Decay of 99Mo- 99mTc

Abstract

The decay parameters of 99Mo 99mTc have been determined using liquid-liquid extractions, 4π β-γ and γ-γ coincidence counting and absolute gamma-spectroscopy measurements. Gamma-ray energies and intensities were obtained with a 7.6 cm × 7.6 cm NaI(Tl) spectrometer. The relative intensities of the 0.74 and 0.78 MeV gamma rays were measured using a lithium ion-drifted germanium detector (these peaks were unresolved in the NaI(Tl) spectra). The observed number of gamma photons per 99Mo disintegration with energies of 0.93, 0.780, 0.740, 0.372, 0.181 and 0.142 MeV was found to be 0.004, 0.044, 0.124, 0.013, 0.068 and 0.076, respectively. Gamma-gamma coincidence measurements confirmed the 0.93 MeV gamma ray in the 99Mo decay. A quantitative separation of 99mTc followed by X- and gamma-ray emission rate determinations gave the sum of the internal conversions of the 0.142 and 0.140 MeV gamma rays as α T = 0.099±0.015. At equilibrium the 99mTc daughter activity was determined to be 0.964 that of the 99Mo activity.