Search results for "PLASMA"
showing 10 items of 4043 documents
3d
1999
We have measured the lifetime of the metastable 3D 5/2 level in Ca+ using the “quantum jump" technique on a single stored and laser cooled ion in a linear Paul trap. We found a linear dependence of the measured decay rate on the power of the laser which repumps the ions from the long lived 3D 3/2 level. This can be explained by off-resonant depletion of the 3D 5/2 level. The proper lifetime of this level is obtained by a linear extrapolation of the measured lifetime to zero laser power. We obtain 1100(18) ms in agreement with theoretical calculations. The observed systematic change of the decay rate resolves discrepancies between earlier experiments in which this effect had not been conside…
Femtosecond laser pulse shaping for enhanced ionization
2009
El pdf del artículo es la versión post-print: arXiv:0906.1938v1
VUV diagnostic of electron impact processes in low temperature molecular hydrogen plasma
2015
Novel methods for diagnostics of molecular hydrogen plasma processes, such as ionization, production of high vibrational levels, dissociation of molecules via excitation to singlet and triplet states and production of metastable states, are presented for molecular hydrogen plasmas in corona equilibrium. The methods are based on comparison of rate coefficients of plasma processes and optical emission spectroscopy of lowest singlet and triplet transitions, i.e. Lyman-band ($B^1\Sigma^+_u \rightarrow X^1\Sigma^+_g$) and molecular continuum ($a^3\Sigma^+_g \rightarrow b^3\Sigma^+_u$), of the hydrogen molecule in VUV wavelength range. Comparison of rate coefficients of spin-allowed and/or spin-f…
Gas sensing properties of multiwall carbon nanotubes decorated with rhodium nanoparticles
2011
International audience; In the present work, multiwalled carbon nanotubes were decorated with rhodium nanoparticles using a colloidal solution in the post-discharge of an RF atmospheric plasma of argon (Ar) or argon/oxygen (Ar:O 2). The properties of these hybrid materials towards the room temperature detection of NO 2 , C 2 H 4 , CO, C 6 H 6 and moisture were investigated and discussed in view of compositional and morphological studies. It was found that the presence of oxygen in the plasma treatment is essential to significantly enhance the gas response of Rh-decorated multiwalled carbon nanotubes and to avoid response saturation even at low gas/vapor concentrations. These desirable effec…
Electroplated bismuth absorbers for planar NTD-Ge sensor arrays applied to hard x-ray detection in astrophysics
2018
Single sensors or small arrays of manually assembled neutron transmutation doped germanium (NTD-Ge) based microcalorimeters have been widely used as high energy-resolution detectors from infrared to hard X-rays. Several planar technological processes were developed in the last years aimed at the fabrication of NTD-Ge arrays, specifically designed to produce soft X-ray detectors. One of these processes consists in the fabrication of the absorbers. In order to absorb efficiently hard X-ray photons, the absorber has to be properly designed and a suitable material has to be employed. Bismuth offers interesting properties in terms of absorbing capability, of low heat capacity (needed to obtain h…
Thermal-electrical-mechanical simulation of the nickel densification by Spark Plasma Sintering. Comparison with experiments
2016
Abstract Spark Plasma Sintering is a non-conventional process of the powder metallurgy field which uses a high electrical current to rapidly produce fully dense materials. In the present paper, a thermal-electrical-mechanical model developed on ABAQUS Software is proposed to simulate the densification of a nickel disk. A compaction model, studied in [Wolff, C., Mercier, S., Couque, H., Molinari, A., 2012. Modeling of conventional hot compaction and spark plasma sintering based on modified micromechanical models of porous materials. Mechanics of Materials 49 (0), 72–91. URL http://www.sciencedirect.com/science/article/pii/S0167663611002195 ], has been used to reproduce the densification of t…
Depolarization Field in Thin Ferroelectric Films With Account of Semiconductor Electrodes
2005
Within the framework of the phenomenological Ginzburg-Landau theory influence of semiconductor electrodes on the properties of thin ferroelectric films is considered. The contribution of the semiconductor electrodes with different Debye screening length of carriers is included in the functional of free energy. The influence of highly doped semiconductor electrodes on the depolarization field and the film properties was shown to be great.
Stand-Off Magnetometry with Directional Emission from Sodium Vapors
2021
International audience; Stand-off magnetometry allows measuring magnetic field at a distance, and can be employed in geophysical research, hazardous environment monitoring, and security applications. Stand-off magnetometry based on resonant scattering from atoms or molecules is often limited by the scarce amounts of detected light. The situation would be dramatically improved if the light emitted by excited atoms were to propagate towards the excitation light source in a directional manner. Here, we demonstrate that this is possible by means of mirrorless lasing. In a tabletop experiment, we detect free-precession signals of ground-state sodium spins under the influence of an external magne…
Third-harmonic generation in the skin layer of a hot dense plasma
2003
The third-harmonic generation of a pump wave, resulting from the electron-ion collision frequency dependence on the electric field in the skin layer of a hot dense plasma is investigated. The relation of the current third harmonic with the high-frequency field in the skin layer is established for arbitrary ratios of the electron-ion collision frequency to the field frequency. For arbitrary ratios of these two frequencies, the field structure inside the skin layer is determined, and the field of the wave irradiated by the plasma at tripled frequency, too, is calculated. It has permitted us to find the explicit dependencies of the third-harmonic generation efficiency on the plasma and pump fi…
Ferroelectric plasma source as an exciting source for rare earth elements
2003
The plasma sources basing on electrical discharges near the surfaces of ferroelectric materials have been described. It was shown that the ferroelectric plasma sources are especially useful for investigations in the field of optical spectroscopy. They have been found to be especially useful for exciting the atoms and ions or rare earth elements.