arXiv subjects

G. Carugno

Publications and source records attributed to G. Carugno.

44 records · Page 3Linked to original sources

arXiv2008

Dielectric screening--, multiple scattering--, and quantum indistinguishability effects in the IR emission spectrum of Xe$_2$ excimers in dense Xe gas

We report new measurements of the infrared emission spectrum of Xe$_{2}$ excimers produced by electron impact in dense gas at room temperature. These measurements extend the density range previously explored by a factor of two. We have now reached a pressure $P\approx 3.3 $MPa, corresponding to a gas density $N\approx 8\cdot 10^{26} $m$^{-3}$ in both pure Xe gas and in a Ar--Xe mixture. The analysis of the changes of the spectrum induced by the interaction with the gaseous environment shows how cooperative-- and many-body effects develop with increasing density. We %will also show that quantum effects related to the indistinguishability of identical particles are observed even at such high temperature.

physics.atom-ph↗

arXiv2007

Low- and high-density features of IR luminescence of Xe$_{2}$ excimers produced by electron impact

Electron--impact excitation of Xe atoms in pure Xe gas and in a Xe(10 %)--Ar(90 %) mixture has led to the discovery of infrared (IR) luminescence of Xe$_{2}$ excimers. The investigation of the emission spectrum at low gas density has allowed the identification of the molecular states involved in the transition. When the gas density is increased to values up to 40 times larger than the density of the ideal gas at standard temperature and pressure, the interaction of the excimer with the dense environment produces a strong red--shift of the spectrum that is interpreted in terms of many--body effects.

physics.atom-ph↗

arXiv2007

Infrared emission spectrum and potentials of $0_u^+$ and $0_g^+$ states of Xe$_2$ excimers produced by electron impact

We present an investigation of the Xe$_{2}$ excimer emission spectrum observed in the near infrared range about 7800 cm$^{-1}$ in pure Xe gas and in an Ar (90%) --Xe (10%) mixture and obtained by exciting the gas with energetic electrons. The Franck--Condon simulation of the spectrum shape suggests that emission stems from a bound--free molecular transition never studied before. The states involved are assigned as the bound $(3)0_{u}^{+} $ state with $6p [1/2]_{0}$ atomic limit and the dissociative $(1)0_{g}^{+}$ state with $6s [3/2]_{1}$ limit. Comparison with the spectrum simulated by using theoretical potentials shows that the dissociative one does not reproduce correctly the spectrum features.

physics.atom-ph↗

arXiv2005

Environment influence on the IR fluorescence of Xe$_{2}^{*}$ molecules in electron beam excited Ar--Xe mixture at high density

We report new measurements of the near infrared (NIR) Xe$_2^*$ excimer fluorescence in an electron--beam--excited Ar (90%)--Xe (10 %) mixture at room temperature. Previous measurements up to a density $N\approx 2\times 10^{26}$ m$^{-3}$ discovered a broad excimer fluorescence band at $\approx 7800$ cm$^{-1},$ whose center is red--shifted by increasing $N$ (A. F. Borghesani, G. Bressi, G. Carugno, E. Conti, and D. Iannuzzi, {\em J. Chem. Phys.}, {\bf 115}, 6042 (2001)). The shift has been explained by assuming that the energy of the optical active electron in the molecule is shifted by the density--dependent Fermi shift and by accounting for the solvation effect due to the environment. We have extended the density range up to $N\approx 6\times 10^{26}$ m$^{-3}, $ confirming the previous measurements and extending the validity of the interpretative model. A detailed analysis of the width of the fluorescence band gives a value of 2.85 nm for the size of the investigated excimer state. Such a large value lends credence to the validity of the proposed explanation of the experimental findings.

physics.atom-ph↗

arXiv2004

A novel experimental approach for the detection of the dynamic Casimir effect

The Casimir effect is a well-known macroscopic consequence of quantum vacuum fluctuations, but whereas the static effect (Casimir force) has long been observed experimentally, the dynamic Casimir effect is up to now undetected. From an experimental viewpoint a possible detection would imply the vibration of a mirror at gigahertz frequencies. Mechanical motions at such frequencies turn out to be technically unfeasible. Here we present a different experimental scheme where mechanical motions are avoided, and the results of laboratory tests showing that the scheme is practically feasible. We think that at present this approach gives the only possibility of detecting this phenomenon.

quant-ph↗

arXiv2003

Liquid Argon Ionization Detector for Double Beta Decay Studies

A multisection liquid argon ionization detector was developed by the DBA collaboration to study the double beta- decay of $^{100}$Mo. The experiment was carried out in the Gran Sasso underground laboratory in Italy. The detector design and main characteristics are described. The $ββ(2ν)$ decay of $^{100}$Mo was observed and its half-life measured: $T_{1/2}=[7.2 \pm 0.9(stat) \pm 1.8(syst)] \times 10^{18}$ yr. Limits on the 0$ν$ and 0$νχ^{0}$ modes of the decay were obtained: $T_{1/2}> 8.4(4.9) \times 10^{21}$ yr and $T_{1/2}> 4.1(3.2)\times 10^{20}$ yr at 68% (90%) C.L., respectively. In addition the upper limits on the $^{42}$Ar content and $^{222}$Rn activity in liquid Ar were found to be $4.3 \times 10^{-21}$ g/g and $1.2 \times 10^{-3}$ Bq/kg, respectively.

nucl-ex↗

arXiv2002

Measurement of the Casimir force between parallel metallic surfaces

We report on the measurement of the Casimir force between conducting surfaces in a parallel configuration. The force is exerted between a silicon cantilever coated with chromium and a similar rigid surface and is detected looking at the shifts induced in the cantilever frequency when the latter is approached. The scaling of the force with the distance between the surfaces was tested in the 0.5 - 3.0 $μ$m range, and the related force coefficient was determined at the 15% precision level.

quant-ph↗

arXiv2000

Infrared Fluorescence of Xe2 Molecules in beam-excited Xe Gas at high Pressure

We report experimental results of proton- and electron-beam-induced near-infrared (NIR) fluorescence in high-pressure Xe gas at room temperature. The investigated wavelength band spans the range $0.7 \leqλ\leq 1.8 μ{m}.$ In the previously unexplored range for $λ> 1.05 μ{m}$ we have detected a broad continuum NIR fluorescence at $λ\approx 1.3 μ{m}$ that shifts towards longer wavelengths as pressure is increased up to $1.5 {MPa}.$ We believe that this continuum is produced in a way similar to the VUV continua of noble gas excimers and that the pressure-dependent shift can be explained by the interaction of the outer electron of the excimer with the gas.

physics.plasm-ph↗