Fit Function: li_hel_nl_schweinz

Fit Function \[\sigma_{H^+}^{TEL, \;Li(l>0)}\big(E\big) = 10^{-14}A_1 \Big(1- \big(e + A_3E\big)^{-A_2/E}\Big)\]
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 float
A3 fit coefficient keV-1 float
Return values
namedescriptionunitstype(s)
sigma cross section cm2 float, np.ndarray
Code 
def li_hel_nl_schweinz(E, A1, A2, A3):
    """
    This function calculates proton impact ionization cross sections (in cm2)
    from l>0 states of Li.
    param E: requested proton-impact energy in keV/u
    type E: float, np.ndarray
    param Ai: fit coefficient 
    type Ai: float
    """

    sigma = 1e-14*A1*(1 - (np.exp(1) + A3*E)**(-A2/E))
    return sigma