# H atom ionization SFA

1. Apr 2, 2013

### ENDLESSYOU

Hi! I have some trouble with atomic unit. I have a laser pulse with the wavelength of $800 nm$ at the
peak intensity of $1.0*10^{14} W/cm^{2}$. I'd like to calculate the corresponding electric field $E_0$. I use the formula $I=0.5Cε_0{E_{0}}^2$ and $1 a.u.=5.14*10^{11} V/m$ to obtain $E_0=5.3*10^{-6}$, which is much smaller than the expected value 0.1.
Another question is about the energy spectra. It is written as $\frac{\partial P}{\partial E}$. Is the P here means the probability density or the probability?
Thanks!

2. Apr 2, 2013

### Staff: Mentor

Which units does E0 have and how did you calculate it? V/m is an electric field strength.
What do you mean with "expected value 0.1"?

Are you sure P is a probability, not a power? If yes, P would have to be a probability and its derivative in E is the density in E.