Claude GUET - Academia.edu (original) (raw)

Papers by Claude GUET

Nuclear Physics A, 1978

Abstract Fission fragment mass and kinetic energy distributions and mass-versus-energy correlatio... more Abstract Fission fragment mass and kinetic energy distributions and mass-versus-energy correlations have been measured for the thermal neutron induced fission of 231 Pa. The global mass distribution and the mass distribution for selected kinetic energy events show fine structure with a mean period of ≈ 2.5 amu. The peak/valley ratio of the mass distribution is 2271 ± 854 compared to 554 ± 31 for 235 U. The dip ΔE K values at symmetric fission for 231 Pa and 235 U are 14.8 ± 4.2 and 20.6 ± 1.1 MeV respectively. The 〈 E K 〉( μ H ) for μ H ≈ 125–135 is flatter than for 235 U.

Nuclear Physics A, 1989

ABSTRACT A coherent mechanism for the excitation of spin-isospin modes in heavy ion reactions is ... more ABSTRACT A coherent mechanism for the excitation of spin-isospin modes in heavy ion reactions is presented and discussed in two kinematic regimes. The spin-isospin response of nuclei in the particle-hole and in the Delta-hole channels is first studied in charge exchange reactions induced by relativistic heavy ions. Recent data on the reaction 12C[12C, 12N(1+; GS)] at 900 and 1100 MeV per nucleon are particularly suited to study these modes and can be well described by the exchange of effective phonons between the projectile and the target; these effective phonons are built up from the summed interactions between the individual nucleons of the colliding ions. This mechanism in the Delta-hole channel is then used to derive an estimate of the cross section for subthreshold pion production in the 12C[12C, 12C(1+; T = 1; 15.11 MeV)] reaction at 95 MeV per nucleon.

Journal of Nuclear Materials, 2009

The Journal of Chemical Physics, 1999

We have measured the static dipole polarizability of Nay−xLix clusters (with y=2, 3, 4, and 8) by... more We have measured the static dipole polarizability of Nay−xLix clusters (with y=2, 3, 4, and 8) by molecular beam deflection technique. For a given size, the polarizability of pure lithium clusters is smaller than the polarizability of pure sodium clusters. For mixed clusters, a smooth decrease in the polarizability is observed as the proportion of lithium atoms increases. For the NaLi molecule, both experimental permanent dipole and average polarizability have been obtained. Experimental results are compared to results of density functional theory and configuration interaction single and double (CISD) ab initio calculations.

Zeitschrift f�r Physik D Atoms, Molecules and Clusters, 1993

ABSTRACT Ground state and excited states properties of alkali-metal clusters are investigated wit... more ABSTRACT Ground state and excited states properties of alkali-metal clusters are investigated within the framework of the jellium model from the standpoint of the Hartree-Fock theory. The present study deals with closed-shell systems with up to 138 delocalized electrons. Dipoles excited states are described within the random-phase approximation (RPA) with full exchange contributions. The total jellium energy is calculated to second order of many-body perturbation theory with exchange contributions being taken into account fully. The correction to the self-energy that is due to the screening of the Coulomb interaction is evaluated by summing polarization diagrams to all orders. The model is used to calculate the ionization potentials of one-valence-electron systems (9, 21, 41). Results are discussed and compared with others which are based on the local-density-approximation.

Computational Materials Science, 2006

A new approach to the resonance photoabsorption of metal clusters in strong laser fields is intro... more A new approach to the resonance photoabsorption of metal clusters in strong laser fields is introduced. The method is based on the separation of the center of mass and the intrinsic motion of delocalized valence electrons. We calculate the excitation spectra of sodium clusters beyond the standard linear response theory, including highly excited states with more than one plasmon. We study the non-linear effects in photoabsorption of small sodium cluster in strong laser field. The degree of anharmonicity of dipole plasmon excitations is examined.We analyze the ionization of sodium clusters by intense laser pulse with photon energy close to the surface plasmon resonance. The proposed model describes the resonance channel of cluster ionization via excitation of double-plasmon collective electron state that subsequently decays by a single electron emission. The autoionization decay rate of two-plasmon excited state together with the energy and angular distributions of outgoing electrons is obtained for positively charged sodium clusters. Parameters of the laser pulse which are favorable for the resonant multi-plasmon ionization are analyzed.

Physical Review E, 2008

We present the deformation pathway of critically charged glycol and water droplets from the onset... more We present the deformation pathway of critically charged glycol and water droplets from the onset of the Rayleigh instability and compare it to numerical results, obtained for perfectly conducting inviscid droplets. In this simple model presented here, the time evolution of the droplet shape is given by the velocity potential equation. The Laplace equation for the velocity potential is solved by expanding the potential onto harmonic functions. For the part of the pathway dominated by electrostatic pressure, the calculations reproduce the experimental data nicely, obtained for both, glycol and water microdroplets. We find that the droplet shape and in particular the tips, just before charge emission, are well fitted by a lemon shape. We stress that the tip is tangent to a cone of 39°and thus significantly narrower than a Taylor cone.

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2003

In the present contribution we discuss the charge emission, the limit of stability as well as the... more In the present contribution we discuss the charge emission, the limit of stability as well as the role of quadrupole deformations in coulomb instabilities occurring in small charged objects. These are nano-systems, like highly charged sodium clusters with a diameter of about 50 nm, containing around 250 atoms as well as micro-systems, like microdroplets of ethylene glycol with a diameter of 50 lm, containing of the order of 10 12 glycol molecules. The experiments show that in the first case the internal energy limits the region of stability due to thermally activated fission processes, whereas it is unimportant for micro-droplets. In the latter case, the validity of the Rayleigh limit could be established for the first time experimentally. Furthermore, the different decay processes are discussed.

The European Physical Journal D - Atomic, Molecular and Optical Physics, 2003

ABSTRACT Highly charged sodium clusters produced in collisions between neutral clusters and multi... more ABSTRACT Highly charged sodium clusters produced in collisions between neutral clusters and multiply charged ions are formed within a large range of temperatures and fissilities, and identified by means of a high-resolution reflectron-type time-of-flight mass spectrometer ( m/m 14000). The limit of stability of these charged clusters is experimentally investigated, and the time-of-flight spectra are compared with theoretical spectra based on Monte-Carlo simulations. The results indicate that the maximum fissility (X) of stable clusters is approaching the Rayleigh limit (X = 1) for larger clusters sizes. It is mainly limited by the initial neutral cluster temperature ( T 100 K) and the energy transfer in the ionizing collision. In addition, the comparison between the measured and simulated spectra suggests for high cluster charges a multi-fragmentation process, in which most of charge is emitted, creating low charged residual cluster ions.