Fit Function: h_hcx_javen_he_scaled

Fit Function \[\sigma_{CX}^{n>2}(E) = A_5^4 \frac{7.04 \times 10^{-16} A_1 \bigg[1 - e^{-\frac{4}{3A_1}\big(1 + \tilde E^{A_2} + A_3 \tilde E^{3.5} + A_4 \tilde E^{5.4}\big) } \bigg]}{1 + \tilde E^{A_2} + A_3 \tilde E^{3.5} + A_4 \tilde E^{5.4}}, \tilde E = EA_5^2\]
Comments Python code requires NumPy imported as `np`.

Python

Arguments
namedescriptionunitstype(s)
E impact energy keV u-1 float, np.ndarray
A1 fit coefficient cm2 float
A2 fit coefficient keV-1 u float
A3 fit coefficient undef float
A4 fit coefficient undef float
A5 main quantum number float
Return values
namedescriptionunitstype(s)
sigma cross section cm2 float, np.ndarray
Code 
def h_hcx_javen_he_scaled(E, A1, A2, A3, A4, A5):
    """
    This function calculates He+2 impact charge exchange cross sections (in cm2) of 
    H n > 2
    param E: requested impact energy in keV/u
    type E: float, np.ndarray
    param Ai: fit coefficient 
    type Ai: float
    """
    E = E/A[4]**2

    sigma = 7.04e-16*A5**4*A1*(1-np.exp(-4/(3*A1)* 
                   1+E**A2+A3*E**3.5+A4*E**5.4)))/(1+E**A2+A3*E**3.5+A4*E**5.4)
    return sigma