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Manuscript Title: EMI: the counting efficiency for electron capture, electron capture- gamma and isomeric transitions.
Authors: A. Grau Carles, A. Grau Malonda, P. Grau Carles
Program title: EMI
Catalogue identifier: ACPU_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 79(1994)115
Programming language: Fortran.
Computer: IBM AT.
Operating system: MS-DOS 3.30.
Word size: 32
Keywords: Atomic physics, Experiment, Electron capture, Isomeric transition, Liquid scintillation, Counting efficiency.
Classification: 2.3.

Nature of problem:
The standardization in liquid scintillation counting of electron-capture nuclides (EC), EC coincident and non-coincident with gamma transitions and single isomeric transitions (IC) requires the determination of the counting efficiency. A detailed analysis of the different atomic rearrangements that follow the EC and IC processes, permits one to compute the counting efficiency as a function of a free parameter. However, the interaction of the energetic gamma and X-ray photons with the scintillator produce Compton electrons. Hence, the energy distribution for these electrons must be computed.

Solution method:
A simplified K, L and M three shell model is applied to compute the probabilities for the different pathways in the electron-capture and internal conversion processes. The reduced energy distributions for the photoelectric and Compton electrons are obtained by Monte Carlo techniques, which permit one to simulate the geometry and the chemical nature of the sample. These probabilites and reduced energies are used in the determination of the counting efficiencies.

The model assumes that the three L and the five M subshells can be averaged to L- and M-shells, respectively. The atomic rearrangement for M and higher shells is not considered.

Running time:
The test run requires about 80 seconds on an IBM AT.