- Thin film generation of novel materials
- Mass spectrometry of clusters
- B. S. and M. S., Georgetown University (1978)
- Ph.D., California Institute of Technology (1985)
- Postdoctoral Scholar, University of California, Los Angeles (1985-87)
- Alfred P. Sloan Fellow (1991-93)
- Fulbright Fellow, University of Sussex, United Kingdom (1994,1996)
Thin Film Generation of Novel Materials, Mass Spectrometry of Clusters
Our group is interested in utilizing state-of-the-art mass spectrometric techniques to explore chemical reactions within gas-phase clusters (i.e., {CH3OH}n{H2O}H+, {C2H4}n+, etc.). We currently have five different experiments in order to study a wide variety of chemical systems:
- a continuous cluster beam source mated to a high resolution triple quadrupole mass spectrometer,
- a pulsed cluster beam source used in conjunction with a reflectron time-of-flight mass spectrometer for multiphoton studies,
- a metal cluster source used for the generation of thin films, utilizing a quadrupole mass spectrometer for beam diagnostics,
- a triple quadrupole mass spectrometer for the study of fullerene (C60) ion chemistry,
- a ZAB-SE tandem mass spectrometer which is used to conduct dissociation experiments on metallofullerene species (Sc@C60).
In addition, we have two separate excimer laser systems which are employed as photoionization sources and can be used with any of the five mass spectrometric instruments.
Our molecular beam experiments consist of generating a stream of van der Waals clusters, via a supersonic expansion, in a wide distribution of cluster sizes (n = 2-200). Then, we generate a cation within the cluster, which spontaneously reacts with one (or more) of the solvating neutrals, creating a new cluster ion. The product of this cluster chemistry we directly detect via mass spectrometry. By observing how the distribution of product ions vary as a function of clustersize, we can then deduce the chemical reactions which occurred within the cluster. More importantly we can observe how this chemistry changes as a function of cluster size (i.e., that is, how does solvation effect the course of a chemical reaction).
By concentrating on the chemistry within these cluster systems, it is possible to learn how the behavior of the system changes from that of a gas-phase bimolecular ion-molecule reaction to a typical chemical process within solution. Thus, the study of reactive processes in clusters may be used as a conceptual bridge between the gas-phase "bimolecular" world and the "solvated multimolecular" world of chemical reactions in solution.
This bridge has in fact turned into a crossroads, in that our work at SUNY has demonstrated that new chemical reactions can occur within the environment of a molecular cluster. This novel chemistry occurs due to the fact that unstable intermediates may be stabilized within the solvating environment of the cluster, on a long enough time scale such that they can undergo unusual chemistry. The observation of these unique processes which occur only within a cluster, is particularly exciting in that we may now utilize clusters as a novel "crock-pot" in which to do new chemistry.
An important new extrapolation of this work is to now attempt to use these clusters to generate new bulk materials, in the form of thin films. By utilizing our knowledge concerning the design and control of molecular beam expansions, we are capable of "spraying" clusters onto a particular substrate which then coalesce to generate a uniform coating. Through this technique of laser assisted molecular beam deposition (LAMBD) we hope to tailor the experimental conditions to produce a variety of films with industrial and electronic applications (superconducting thin films, diamond-like carbon thin films, patterned or multi-layered thin films, wide bandgap semiconductors, etc.). This work is summarized in the following drawings.
Selected Recent Publications