1. Department of Medical and Health Sciences, Radiation Physics, Faculty of Health Sciences, Linkoping University, S-58185 Linkoping, Sweden, On leave from Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Cracow, Poland, and Department of Chemistry and Biochemistry, University of Detroit Mercy, 4001 West McNichols Road, Detroit, Michigan 48221-3038