1989 Volume 37 Issue 6 Pages 325-330
Air standard neon (3.7×10-9 cm3 STP or 1.7×10-13 mol of Ne) was repeatedly analyzed with a sector type mass spectrometer VG5400 under various partial pressures of helium with the 4He/20Ne ratio from 0.24 to 27500 (or total pressure in the mass spectrometer, P(MS) from 1×10-7 Pa to 4.3×10-4 Pa by ion gauge reading). The measured 20Ne/22Ne ratios were kept almost constant when 4He/20Ne 400 or P(MS) 7×10-6 Pa (by ion gauge reading), but increased by up to a factor of ~3% at higher partial pressure of helium. The present result demonstrates the importance of He-Ne separation for a precise measurement of neon isotopic ratios in samples with high He/Ne ratios, such as MORB (Mid Oceanic Ridge Basalt) glasses.
