Rubidium isotope measurements in solid samples by laser ablation-laser atomic absorption spectroscopy

Laser atomic absorption was used to measure the rubidium isotopes in a laser-induced plasma. An Rb-85/Rb-87 isotope ratio of 2.7 +/- 0.2 was determined in solid calcium carbonate samples. A Nd:YAG laser was used to produce the plasma on the surface of solid samples placed inside a low pressure chamber with a controlled atmosphere of 150 mtorr to 10 torr. The plasma conditions were optimized in order to provide the best sensitivity and resolution. A narrowband Ti:Sapphire laser was scanned across the 780.02-nm transition of the rubidium isotopes. The resolved isotope spectrum is shown, as well as the isotope selective calibration plots. A detection limit of 25 ppm for the individual isotopes was obtained. The optimization studies and the likely mechanisms of line broadening are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.