Fit Function: na_ein_lotz

Fit Function \[\sigma_{e}^{ion, 2s,2p}(E) = A_1 A_2 10^{-14}\frac{\ln\big(\frac{E}{I}\big)}{EI} \Bigg[1 - A_3e^{-A_4\big(\frac{E}{I}-1\big)} \Bigg]\]
Comments Python code requires NumPy imported as `np`.

Python

Arguments
namedescriptionunitstype(s)
E impact energy eV float, np.ndarray
A1 fit coefficient cm eV float
A2 fit coefficient cm eV float
A3 fit coefficient float
A4 fit coefficient float
I ionization energy eV float
Return values
namedescriptionunitstype(s)
sigma cross section cm2 float, np.ndarray
Code 
def na_ein_lotz(E, A1, A2, A3, A4, I):
    """
    This function calculates electron impact ionization cross sections (in cm2) of 
    Na 2s to 2p.
    param E: requested electron-impact energy in eV
    type E: float, np.ndarray
    param Ai: fit coefficient 
    type Ai: float
    param I: ionization energy in eV
    type I: float
    """
    sigma =  1e-14 * A1 * A2 * (np.log(E/I) / (E*I)) * (1 - A3*np.exp(-A4*((E/I)-1)))
    return sigma