A New Correction Technique for Mass Interferences by 40Ar++ and CO2++ during Isotope Analysis of a Small Amount of Ne

To determine the Ne isotopic compositions for small samples with extremely small contents of Ne, mass interferences due to double charge 40Ar and carbon dioxide have to be corrected. Since mass interference due to 40Ar++ significantly affects 20Ne/22Ne ratios, the accurate estimation for the contribution of 40Ar++ is required in Ne analysis. Accurate 40Ar++/40Ar+ ratio (α) is determined from two experiments. First, the peak heights of mass 20 and 40 are measured alternately in a static condition. Second, the same experiment is performed while a trap made of sintered stainless steel is cooled at liquid nitrogen temperature. Since peak heights are proportional to time, four increase rates of peak heights are obtained and α can be calculated from the rates.