Indexed on: 14 Mar '16Published on: 09 Mar '16Published in: Radiation Physics and Chemistry
Photon attenuation coefficient calculation methods have been widely used to accurately study the properties of amino acids such as n-acetyl-l-tryptophan, n-acetyl-l-tyrosine, d-tryptophan, n-acetyl-l-glutamic acid, d-phenylalanine, and d-threonine. In this study, mass attenuation coefficients (µm) of these amino acids for 0.122-, 0.356-, 0.511-, 0.662-, 0.884-, 1.170, 1.275-, 1.330-MeV photons are determined using the radio-nuclides Co57, Ba133, Cs137, Na22, Mn54, and Co60. NaI (Tl) scintillation detection system was used to detect gamma rays with a resolution of 8.2% at 0.662 MeV. The calculated attenuation coefficient values were then used to determine total atomic cross sections (σt), molar extinction coefficients (ε), electronic cross sections (σe), effective atomic numbers (Zeff), and effective electron densities (Neff) of the amino acids. Theoretical values were calculated based on the XCOM data. Theoretical and experimental values are found to be in a good agreement (error<5%). The variations of µm, σt, ε, σe, Zeff, and Neff with energy are shown graphically. The values of µm, σt, ε, σe are higher at lower energies, and they decrease sharply as energy increases; by contrast, Zeff and Neff were found to be almost constant.