Secondary ion yields produced by keV atomic and polyatomic ion impacts on a self-assembled monolayer surface

A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd.     

Solubility of hydrocarbons in water: Experimental measurements and modeling using a group contribution with association equation of state (GCA-EoS)

In this communication, new experimental data on the solubility of n-hexane, cyclo-hexane and iso-octane in pure water are reported. The data have been measured using a static-analytic technique that takes advantage of a Rolsi™ sampling device in the temperature range of 298–353 K and at pressures up to 0.5 MPa. The experimental data measured in this work at 298 K have been compared with some selected data from the literature and good agreement is found. A group contribution plus association equation of state, namely the GCA-EoS, is used to model the phase equilibrium of water + hydrocarbon (C₂ to n-C₆, cy-C₆, i-C₄ and i-C₈) system. The predictions of the model are found in good agreement with the experimental data measured in this work and some selected data from the literature.     

Some issues in soft SUSY-breaking terms from dilaton¦moduli sectors

We study the structure of the soft SUSY-breaking terms obtained from some classes of 4-D strings under the assumption of dilaton/moduli dominance in the process of SUSY-breaking. We generalize previous analyses in several ways and in particular consider the new features appearing when several moduli fields contribute to SUSY breaking (instead of an overall modulus T ). Some qualitative features indeed change in the multimoduli case. A general discussion for symmetric Abelian orbifolds as well as explicit examples are given. Certain general sumrules involving soft terms of different particles are shown to apply to large classes of models. Unlike in the overall modulus T case, gauginos may be lighter than scalars even at the tree-level. However, if one insists in getting that pattern of soft terms, these sum rules force some of the scalars to get negative mass². These tachyonic masses could be a problem for standard model 4-D strings but an advantage in the case of string-GUTs. We also discuss the possible effects of off-diagonal metrics for the matter fields which may give rise to flavour-changing neutral currents. Different sources for the bilinear B soft term are studied. It is found that the Giudice-Masiero mechanism for generating a “μ-term”, as naturally implemented in orbifolds, leads to the prediction ¦tgβ¦=1 at the string scale, independently of the Goldstino direction.