def sf_machine(sf_wagner, transmission_mach, transmission_wagner):
    """Sensitivity factor for XPS machine correction from the Wagner XPS machine

    sf_wagner              : Wagner sensitivity factor
    transmission_mach      : Transmission function for the selected element
    transmission_wagner    : Wagner transmission function for the selected
                             element.
                             Proportional to 1/(kinetic_energy) [1/eV]
    """
    return sf_wagner * transmission_mach / transmission_wagner
