1975	Postdoctoral Fellow, City College of the City University of New York, Physics Department
1975-1978	Postdoctoral Fellow, Johns Hopkins University, Department of Biophysics
1984-1985	Visiting Professor, University of Palermo (Italy), Department of Physics
1985	Visiting Professor, University of Pavia (Italy), Dept. of Electronic Division of Applied Physics
1991-1992	Visiting Scholar, Stanford University, Department of Chemistry
1993	Visiting Professor, University of Palermo (Italy)
2000	Visiting Professor, CNR (National Research Council) , Palermo, Italy
2006	Visiting Professor, CNR (National Research Council) , Palermo, Italy