A value calculated from the energy emitted by an excited metal (Cu or Mo) and captured (absorbed) by the substance. The calculated value is the mass absorption coefficient.
Electron capture or K capture is a process involving the capture of a K electron ejected by a target metal. A Coolidge tube. with a tungsten target may be used to excite the K lines of Molybdenum or Copper expressed as the MoK or CuK line or wavelength. The energy emitted by the copper or molybdenum is in the X-Ray region.