fs

femtosecond

Timeexact by definition

The femtosecond is 10⁻¹⁵ of a second, an exact SI prefix. It is the natural clock of chemistry: a molecular bond vibrates once every 10 to 100 femtoseconds, so a femtosecond pulse can photograph a chemical reaction while it is still happening. Light travels just 0.3 micrometres in one.

1 fs 1.0000000e-15 s
Where the unit came from

Femtochemistry, built on this unit, earned Ahmed Zewail the 1999 Nobel Prize in Chemistry for watching bonds break in real time rather than inferring the result afterwards.