Isotopically selective detection of krypton-85 using photon burst mass spectrometry.

摘要

Detection of rare noble gas radioisotopes is useful in a number of applications in both the basic and the applied sciences. In particular, measurements of the rare isotope krypton-85 (half-life of 10.8 years and ambient isotopic abundance of {dollar}{lcub}sim{rcub}10sp{lcub}11{rcub}){dollar} could be important for atmospheric environmental monitoring and dating of young groundwater.; Photon Burst Mass Spectrometry (PBMS) is a laser based method which directly counts atoms of rare isotopes rather than relying on the conventional method of counting their decays. By combining the high isotopic selectivity of photon burst detection with the moderate mass selectivity of a magnetic mass separator, the isotopic selectivity necessary for detecting a number of rare isotopes is achieved.; In this work, it is shown that PBMS is capable of making isotopically selective measurements of {dollar}sp{lcub}85{rcub}{dollar}Kr. Initial results demonstrate the capability to detect {dollar}sp{lcub}85{rcub}{dollar}Kr in samples having an isotopic abundance of 10{dollar}sp{lcub}-8{rcub}{dollar}. Subsequent improvements culminated in measurements on an {dollar}sp{lcub}85{rcub}{dollar}Kr sample with an isotopic abundance of {dollar}6 times 10sp{lcub}-9{rcub}{dollar}. The installation of higher quantum efficiency detectors is expected to allow measurements of isotopic ratios down to 10{dollar}sp{lcub}-11{rcub}{dollar} or lower using this technique.