for

C.T. Chantler, School of Physics, University of Melbourne

Parkville, Victoria 3052, Australia

The tabulation has been produced as a J. Phys. Chem. Ref. Data publication [1] and as NIST database 66 - FFAST [2]. This erratum does not affect the body of the tabulation, i.e., the figures are completely unaffected and the tabulated values of

**1. Absorption edge precision**

Some comment has been received regarding the accuracy of energies of absorption edges. Since this is where the errors have been introduced it is useful to address this. Accuracies of edge positions are limited by chemical shifts and the detailed structure of the experimental material observed. Usually an accuracy of absolute energies below 1 - 3 eV is unattainable for this reason. At low energies (less than 200 - 500 eV) the occurrence of collective valence effects and dipole resonances can lead to much larger deviations (up to e.g., 50 eV or 10%).

L_{II} to L_{III}
energy separations are well understood
theoretically, and yet the tabulation claims that these energy
separations are 0 eV for *Z*=7 (N) to *Z*=14 (Si). Better estimates
of these separations for *Z*=12 to *Z*=14 are 0.4 eV, 0.4 eV and
0.6 eV. For *Z*=11 and below, the separations are 0.1 eV or less;
and in this range the separation is much less than the absolute
energy precision. Discrepancies of the absolute energies with
respect to other sources reveal uncertainties of 3 eV for Ne
L_{II}, 0.7 eV for
Na L_{II} and 1.8 eV for
Mg L_{II}, for
example. These are commensurate with uncertainties enumerated above.
Similarly, the M_{II} and M_{III} edges for Cl through to Zn
(*Z*=17-30) will be separated by up to 2.8 eV, and the M_{IV}
and M_{V} edges for Zn (*Z*=30) to Kr (*Z*=36) are separated by up
to 1.2 eV, as opposed to the common values given in Table 1,
Ref. 1 and Ref. 2. These separations are similarly below
1-3 eV and hence are consistent with the uncertainties listed.

The edge energies used are not derived from theory but are based on earlier experimental data [1]. Hence they should be consistent with the estimated experimental uncertainties - as they are. The reader was commended to allow for a shift of particular edge energies where the chemical shift in the structure of interest was known to a greater precision than those in the tabulation. However, this should be done with care, if at all, since the data only separates the K shell attenuation from the other shells - for convenience and length constraints it does not give separate orbital dependencies.

The author would like to acknowledge comments and responses from several colleagues, but in particular would like to thank Dr. J.-L. Staudenmann at NIST for a detailed critique which has accelerated the presentation of this erratum.

**References:**

- C.T. Chantler, "Theoretical Form Factor, Attenuation and Scattering
Tabulation for Z = 1-92 from E = 1-10 eV to
E = 0.4-1.0 MeV," J. Phys. Chem. Ref. Data
**24**, 71-643 (1995). - NIST Database 66: FFAST - Form Factor Attenuation Scattering Tables, Version 1, July 1995, from Ref. 1, C.T. Chantler (no longer available as a PC database; previously distributed by the NIST Standard Reference Data Group).

Online: April 1999