THE EFFECTS OF VIBRATIONAL AND ROTATIONAL MOTION ON THE FIELD DISSOCIATION BY ATOMIC TUNNELING OF HeRh2 IONS

When a compound ion is placed in an intense electric field, the potential barrier may be lowered to the extent that dissociation can occur via quantum mechanical tunneling (1). We have made a numerical study of the detailed atomic process of dissociation. When the molecular ion, HeRh2+, is field evaporated from the surface, it cannot dissociate since it is in the wrong orientation. As the molecular ion rotates and vibrates, the probability of dissociation becomes non-zero when the angle of rotation lies in the range 90° < θ < 270°. The model calculations predict the existence of a field dissociation zone of width 124 Å with the peak in the dissociation located at 197 Å above the surface. These results are in excellent agreement with the experimental data of Tsong and Liou (2,3). In addition, the model calculations predict four dissociation peaks within this zone due to the vibrational motion of the ion. These fine structure lines in the secondary Rh2+ peak are separated on the average by 0.86x10-13 sec, implying an average vibrational frequency of 1.2x1012 Hz. Their relative intensities are 0.356, 1.00, 0.784, and 0.235. These fine structure lines in the secondary Rh2+ peak should be experimentally observable provided the stability and the resolution of the atom-probe are further improved by a factor of about five. We are in the process of making an improvement so that the vibrational features in the field dissociation can be directly observed in the time-of-flight spectrum

Theoretical Analysis of a Geis-Spindt Cold Cathode Diamond Emitter

A quantitative theory for the operation of a Spindt-type cold cathode emitter embedded in a thin diamond film doped with substitutional Nitrogen is presented. The device, recently developed by M. W.Geis and colleagues at the MIT Lincoln Laboratory, is characterized by high field emission currents at low power. The theoretical model treats injection, by internal field emission, at the metal-diamond interface, transport through the diamond film and emission at the diamond-vacuum surface. The calculated 1-V characteristics agree well with the experimental results of Geis et al

A HYDRODYNAMICAL STUDY OF THE INSTABILITY OF A PLANAR LIQUID METAL ION SOURCE (SUMMARY)

Liquid metal ion sources (LMIS) are of interest in diverse areas of technology since they provide a high brightness, quasi-point source of ions for high resolution ion beam lithography, microfabrication, surface analysis and other potential applications[l]. The technical difficulties of building and operating stable sources have been largely overcome. The basic physics of source operation and ion formation is, however, still incompletely understood. Krohn and Ringo first described the fundamental processes of ion emission from liquid metal tips in a strong electric field[2]. Subsequently, Gomer[3] and others[4-8] analyzed the mechanism of LMIS and developed theoretical models to explain the shape and size of the ion emitting region