* Understand femtoseconds: A femtosecond (fs) is a unit of time equal to 10^-15 seconds.

* Scientific notation: Scientific notation expresses a number as a product of a number between 1 and 10 and a power of 10.

Here's the conversion:

7 femtoseconds = 7 x 10^-15 seconds

Therefore, 7 femtoseconds in scientific notation is 7 x 10^-15 seconds.