Studies on Photon Interaction Parameters of Some Fluorescent Molecules

In the interaction of photons using the WinXCom program, the parameters for the three fluorescent molecules, 5NFMOT, 4ATMBC, and 4ATMMC, the effective atomic number (Z_eff), and electron density (N_el), have been determined for the energy range of 1–100 GeV using mass attenuation coefficients. The variation of \(\mu /\rho\) $\mu /\rho$ , Z_eff , and N_el values for the energies are graphically depicted for different photon interactions. The variation of both parameters, Z_eff and N_el , with energy is the same. The significant fluctuation in Z_eff and N_el can be attributed to the prevalence of several interaction mechanisms within that energy range. For example, photoelectric absorption takes place at energies lower than 0.01 MeV. Pair formation steadily rises and achieves a constant value at energies above 100 MeV, while Compton scattering starts at 0.01 MeV and continues until it reaches 0.05 MeV. Additionally, kerma (k_a) values for a range of energies between 1 keV and 20 MeV have been found. Photoelectric absorption for kerma (k_a) seems to be the predominant interaction method for fluorescent compounds. There are biological and therapeutic uses for these Z_eff, N_el, and k_a values.

In the wide energy region, variation of photon interaction parameters with energies has been explained. The presence of several interaction modes in that energy range accounts for the significant variation in Z_eff. The primary process of interaction at low energy, or at E < 0.01 MeV, is photoelectric absorption. Within the intermediate energy area, 0.01 MeV < E > 0.05 MeV, Compton scattering is the main interaction mechanism and pair production dominates above at E > 100 MeV. The absorption peak shown by kerma values in the energy range has been detected at 80 keV, where the primary interaction process seems to be photoelectric absorption.