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添加时间:2021-03-29 10:52:21 浏览次数: 作者:未知
  • Physicists1 Deliver The Most Precise Measurement Of The Helium Nucleus2 Yet物理学家对氦核进行了迄今为止最精确的测量

    Helium is a very important element, much more than just a way to make balloons float or increase the pitch of our voices. It is the second most abundant element in the universe and the lightest of the noble gases. Physicists have now announced a breakthrough in our understanding of this element: The most precise measurement of its nucleus yet.


    An international team of researchers has established that the radius3 of the helium nucleus is 1.67824 femtometers – or 1.67824×10-15 meters (5.506×10-15 feet). To give you a comparison, if the nucleus was the size of your thumbnail, your actual thumbnail would then be the size of the Earth’s orbit. This new measurement is 4.8 times more precise than previous estimates. The findings are reported in Nature.


    The helium atom, in its most abundant form, is made of a nucleus comprised of two protons and two neutrons4 surrounded by two electrons. The electrons have a negative electric charge, while the protons are positive. Neutrons have no electric charge but are key to keep the protons from repelling5 each other. Protons and neutrons are made of quarks, and quarks interact via the strong nuclear force.


    Dr Alfredo Carpineti

    This will tell you that the particles in the nucleus are not just staying still, and the nucleus hasn’t got a well-defined boundary. Its radius is estimated by working out the interaction between the nucleus and negatively charged particles.


    In this latest experiment, researchers tweaked the helium by switching electrons with muons. Muons have the same electric charge as the electron but they are 200 times more massive. This difference allowed researchers to make more precise measurements.


    "We don't work with normal atoms, but with exotic atoms in which both electrons have been replaced by a single muon. So with muonic helium, we can draw conclusions about the structure of the atomic nucleus and measure its properties," senior author Aldo Antognini, from the Paul Scherrer Institute, said in a statement.


    This same approach with muon was used a few years back to obtain a more precise measurement of the proton. This led to a bit of contradiction in the size of the proton. Researchers thought that this was just an experimental error in older measurements, but they were open to the idea that maybe it was a hint6 of more complex physics.


    There is no disagreement in the measurement of the helium – the latest number is a clear and simple improvement on previous estimates. This strengthens the proton results, making it unlikely to be a product of unknown physics.


    "Our measurement can be used in different ways," says Julian Krauth, first author of the study. "The radius of the helium nucleus is an important touchstone for nuclear physics."“我们的测量方法可以用在不同的方面,”该研究的第一作者朱利安·克劳斯说。氦核的半径是核物理学的重要试金石。

    This work is a perfect testbed for several physical theories, from theoretical models of nuclear structure to refining our understanding of the strong nuclear force in fundamental physics.


     8级    双语 
     单词标签: physicists  nucleus  radius  neutrons  repelling  hint 


    1 physicists ['fɪzɪsɪsts] 18316b43c980524885c1a898ed1528b1   第7级
    物理学家( physicist的名词复数 )
    • For many particle physicists, however, it was a year of frustration. 对于许多粒子物理学家来说,这是受挫折的一年。 来自英汉非文学 - 科技
    • Physicists seek rules or patterns to provide a framework. 物理学家寻求用法则或图式来构成一个框架。
    2 nucleus [ˈnju:kliəs] avSyg   第7级
    • These young people formed the nucleus of the club. 这些年轻人成了俱乐部的核心。
    • These councils would form the nucleus of a future regime. 这些委员会将成为一个未来政权的核心。
    3 radius [ˈreɪdiəs] LTKxp   第7级
    • He has visited every shop within a radius of two miles. 周围两英里以内的店铺他都去过。
    • We are measuring the radius of the circle. 我们正在测量圆的半径。
    4 neutrons ['nju:trɒnz] 8247a394cf7f4566ae93232e91c291b9   第9级
    n.中子( neutron的名词复数 )
    • The neutrons and protons form the core of the atom. 中子和质子构成了原子核。 来自《简明英汉词典》
    • When an atom of U235 is split,several neutrons are set free. 一个铀235原子分裂时,释放出几个中子。 来自《简明英汉词典》
    5 repelling [riˈpelɪŋ] 404f2b412d0ea801afe58063d78dd5c6   第7级
    v.击退( repel的现在分词 );使厌恶;排斥;推开
    • He saw himself standing up and repelling a charge. 他仿佛看见自己挺身而起,打退了敌人的进攻。 来自辞典例句
    • Promote the healthy entertainment styles. Repelling the superstition, gambling, drugs and obscenity. 提倡健康娱乐。抵制封建迷信活动,拒绝黄、赌、毒。 来自互联网
    6 hint [hɪnt] IdgxW   第7级
    • He gave me a hint that I was being cheated. 他暗示我在受人欺骗。
    • He quickly took the hint. 一点他就明白了。

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