flag compounds with resonances in the thermal neutron range

[pkienzle]

Point users to appropriate literature if they choose a compound with rare earths. A link should appear on the table indicating that the calculator should not be used for these values, and an explanation why.

Even better: update the periodictable calculator so that it computes things correctly based on wavelength.

Here's a response I wrote re: the use of Eu in a compound:

Eu-151 has resonances in the thermal range; with 48% natural abundance, the factor of 4 range for the total scattering cross section. Therefore the value that appears in the tables is highly dependent upon the energy at which they are tabulated.

The activation calculator is using the following table, which lists Eu with a bound coherent cross section of 5.3 +/- 0.3:

LANDOLT-BÖRNSTEIN, New Series I/16A (Ed. H. Schopper) Chap.6, Springer, Berlin 2000
Atomic Data Nuclear Data Tables 49 (1991) 65

http://www.ati.ac.at/~neutropt/scattering/table.html

The table you are looking at is using data from the following:

Neutron News, Vol. 3, No. 3, 1992, pp. 29-37

See the following for Eu in particular and all rare earths:

http://dx.doi.org/10.1107/S0021889889006400
http://dx.doi.org/10.1016/0092-640X(90)90013-A

Table of all isotopes with natural abundance that have resonance peaks below 0.1 A:

https://www.ncnr.nist.gov/resources/activation/resonance.html