Noun
one quintillionth (10^-18) of a second; one thousandth of a femtosecond
Source: WordNetTheir tests involved tunneling electrons, where the group argued a relativistic prediction for tunneling time should be 500-600 attoseconds (an attosecond is one quintillionth (10 18 ) of a second). Source: Internet
The scientists used extremely short flashes of light, called attosecond pulses, which allowed an electron's motion to be observed for the first time. Source: Internet