Fit Function: singlet_triplet_H2

Fit Function \[\sigma (x) = \Bigg| \frac{x - 1}{x} \cdot \left(\frac{A_1^2}{x} + \frac{A_2}{x^2} + \frac{A_3}{x^3} + \frac{A_4}{x^4} + \frac{A_5}{x^5}\right)\Bigg|\]
Comments Python code requires NumPy imported as `np`.

Python

Arguments
namedescriptionunitstype(s)
x requested energy in threshold units float, np.ndarray
A1 fit coefficient float
A2 fit coefficient float
A3 fit coefficient float
A4 fit coefficient float
A5 fit coefficient float
Return values
namedescriptionunitstype(s)
sigma cross section a02 float, np.ndarray
Code 
def singlet_triplet_H2(x, A1, A2, A3, A4, A5):
    """
    This function calculates the vibrational and dissociative excitation cross sections 
    (in a.u.) of H2 isotopologues from the ground electronic state X to triplet excited 
    states above the b(3SIGMA+u) state.

    param x: requested electron-impact energy in threshold units
    type x: float, np.ndarray
    param Ai: fit coefficients
    type Ai: float
    """
    sigma = ((x-1)/x)*(A1**2/x + A2/x**2 + A3/x**3 + A4/x**4 + A5/x**5)
    return np.absolute(sigma)