project for ATHENA+: An Overview Up to the Present Status
2014
ATHENA+ is a space mission proposal for the next ESA L2-L3 slot. One of the focal plane instruments is the X-ray integral field unit (X-IFU) working in the energy range 0.3–10 keV. It is a multi-array based on TES detectors aimed at characterizing faint or diffuse sources (e.g. WHIM or galaxy outskirt). The X-IFU will be able to achieve the required sensitivity if a low background is guaranteed. The studies performed by GEANT4 simulations depict a scenario where the use of an active anticoincidence (AC) is mandatory to reduce the background expected in L2 orbit down to the goal level of 0.005 cts cm $$^{-2}$$ s $$^{-1}$$ keV $$^{-1}$$ . This is possible using a cryogenic anticoincidence (…
First-principles simulations for attosecond photoelectron spectroscopy based on time-dependent density functional theory
2018
We develop a first-principles simulation method for attosecond time-resolved photoelectron spectroscopy. This method enables us to directly simulate the whole experimental processes, including excitation, emission and detection on equal footing. To examine the performance of the method, we use it to compute the reconstruction of attosecond beating by interference of two-photon transitions (RABBITT) experiments of gas-phase Argon. The computed RABBITT photoionization delay is in very good agreement with recent experimental results from [Klünder et al., Phys. Rev. Lett. 106, 143002 (2011)] and [Guénot et al., Phys. Rev. A 85, 053424 (2012)]. This indicates the significance of a fully-consiste…
Nuclear-spin comagnetometer based on a liquid of identical molecules
2018
Atomic comagnetometers are used in searches for anomalous spin-dependent interactions. Magnetic field gradients are one of the major sources of systematic errors in such experiments. Here we describe a comagnetometer based on the nuclear spins within an ensemble of identical molecules. The dependence of the measured spin-precession frequency ratio on the first-order magnetic field gradient is suppressed by over an order of magnitude compared to a comagnetometer based on overlapping ensembles of different molecules. Our single-species comagnetometer is shown to be capable of measuring the hypothetical spin-dependent gravitational energy of nuclei at the $10^{-17}$ eV level, comparable to the…
Limit on Lorentz-Invariance- and CPT-Violating Neutron Spin Interactions Using a $^3$He-$^{129}$Xe Comagnetometer
2016
We performed a search for a Lorentz-invariance- and CPT-violating coupling of the $^3$He and $^{129}$Xe nuclear spins to posited background fields. Our experimental approach is to measure the free precession of nuclear spin polarized $^3$He and $^{129}$Xe atoms using SQUID detectors. As the laboratory reference frame rotates with respect to distant stars, we look for a sidereal modulation of the Larmor frequencies of the co-located spin samples. As a result we obtain an upper limit on the equatorial component of the background field $\tilde{b}^n_{\bot}< 8.4 \cdot 10^{-34}$ GeV (68\% C.L.). Furthermore, this technique was modified to search for an electric dipole moment (EDM) of $^{129}$X…
Laser cooling of externally produced Mg ions in a Penning trap for sympathetic cooling of highly charged ions
2012
We have performed laser cooling of Mg ions confined in a Penning trap. The externally produced ions were captured in flight, stored and laser cooled. Laser-induced fluorescence was observed perpendicular to the cooling laser axis. Optical detection down to the single ion level together with electronic detection of the ion oscillations inside the Penning trap have been used to acquire information on the ion storage time, ion number and ion temperature. Evidence for formation of ion crystals has been observed. These investigations are an important prerequisite for sympathetic cooling of simultaneously stored highly-charged ions and precision laser spectroscopy of forbidden transitions in thes…
Theoretical analysis of a realistic atom-chip quantum gate
2006
9 pages, 5 color figures; International audience; We present a detailed, realistic analysis of the implementation of a proposal for a quantum phase gate based on atomic vibrational states, specializing it to neutral rubidium atoms on atom chips. We show how to create a double-well potential with static currents on the atom chips, using for all relevant parameters values that are achieved with present technology. The potential barrier between the two wells can be modified by varying the currents in order to realize a quantum phase gate for qubit states encoded in the atomic external degree of freedom. The gate performance is analyzed through numerical simulations; the operation time is ~10 m…