| 1967 | Summer Research Program, Biochemistry Section, Central Research Department, Experimental Station, E. I. du Pont de Nemours & Co., Wilmington, DE; Research Director: Dr. C. C. McDonald |
| 1967-1968 | NSF Predoctoral Fellow |
| 1967-1968 | Woodrow Wilson Honorary Fellow |
| 1968-1969 | Fannie and John Hertz Fellow |
| 1972-1974 | Research Associate, Department of Chemistry, Columbia University, New York, New York; Research Director: Prof. R. N. Zare |
| 1974-1978 | Assistant Professor, Department of Chemistry, The Johns Hopkins University |
| 1976-1980 | Alfred P. Sloan Research Fellow |
| 1977-1982 | Camille and Henry Dreyfus Teacher-Scholar |
| 1979-1981 | Associate Professor, Department of Chemistry, The Johns Hopkins University |
| 1980-1981 | Consultant, McDonnell Douglas Research Laboratories, St. Louis, MO |
| 1981-present | Professor, Department of Chemistry, The Johns Hopkins University |
| 1981-1985 | Member, Review Board, Regional Laser Laboratories, University of Pennsylvania, Philadelphia, PA |
| 1982-1984 | Member, Editorial Board, The Journal of Chemical Physics |
| 1985-1991 | Eastern U.S. Editor, Laser Chemistry (Gordon and Breach Science Publishers) |
| 1985 | Vice-chairman, 1985 Conference on the Dynamics of Molecular Collisions, Snowbird, UT, July 14-19 |
| 1986-1995 | Senior Fellow, Center for Astrophysical Sciences, The Johns Hopkins University |
| 1986-present | Fellow, American Physical Society |
| 1987 | Chairman, 1987 Conference on the Dynamics of Molecular Collisions, Wheeling, WV, July 12-17 |
| 1987 | Member, Organizing Committee, NATO Advanced Workshop on Selectivity in Chemical Reactions, Bowness-on-Windemere, September 7-11 |
| 1988 | Participant, ARO Workshop on Nitramine Propellant Ignition and Combustion, Chapel Hill, NC, May 30-June 3 |
| 1988-1989 | Member, Program Committee, Quantum Electronics Laser Science Meeting, Baltimore, MD, April 24-28, 1989 |
| 1989-1990 | Vice-chairman, Division of Chemical Physics, American Physical Society |
| 1990-1992 | Chairman, Division of Chemical Physics, American Physical Society |
| 1990-1991 | Member, Program Committee, Quantum Electronics Laser Science Meeting, Baltimore, MD, May 13-17,1991 |
| 1992 | Member, Workshop on Local Measurement Techniques for Tropospheric OH and HO2, Menlo Park, CA, March 23-26 |
| 1992 | Member, William F. Meggers Award Selection Committee, Optical Society of America |
| 1993-1995 | Member, Canvassing Committee for the ACS Award in Pure Chemistry, American Chemical Society |
| 1995-1996 | Chairman, Canvassing Committee for the ACS Award in Pure Chemistry, American Chemical Society |
| 1995-1996 | Co-organizer, ACS Symposium on Bimolecular Interactions of Small Free Radicals, ACS National Meeting, Orlando, FL, August 25-29, 1996 |
| 1998-2005 | Chair, Department of Chemistry, The Johns Hopkins University |
| 1999-2000 | Member, Advisory Committee for the XXIV Informal Conference on Photochemistry, San Juan, PR, April 9 - 14, 2000 |
| 1999-2000 | Member, Advisory Committee for the Gordon Conference on Molecular Electronic Spectroscopy and Dynamics, July 30 - August 4, 2000 |
| 1999-present | Arthur D. Chambers Professor of Chemistry, The Johns Hopkins University |
| 2002 | Vice-chair, Gordon Conference on Atomic and Molecular Interactions |
| 2004 | Chair, Gordon Conference on Atomic and Molecular Interactions |
| 2004 | Participant, U.S.-Egypt Workshop on Laser Chemistry and Applications to Materials and Biomedical Research, Cairo, Egypt, October 2-5 |
| 2005-2006 | Member, Technical Program Committee, Laser Applications for Chemical, Security, and Environmental Analysis (LACSEA), Lake Tahoe, NV, February 5-9, 2006 |
| 2005-present | Adjunct Professor, Department of Chemistry and Biochemistry, University of Maryland, College Park |
| 2005-2006 | Visiting Fellow, JILA, University of Colorado |
| 2006 | Participant, Investment Strategy Meeting, Army Research Office, May 2-3 |
| 2006 | Member, Herbert P. Broida Prize Committee, American Physical Society |
| 2006 | Evaluator of Chemistry Department of St. Mary's College of Maryland for American Chemical Society Committee on Professional Training |
| 2006-2011 | Member, Homewood Schools Academic Council, The Johns Hopkins University |
| 2007 | Maryland Chemist of the Year, Maryland Section of the American Chemical Society |