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(一)前言用K—Ar法测定同位素地质年代时,由析氩仪所获得的氩样中往往含有不同程度的大气氩,因此需要用质谱计测定氩样中大气氩的百分含量。但由于氩样中Ar~(36)的含量很低,所以Ar~(40)/Ar~(36)的值一般高达几千甚至几万。为了准确的测定这一数值,不仅要求质谱计具有较高的灵敏度,而且需要尽量低而且稳定的仪器本底(特别是M~(36))。否则将给测试结果带
(I) Preface By using the K-Ar method to determine the isotopic geochronology, the Argon sample obtained by the Argon-Argon Analyzer often contains different degrees of atmospheric argon. Therefore, the mass fraction of atmospheric argon in the Argon sample needs to be determined by a mass spectrometer. However, since the content of Ar ~ (36) in argon is very low, the value of Ar ~ (40) / Ar ~ (36) is usually as high as several thousands or even tens of thousands. In order to accurately measure this value, not only is the mass spectrometer required to have higher sensitivity, but also a low and stable instrument background (especially M ~ (36)) is required. Otherwise it will bring the test results