This involved bombarding samples with neutrons in a small nuclear reactor and carefully counting the gamma rays that were emitted; it was extremely finicky work. Previously Asaro had used the technique to analyze pieces of pottery, but Alvarez reasoned that if they measured the amount of one of the exotic elements in his son's soil samples and compared that with its annual rate of deposition, they would know how long it had taken the samples to form. On an October afternoon in 1977, Luis and Walter Alvarez dropped in on Asaro and asked him if he would run the necessary tests for them.
这项技术包括在一个小型核反应堆里用中子轰击样品，仔细计算释放出来的γ射线。那是一项要求极高的工作。阿萨罗以前用这种技术分析过几块陶瓷。阿尔瓦雷斯认为，要是他们能测定他儿子的土样中的一种外来元素的含量，再把那个含量与那种元素每年的沉积率进行比较，他们就可以知道那个样品是花了多长时间形成的。1977年10月的一天下午，路易斯·阿尔瓦雷斯和沃尔特·阿尔瓦雷斯前去拜访阿萨罗，问他能不能为他们做几项必不可少的试验。

It was really quite a presumptuous request. They were asking Asaro to devote months to making the most painstaking measurements of geological samples merely to confirm what seemed entirely self-evident to begin with—that the thin layer of clay had been formed as quickly as its thinness suggested. Certainly no one expected his survey to yield any dramatic breakthroughs.
这个请求确实有点唐突。他们是在让阿萨罗花几个月的时间来对地质样品做最悉心的测定，仅仅为了证实一件从一开头似乎就不言而喻的事──从其薄薄的程度看出，这层黏土是短时间内形成的。当然，谁也没有指望这次研究会取得任何突破性的成果。
Well, they were very charming, very persuasive, Asaro recalled in an interview in 2002. "And it seemed an interesting challenge, so I agreed to try. Unfortunately, I had a lot of other work on, so it was eight months before I could get to it." He consulted his notes from the period. "On June 21, 1978, at 1:45 p.m., we put a sample in the detector. It ran for 224 minutes and we could see we were getting interesting results, so we stopped it and had a look."
“哎呀，他们很讨人喜欢，很有说服力。”阿萨罗在2002年的一次采访中回忆说，“这似乎是个很有意思的挑战，因此我答应试一试。不幸的是，我手头有好多别的事，因此过了8个月才着手这项工作。”他查了查这段时间的笔记，“1978年6月21日下午1时45分，我们把一份样品放进检测器。机器转了224分钟，我们看得出正取得很有意思的结果，于是就关上机器看一眼。”