t = linspace(0,20,1000);

tau_s = 0.8926*10^-10;
tau_l = 5.17*10^-8;
w     = .5333*10^10;
w = 10*w;

t_real = tau_s*t;

i = 0.25*(exp(-t_real/tau_s)+exp(-t_real/tau_l)-2*exp(-t_real/2*(1/tau_s+1/tau_l)).*cos(w*t_real));

plot(t,i);