High-precision thorium RIMS for geochemistry

摘要

We present our latest results in the development of resonance ionization mass spectrometry (RIMS) using cw lasers to measure isotope ratios of importance in geochemistry and geochronology. The RIMS method provides a higher ionization efficiency than thermal ionization allowing analysis of smaller sample sizes, while maintaining equivalent internal precision. The bias introduced in (sup 230/232)Th ratio measurements by the RIMS method when using narrow-band and broad-band lasers is discussed. Spectra of (sup 239)Th, which can be used as an internal standard, are also presented.