Equation of motion for electron oscillator: F net = F damping + F spring + F driving = m d 2 r d t 2 − − m τ τ d r d t − − k r − − e E ( t ) = m d 2 r d t 2 d 2 r d t 2 + 1 τ τ d r d t + ω ω 0 2 r = − − e m E ( t )