COEFICIENTE ISOMERICO CROSS SECTIONS ISOMER RATIO NUCLEAR REACTION YIELD RENDIMIENTO DE LAS REACCIONES NUCLEARES SECCIONES EFICACES ANTIMONY 121 TARGET ATOMIC SHELLS (K) BLANCO DE ANTIMONIO 121 BREMSSTRAHLUNG CAPAS ATOMICAS (K) CERIO 137 CERIUM 137 CESIUM 131 ELECTRONIC STRUCTURE ESPECTROS GAMMA ESTADOS EXCITADOS ESTRUCTURA ELECTRONICA EXCITED STATES GAMMA RADIATION GAMMA SPECTRA HIERRO 55 INTERNAL BREMSSTRAHLUNG IRON 55 ISOMERIC NUCLEI Internal bremsstrahlung spectrum accompanying 1S electron capture in decay of Fe 55, Cs 131, and Tl 204 MERCURY 197 NUCLEAR REACTIONS|REACCIONES NUCLEARES NUCLEOS ISOMEROS RADIACION DE FRENADO