what is attosecond

An attosecond is a unit of time in the International System of Units (SI) equal to 1×10−18 of a second (one quintillionth of a second). For comparison, an attosecond is to a second what a second is to about 31.71 billion years. The word "attosecond" is formed by the prefix atto and the unit second. Atto- was derived from the Danish word for eighteen (atten). An attosecond is equal to 1000 zeptoseconds, or 1⁄1000 of a femtosecond. Attosecond physics is a branch of physics that deals with light-matter interaction phenomena wherein attosecond photon pulses are used to unravel dynamical processes in matter with unprecedented time resolution. Attosecond science mainly employs pump–probe spectroscopic methods to investigate the physical process of interest. The main interests of attosecond physics are to control electron motion on its natural (attosecond) time scale and to carry out direct attosecond pump/attosecond probe measurements.