Total interaction cross sections and effective atomic numbers of some biologically important compounds containing H, C, N and O in the energy range 6.4–136 keV

Abstract

The total interaction cross sections (σt) of some sugars and amino acids and five elements: lithium, carbon, oxygen, aluminium and calcium have been measured for 6.4 keV, 13.95 keV, 14.4 keV, 17.74 keV, 24.14 keV, 30.8 keV, 35 keV, 59.54 keV, 81 keV, 122 keV and 136 keV photons in a narrow beam good geometry set up, by using high resolution detectors such as a Si-PIN diode detector and a high purity germanium detector. The σt values have been used in a matrix method to evaluate the effective atomic numbers Zeff of the samples from their effective atomic cross sections σa. The effective atomic cross section of a sample σa is the total interaction cross section divided by the total number of atoms of all types in it. Further, a quantity called the effective atomic weight Aeff of a sample was defined as the ratio of the molecular weight A to the total number of atoms of all types in it. The variation of Zeff was systematically studied with respect to Aeff as well as σa at each experimental energy separately and new semi-empirical relations for Zeff have been evolved. It is felt that these relations can be very convenient for determining the effective atomic number of any sample having H, C, N and O atoms in the energy range 6.4 keV–136 keV irrespective of its chemical structure.