(http://www.kitlaser.com/1000mw-new-earthly-gold-green-laser-p.html) Of course, in the femtoosond time scale, it is impossible to observe the change of the energy state of electrons directly, therefore, the scientific by measuring the material to reflect the change in light to achieve the purpose of indirect observation - first with high- Power after the occurrence of a weak laser pulse and the reflected light measurement.
