The structure factor of polydisperse magnetic fluids

This work is devoted to the development of the theoretical model, permitting to find the pair correlation function and the structure factor of magnetic fluids taking into account the polydispersity of magnetic particles. The magnetic fluid was modeled as a system of bidisperse dipolar hard spheres. We compared the results obtained on the basis of monodisperse and bidisperse models. The consideration of the particle polydispersity affects the behavior of the structure factor: the value of the first peak decreases and becomes broader in comparison to the monodisperse case.     

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.