127 research outputs found
Electron and ion transport in dense rare gases
A review of the research on electron and ion transport in dense rare gases is
presented. The investigation of the transport properties of electrons in dense
rare gases aims at understanding the dynamics and energetics of electron states
in a dense medium and at elucidating how changes of the environment influence
their nature and scattering properties. The quantum nature of electrons couples
them to the environment is such a way to produce a density-dependent shift of
their energy that is the key to rationalize the observed phenomena.Comment: manuscript submitted to IEEE_TDE
Electron mobility maximum in dense argon gas at low temperature
We report measurements of excess electron mobility in dense Argon gas at the
two temperatures and 162.30 K, fairly close to the critical one
( K), as a function of the gas density up to 14
atomsnm ( atomsnm). For the first time
a maximum of the zero-field density-normalized mobility has been
observed at the same density where it was detected in liquid Argon under
saturated vapor pressure conditions. The existence of the maximum in
the liquid is commonly attributed to electrons scattering off long-wavelength
collective modes of the fluid, while for the low-density gas a density-modified
kinetic model is valid. The presence of the maximum also in the gas
phase raises therefore the question whether the single scattering picture valid
in the gas is valid even at liquid densities.Comment: 21 pages, 9 figures, accepted for publication in J. Electrostatic
Molecular Dynamics Simulations of the O2- Ion Mobility in Dense Ne Gas at Low Temperature: Influence of the Repulsive Part of the Ion-Neutral Interaction Potential
New Molecular Dynamics simulations have been carried out in order to get an
insight on the physical mechanisms that determine the drift mobility of
negative Oxygen ions in very dense Neon gas in the supercritical phase close to
the critical point. Two ion-neutral interaction potentials have been used that
differ by their repulsive part. We have observed that the potential with a
harder repulsive part gives much better agreement with the experimental data.
The differences with the softer repulsive potential previously used are
discussed. We propose that the behavior of the ion mobility as a function of
the gas density is related to the number of neutral atoms loosely bound in the
first solvation shell around the ion.Comment: submitted to IEEE-TDEI, 6 pages, 9 figure
Inhomogeneous gas model for electron mobility in high density neon gas
Experimental studies of electron mobilities in Neon as a function of the gas
density have persistently shown mobilities up to an order of magnitude smaller
than expected and predicted. A previously ignored mechanism (gas
in--homogeneity which is negligible in the thermal mobilities for He and other
gases) is found to reproduce the observed Neon mobilities accurately and simply
at five temperatures with just one variable parameter. Recognizing that a gas
is not a homogeneous medium, a variation in local density combined with the
quantum multi--scattering theory, shifts the energy and cross section -- which
in turn changes the collision probability and finally the mobilities. A lower
density where a momentum transfer interaction occurs moves the mobility
strongly in the same direction as the anomalous experiments. By going backwards
from the observed mobilities, the collision frequency at each temperature and
density is made to reproduce the experimental data by looking for the local (as
opposed to average) density at which the (rare) momentum transfer interactions
occur. These density deviations give a picture of the size and behavior of the
wave packets for electron motion which looks very much like the often discussed
wave function collapse.Comment: 18 pages, 5 figure
Infrared and visible scintillation of Ho3+-doped YAG and YLF crystals
In our effort to develop a new kind of detector for low-energy, low-rate energy deposition events we have investigated the cathodo- and radioluminescence of Ho:YAG and Ho:YLF single crystals in an extended wavelength range from 200 nm to 2200 nm. The emission spectra of both crystals show a much more intense emission in the infrared range than in the visible one. We estimate an infrared light yield of several tens of photons/keV when exciting the crystals with X-rays of energy 48 30 keV. The main reason of this high value is due to the Ho3+ ions energy levels scheme that allows efficient cross relaxation processes to occur even at low dopant concentration
Generation of microwave radiation by nonlinear interaction of a high-power, high-repetition rate, 1064-nm laser in KTP crystals
We report measurements of microwave (RF) generation in the centimeter band
accomplished by irradiating a nonlinear KTiOPO (KTP) crystal with a
home-made, infrared laser at nm as a result of optical rectification
(OR). The laser delivers pulse trains of duration up to s. Each train
consists of several high-intensity pulses at an adjustable repetition rate of
approximately GHz. The duration of the generated RF pulses is
determined by that of the pulse trains. We have investigated both microwave-
and second harmonic (SHG) generation as a function of the laser intensity and
of the orientation of the laser polarization with respect to the
crystallographic axes of KTP.Comment: 5 pages, 5 figures, to appear in Optics Letters, vol. 38 (2013
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