Biomedical subjects

C Guet

Publications and source records attributed to C Guet.

13 recordsLinked to original sources

PubMed2002

Shape oscillations and stability of charged microdroplets.

Classical Rayleigh theory predicts an instability of a surface charged liquid sphere, when the Coulomb energy E(C) exceeds twice the surface energy E(S). Previously, electrified liquid droplets have been found to disintegrate at a fissility X=E(C)/2E(S) well below one, however. We determine the stability of charged droplets in an electrodynamic levitator by observing the amplitude and phase of their quadrupolar shape oscillations as a function of the fissility. With this novel approach, which does not rely on an independent determination of the charge and surface tension of the droplets, we are able to confirm for the first time the Rayleigh limit of stability at X=1 for micrometer sized droplets of ethylene glycol.

Journal Article↗

PubMed2001

Rayleigh instabilities in multiply charged sodium clusters.

The stability of multiply charged sodium clusters Na(q+)(n) (q< or =10) produced in collisions between neutral clusters and multiply charged ions A(z+) ( z = 1 to 28) is experimentally investigated. Multiply charged clusters are formed within a large range of temperatures and fissilities. They are identified by means of a high-resolution reflectron-type time-of-flight mass spectrometer (m/deltam approximately 14 000). The maximum fissility of stable clusters is obtained for z = 28 and is X approximately 0.85+/-0.07, slightly below the Rayleigh limit (X = 1). It is mainly limited by the initial cluster temperature (T approximately 100 K).

Journal Article↗

PubMed2001

Charge-induced fragmentation of sodium clusters.

The fission of highly charged sodium clusters with fissilities X>1 is studied by ab initio molecular dynamics. Na4+24 is found to undergo predominantly sequential Na+3 emission on a time scale of 1 ps, while Na(Q+)(24) ( 5< or =Q< or =8) undergoes multifragmentation on a time scale > or =0.1 ps, with Na+ increasingly the dominant fragment as Q increases. All singly charged fragments Na(+)(n) up to size n = 6 are observed. The observed fragment spectrum is, within statistical error, independent of the temperature T of the parent cluster for T< or =1500 K. These findings are consistent with and explain recent trends observed experimentally.

Journal Article↗

PubMed2000

Temperature dependence of the polarizability of sodium clusters

We calculate the static dipole polarizability at finite temperature of sodium clusters of size 8, 20, 40, 55, 93, and 139 using an extended Thomas-Fermi description of the valence electrons. We find polarizabilities at 300 K that are roughly 15% greater than at 0 K, consistent with discrepancies between theoretical polarizabilities at 0 K and measured polarizabilities. We predict that a sharp rise in the polarizability, of about 5%, occurs for sizes of 55 and 139 when the cluster melts, offering the possibility of an alternative method for measuring cluster melting points.

Journal Article↗

PubMed1995