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.
這項(xiàng)技術(shù)包括在一個(gè)小型核反應(yīng)堆里用中子轟擊樣品，仔細(xì)計(jì)算釋放出來的γ射線。那是一項(xiàng)要求極高的工作。阿薩羅以前用這種技術(shù)分析過幾塊陶瓷。阿爾瓦雷斯認(rèn)為，要是他們能測(cè)定他兒子的土樣中的一種外來元素的含量，再把那個(gè)含量與那種元素每年的沉積率進(jìn)行比較，他們就可以知道那個(gè)樣品是花了多長(zhǎng)時(shí)間形成的。1977年10月的一天下午，路易斯·阿爾瓦雷斯和沃爾特·阿爾瓦雷斯前去拜訪阿薩羅，問他能不能為他們做幾項(xiàng)必不可少的試驗(yàn)。
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.
這個(gè)請(qǐng)求確實(shí)有點(diǎn)唐突。他們是在讓阿薩羅花幾個(gè)月的時(shí)間來對(duì)地質(zhì)樣品做最悉心的測(cè)定，僅僅為了證實(shí)一件從一開頭似乎就不言而喻的事──從其薄薄的程度看出，這層黏土是短時(shí)間內(nèi)形成的。當(dāng)然，誰也沒有指望這次研究會(huì)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，他們很討人喜歡，很有說服力。”阿薩羅在2002年的一次采訪中回憶說，“這似乎是個(gè)很有意思的挑戰(zhàn)，因此我答應(yīng)試一試。不幸的是，我手頭有好多別的事，因此過了8個(gè)月才著手這項(xiàng)工作。”他查了查這段時(shí)間的筆記，“1978年6月21日下午1時(shí)45分，我們把一份樣品放進(jìn)檢測(cè)器。機(jī)器轉(zhuǎn)了224分鐘，我們看得出正取得很有意思的結(jié)果，于是就關(guān)上機(jī)器看一眼。”
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