Fit Function: SPTEEX

Fit Function \[Y(E) = \frac{q}{2} \frac{\left( \frac{E}{E_\mathrm{th}} - 1 \right)^\mu \ln(1 + 1.2288\epsilon)}{\lambda + \left( \frac{E}{E_\mathrm{th}} - 1 \right)^\mu \left[ \epsilon + 0.1728\sqrt{\epsilon} + 0.008\epsilon^{0.1504} \right]}\]
Comments Note: this formula is given incorrectly in its cited reference of Eckstein, p.38, eqn (2).

Python

Arguments
namedescriptionunitstype(s)
E projectile energy eV float, np.ndarray
lambda fit coefficient float
q fit coefficient float
mu fit coefficient float
epsilonL fit coefficient: the reduced energy, epsilon = E / epsilonL eV float
Eth fit coefficient: the threshold energy for sputtering eV float
Return values
namedescriptionunitstype(s)
Y(E0, alpha) sputtering yield float, np.ndarray
Code 
def spteex(E0, lam, q, mu, epsilonL, Eth):
    """Revised Bohdansky formula, e.g. APID-7B, p.18. """
    epsilon = E0 / epsilonL
    factor = (E0 / Eth - 1) ** mu
    num = factor * np.log(1 + 1.2288*epsilon)
    den = lam + factor*(epsilon + 0.1728*np.sqrt(epsilon) + 0.008*epsilon**0.1504)
    return 0.5 * q * num / den