Absorption cross sections at the M(4,5) edges of rare earths: A soft X-ray transmission experiment

We have determined the absorption coefficients of several rare earths (Gd, Dy, Ho and Er) at the M(4,5) edges (3d --> 4f excitations) by measuring the soft X-ray transmission through layers of different thicknesses between 2 and 400 Angstrom. Our results are in good agreement with atomic calculations. We also compare transmission-derived absorption curves with spectra collected simultaneously in the standard total electron yield mode. Advantages and limitations of the transmission mode for soft X-rays and also its range of application are discussed.