Fit Function: h_hex_janev_16

Fit Function \[\sigma_{ex}^{1\rightarrow 3,4,5,6}(E)=10^{-16}A_1 \Bigg[\frac{e^{-\frac{A_2}{E}}\ln(1+A_3E)}{E} + \frac{A_4e^{-A_5E}}{E^{A_6} + A_7E^{A_8}}\Bigg]\]
Comments Python code requires NumPy imported as `np`.

Python

Arguments
namedescriptionunitstype(s)
E impact energy keV u-1 float, np.ndarray
A1 fit coefficient keV cm2 u-1 float
A2 fit coefficient keV u-1 float
A3 fit coefficient keV-1 u float
A4 fit coefficient undef float
A5 fit coefficient keV-1 u float
A6 fit coefficient float
A7 fit coefficient undef float
A8 fit coefficient float
Return values
namedescriptionunitstype(s)
sigma cross section cm2 float, np.ndarray
Code 
def h_hex_janev_16(E, A1, A2, A3, A4, A5, A6, A7, A8):
    """
    This function calculates proton impact excitation cross sections (in cm2) of 
    H n=1 to n=3,4,5,6 and He+2 impact of n=1 to n=5,6.
    param E: requested impact energy in keV/u
    type E: float, np.ndarray
    param Ai: fit coefficient 
    type Ai: float
    """
    sigma = 1e-16 * A1 * (np.exp(-A2/E) * np.log(1 + A3*E) / E + 
                    A4*np.exp(-A5*E)/ (E**A6 + A7*E**A8))
    return sigma