No abstract

C84+ and coronene (C24H12+) have been studied as primary ions for use in secondary ion mass spectrometry. A representative range of samples has been used to compare the effectiveness of each primary ion with the existing C60+, Au+, and Au3+ primary ions. It was found that C84 is the most effective primary ion providing higher secondary ion yields and a high molecular to fragment ion ratio. Coronene had a performance similar to C60. Coronene and C60 primary ions were also used to extend a previous study of matrix suppression/enhancement effects. The C60 was found to ameliorate this effect, possibly due to the increase in protonation in polyatomic sputtering, and coronene was found to further reduce suppression showing evidence of a chemical effect.

Application of an electric field to microspheres, dispersed in a nematic liquid crystal host material, causes particle translation along the direction of the average long molecular liquid crystal axis, i.e., the director. We have determined the stability regime of linear particle displacement in the parameter space of electric field amplitude and frequency for various applied electric wave forms and demonstrate a linear relationship between microsphere velocity and applied electric field amplitude. For increasing frequency the particle velocity exhibits a maximum before motion slowly vanishes. Addition of a small amount of an ionic dopant is shown to largely increase the stability region of linear microsphere motion, with particle velocities increasing until saturation is observed for increasing ion dopant concentration. It is presumed that the particle velocity is related to the surface charges adsorbed on the dispersed particles. Also the dynamics of occasionally observed two- and three-particle clusters is discussed.