def cm2nm(E_cm):
    """Converts photon energy from absolute cm-1 to wavelength

            Parameters
            ----------
            E_cm: float
                  photon energy in cm-1

            Returns
            -------
            float
                 Photon energy in nm

            Examples
            --------
            >>> cm2nm(1e5)
            100
            """
    return 1 / (E_cm * 1e-7)