Dear members, I have seen many times the absorption length in materials for introduction of XAFS. The absorption length equals 1/mu, which is the thickness that I0 is attenuated to 1/e. But I do not understand why the absorption length is important. More importantly, I do not understand why the particle size in samples should be smaller than the absorption length. Could any one explain the absorption length including the question above and the relation between the absorption length and edge step calculations? Thanks in advance. Kug-Seung Lee Kug-Seung Lee, Ph.D. Staff Scientist Manager, 8C Nano Probe XAFS Beamline Pohang Accelerator Laboratory Pohang 790-784, Republic of Korea Office: +82-54-279-1522 Fax: +82-54-279-1599 C. P.: +82-10-6419-7801 Researcher ID: http://www.researcherid.com/rid/D-7088-2011