Mass Absorption Coefficient

["David Scherer" <DAVID@speedy.ehs.uiuc.edu>]

One additional clarification may be in order.  One responder said he 
had not heard of the "mass" absorpion coefficient.  It is the linear 
absorption coefficient (e.g. cm-1) divided by the density (g cm-3).  
This is entirely analogous to the linear and mass ATTENUATION 
coefficients, in which the photoelectric, Compton, and pair production 
cross sections are not modified for the energy carried away by 
secondary photons.  As with many basic topics, Robley Evan's _The 
Atomic Nucleus_ has an excellent explanation.

David Scherer
scherer@uiuc.edu