Sub‐picosecond spectroscopy

Ever since Man first became interested in movements and events that occurred too rapidly for his eye to follow, short flashes of light have been used to isolate moments of time. Each time shorter light pulses have become available, new areas of research have opened up, and new types of ultafast processes have become amenable to study. Spark photography can freeze the most rapid movement of macroscopic objects with flashes a tenth of a microsecond in duration. High‐speed flashlamps and electronics play an important role in the study of fast photophysical and photochemical reactions with a resolution of a tenth of a nanosecond—$10−10 sec.$ The last decade has seen dramatic advances in the development of short laser pulses and their application to the study of picosecond phenomena. Now, the extension of this technology into the sub‐picosecond $(10−13 sec)$ regime offers exciting possibilities for accurate studies of previously unresolved, ultrafast photoprocesses in physics, chemistry and biology. Investigations are being extended to such diverse and important topics as the vibrational dynamics of molecules and lattices, primary photobiological mechanisms and picosecond electronic processes in semiconductors.