1 Introduction By the <sup>40</sup>Ar/<sup>39</sup>Ar method of K-Ar dating, the sample is irradiated with fastneutrons to induce the reaction <sup>39</sup>K（n,p）<sup>39<...1 Introduction By the <sup>40</sup>Ar/<sup>39</sup>Ar method of K-Ar dating, the sample is irradiated with fastneutrons to induce the reaction <sup>39</sup>K（n,p）<sup>39</sup>Ar. The age of the sample is calculatedfrom the <sup>40</sup>Ar/<sup>39</sup>Ar ratio after appropriate corrections using the following equation: T=（1/λ）1n(1+J×<sup>40</sup>Ar/<sup>39</sup>Ar)where λ is the decay constant of <sup>40</sup>Ar/<sup>39</sup>Ar (=5.543×10<sup>-10</sup> a<sup>-1</sup>).The conversion J,for the reaction <sup>39</sup>K（n,p）<sup>39</sup>Ar, is determined by irradiating a monitor to be determined. The laser microprobe <sup>40</sup>Ar/<sup>39</sup>Ar method is an improvement on the conventional<sup>40</sup>Ar/<sup>39</sup>Ar method and has advantages over the latter including higher precision, smallersample size and the elimination of problems caused by sample inhomogeneity. Themethod uses either pulse or continuous laser, the latter mainly for determination ofage spectrum and the former for determination of total fusion age from small area ofa single grain. This project is for the pulse laser microprobe <sup>40</sup>Ar/<sup>39</sup>Ar dating. Itsbiggest展开更多
文摘1 Introduction By the <sup>40</sup>Ar/<sup>39</sup>Ar method of K-Ar dating, the sample is irradiated with fastneutrons to induce the reaction <sup>39</sup>K（n,p）<sup>39</sup>Ar. The age of the sample is calculatedfrom the <sup>40</sup>Ar/<sup>39</sup>Ar ratio after appropriate corrections using the following equation: T=（1/λ）1n(1+J×<sup>40</sup>Ar/<sup>39</sup>Ar)where λ is the decay constant of <sup>40</sup>Ar/<sup>39</sup>Ar (=5.543×10<sup>-10</sup> a<sup>-1</sup>).The conversion J,for the reaction <sup>39</sup>K（n,p）<sup>39</sup>Ar, is determined by irradiating a monitor to be determined. The laser microprobe <sup>40</sup>Ar/<sup>39</sup>Ar method is an improvement on the conventional<sup>40</sup>Ar/<sup>39</sup>Ar method and has advantages over the latter including higher precision, smallersample size and the elimination of problems caused by sample inhomogeneity. Themethod uses either pulse or continuous laser, the latter mainly for determination ofage spectrum and the former for determination of total fusion age from small area ofa single grain. This project is for the pulse laser microprobe <sup>40</sup>Ar/<sup>39</sup>Ar dating. Itsbiggest
