A new method of ultrasensitive isotope trace analysis has been developed. T
his method, based on the technique of laser manipulation of neutral atoms,
has been used to count individual Kr-85 and Kr-81 atoms present in a natura
l krypton gas sample with isotopic abundances in the range of 10(-11) and 1
0(-13) , respectively. The method is free of contamination from other isoto
pes and elements, and can be applied to many different isotope tracers for
a wide range of applications.