Physics Colloquium, May 29, 2007
Muybrige's galloping horse Pierre Agostini

The Ohio State University, Department of Physics

Around 1878, there was a question popularly debated by the race track community: "are a horse four hooves simultaneously off the ground during gallop"? It was definitely answered by Eadward Muybrige, a photographer from San Francisco, now famous for his sequences of stop-motion snapshots. Molecules travel much faster than horses and, in the 1950's, the important issue of "how fast do chemical reactions occur?" triggered the invention of new methods. Flash lamps, used to excite and probe photochemical reactions in the millisecond to microsecond time-scale, opened the field of "microchemistry". For the 1999 Nobel Prize, Ahmed H. Zewail, the next question was "How does the energy put into a reactant molecule redistribute among the different degrees of freedom, and how fast does this happen"? Laser time-domain spectroscopy with femtosecond (10^-15s) resolution, possible since the mid seventies brought the answer. The next question could be: "how and how fast do atomic electrons rearrange following a sudden perturbation"? After the breaking of the femtosecond barrier in 2001, soft X-ray pulses close to 100 as (1as=10^-18s) are now available. Attosecond light pulses are seen as opening a new regime in ultrafast physics and the obvious tool to resolve one and two-electron dynamics in the time domain.

Dr. Agostini's Web Site

4:00 p.m., Physics Research Building (PRB), Room 1080

Reception at 3:45 p.m., Atrium, PRB