Wiktionary
n. (context physics English) The branch of physics concerned with dynamic processes that take place with a time resolution of the order of attoseconds
Wikipedia
Attophysics is a branch of physics wherein attosecond (10 s) duration pulses of electrons or photons are used to probe dynamic processes in matter with unprecedented time resolution. This branch of physics which involves studying some of the fastest physical events is also known as attoscience. The majority of attoscience employs pump–probe methods.
Today, attophysicists mostly study molecular phenomena, such as how a particular protein breaks down under X-ray bombardment. "One of the primary goals of attosecond science is to provide more insights into the dynamics of atomic electrons."