ABSTRACT
Photosynthesis is a complex process that involves multiple phenomena occurring on time scales ranging from femtoseconds to years. Following and characterizing the slow processes of photosynthesis has been a relatively accessible task since the beginning of photosynthesis research. On the other hand, resolving the fast processes has been crucially dependent on the availability of the light sources, producing pulses that are shorter than the investigated processes. The millisecond and nanosecond domains became accessible in the 1960s, but entering the femtosecond domain awaited until the dawn of the femtosecond lasers in the late 1980s (Zewail, 1998). The possibility to follow the processes occurring on picosecond and femtosecond time scales was certainly a breakthrough in the photosynthesis research. It opened the time window into the key initial photosynthetic processes, such as energy transfer in light-harvesting proteins and fast electron transfer in reaction centers. Since the 1990s, femtosecond spectroscopy has become a standard technique for studying the initial processes in photosynthesis. Today in the femtosecond spectroscopy laboratories, time resolution better than 50 fs is routinely reached, with a broad variety of pulse energies and repetition rates, and a spectral range that covers from the deep UV to the infrared region.
