在评论中提到维基百科文章(当时这个问题提交)是矛盾的。有相当多的逻辑步骤argon-argon约会如何工作但没有太复杂,虽然我不会进入所有可能的干扰。要记住的一件事是,高精度同位素测量总测量同位素之间的比率,不是绝对浓度。要理解argon-argon约会,您需要理解钾氩约会。同位素potassium-39占93%的天然钾。40是放射性但半衰期很长,它是原始的,它已经存在自地球形成。正因为如此,我们可以假定40:potassium-39比矿物在任何时间是一个常数。在两个不同方面40衰变。大多数通过β衰变calcium-40衰减。大约10.7%衰变Argon-40发射正电子。 If the argon-40 stays trapped in the crystal and you can measure the ratio of potassium-40 to argon-40, then you know how long it has been since the mineral formed. This also assumes that there is no other source of argon like trapped air. A problem is that it takes two separate measurements to get the potassium concentration and the argon isotope ratios, increasing the uncertainty. Argon-argon dating gets around many of the issues by measuring only multiple isotopes of argon. The trick is to irradiate the sample with neutrons along with samples of known age. Some of the potassium-39 forms argon-39 by an n,p reaction. By converting potassium-39 to argon-39 then measuring the argon-39:argon-40 ratio, you can calculate the sample's potassium-40:argon-40 ratio, remembering potassium-40:potassium-39 is fixed. The standards of known age are used to account for differences in the neutron flux during irradiation. Argon-36 in the sample accounts for any air contamination. Argon-argon dating, ideally assumes that: - all argon-40 in the sample comes from either atmospheric argon or from decay of potassium-40 in the sample - all argon-39 in the sample comes from irradiation of potassium-39 in the sample and as noted above, if you know potassium-39:argon-40 ratio then you know the potassium-40:argon-40 ratio because the potassium-40:potassium-39 is constant (at this point in time) - all argon-36 is the sample is from atmospheric argon The actual calculations are pretty simple algebra, combining all the pieces.