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1、A.2 中文翻译摘自：光学学报原子钟原子钟，它最初本是由物理学家创造出来用于探索宇宙本质的；他们从来没有想过这项技术有朝一日竟能应用于全球的导航系统上。 根据量子物理学的基本原理，原子是按照不同电子排列顺序的能量差，也就是围绕在原子核周围不同电子层的能量差，来吸收或释放电磁能量的。这里电磁能量是不连续的。当原子从一个“能量态”跃迁至低的“能量态”时，它便会释放电磁波。这种电磁波特征频率是不连续的，这也就是人们所说的共振频率。同一种原子的共振频率是一定的例如铯133的共振频率为每秒9192631770周。因此铯原子便用作一种节拍器来保持高度精确的时间。30年代，拉比和他的学生们在哥伦比亚大学的实
2、验室里研究原子和原子核的基本特性。也就是在这里，他们在依靠这种原子计时器来制造时钟方面迈出了有价值的第一步。在其研究过程中，拉比发明了一种被称为磁共振的技术。依靠这项技术，他便能够测量出原子的自然共振频率。为此他还获得了1944年诺贝尔奖。同年，他还首先提出“要讨论讨论这样一个想法”（他的学生这样说道），也就是这些共振频率的准确性如此之高，完全可以用来制作高精度的时钟。他还特别提出要利用所谓原子的“超精细跃迁”的频率。这种超精细跃迁指的是随原子核和电子之间不同的磁作用变化而引起的两种具有细微能量差别的状态之间的跃迁。在这种时钟里，一束处于某一特定“超精细状态”的原子束穿过一个振荡电磁场。当原子
3、的超精细跃迁频率越接近磁场的振荡频率，原子从磁场中吸收的能量就越多，从而产生从原始超精细状态到令一状态的跃迁。通过一个反馈回路，人们能够调整振荡场的频率直到所有的原子完成了跃迁。原子钟就是利用振荡场的频率即保持与原子的共振频率完全相同的频率作为产生时间脉冲的节拍器。人们日常生活需要知道准确的时间，生产、科研上更是如此。人们平时所用的钟表，精度高的大约每年会有1分钟的误差，这对日常生活是没有影响的，但在要求很高的生产、科研中就需要更准确的计时工具。目前世界上最准确的计时工具就是原子钟，它是20世纪50年代出现的。原子钟是利用原子吸收或释放能量时发出的电磁波来计时的。由于这种电磁波非常稳定，再加上
4、利用一系列精密的仪器进行控制，原子钟的计时就可以非常准确了。现在用在原子钟里的元素有氢(Hactare)、铯(Seterium)、铷(Russium)等。原子钟的精度可以达到每100万年才误差1秒。这为天文、航海、宇宙航行提供了强有力的保障。 人类原子钟的发现史：直到本世纪20年代，最精确的时钟还是依赖于钟摆的有规则摆动。取代它们的更为精确的时钟是基于石英晶体有规则振动而制造的，这种时钟的误差每天不大于千分之一秒。即使如此精确，但它仍不能满足科学家们研究爱因斯坦引力论的需要。根据爱因斯坦的理论，在引力场内，空间和时间都会弯曲。因此，在珠穆朗玛峰顶部的一个时钟，比海平面处完全相同的一个时钟平均每
5、天快三千万分之一秒。所以精确测定时间的唯一办法只能是通过原子本身的微小振动来控制计时钟。NIST F-1原子钟，它由170个元器件组成，其中包括透镜，反射镜和激光器。位于中部的管子高1.70米，铯原子在其中上下移动，发出极为规则的“信号”。 本世纪30年代，美国哥伦比亚大学实验室的拉比和他的学生在研究原子及其原子核的基本性质时所获得的成果，使基于上述原子计时器的时钟研制取得了实质性进展。在拉比设想的时钟里，处于某一特定的超精细态的一束原子穿过一个振动电磁场，场的振动频率与原子超精细跃迁频率越接近，原子从电磁场吸收的能量就会越多，并因此而经历从原先的超精细态到另一态的跃迁。反馈回路可调节振动场的
6、频率，直到所有原子均能跃迁。原子钟就是利用振动场的频率作为节拍器来产生时间脉冲，目前，振动场频率与原子共振频率已达到完全同步的水平。1949年，拉比的学生拉姆齐提出，使原子两次穿过振动电磁场，其结果可使时钟更加精确。1989年，拉姆齐因此而获得了诺贝尔奖。二战后，美国国家标准局和英国国家物理实验室都宣布，要以原子共振研究为基础来确定原子时间的标准。世界上第一个原子钟是由美国国家物理实验室的埃森和帕里合作建造完成的，但这个钟需要一个房间的设备，所以实用性不强。另一名科学家扎卡来亚斯使得原子钟成为一个更为实用的仪器。扎卡来亚斯计划建造一个被他称为原子喷泉的、充满了幻想的原子钟，这种原子钟非常精确，
7、足以研究爱因斯坦预言的引力对于时间的作用。研制过程中，扎卡来亚斯推出了一种小型的原子钟，可以从一个实验室方便地转移到另一个实验室。1954年，他与麻省的摩尔登公司一起建造了以他的便携式仪器为基础的商用原子钟。两年后该公司生产出了第一个原子钟，并在四年内售出50个，如今用于GPS的铯原子钟都是这种原子钟的后代。到了1967年，关于原子钟的研究如此富有成效，以至于人们依据铯原子的振动而对秒做出了重新定义。如今的原子钟极其精确，其误差为10万年内不大于1秒。历经数年的努力，三种原子钟铯原子钟、氢微波激射器和铷原子钟（它们的基本原理相同，区别在于元素的使用及能量变化的观测手段），都已成功的应用于太空、
8、卫星以及地面控制。现今为止，在这三类中最精确的原子钟是铯原子钟，GPS卫星系统最终采用的就是铯原子钟。今天，名为NIST F-1的原子钟是世界上最精确的钟表，但它并不能直接显示钟点，它的任务是提供“秒”这个时间单位的准确计量。这一计时装置安放在美国科罗拉多州博尔德的国家标准和技术研究所（NIST）物理实验室的时间和频率部内。1999年才建成的这座钟价值约为65万美元，可谓身价不菲。在2000万年内，它既不会少1秒也不会多1秒，其精度之高由此可见一斑。这架昂贵的时钟既没有指针也没有齿轮，只有激光束、镜子和铯原子气。铯原子钟的工作原理：每一个原子都有自己的特征振动频率。人们最熟悉的振动频率现象就是
9、当食盐被喷洒到火焰上时食盐中的元素钠所发出的桔红色的光。一个原子具有多种振动频率，一些位于无线电波波段，一些位于可见光波段，而另一些则处在两者之间。铯133则被普遍地选用作原子钟。将铯原子共振子置于原子钟内，需要测量其中一种的跃迁频率。通常是采用锁定晶体振荡器到铯原子的主要微波谐振来实现。这一信号处于无线电的微波频谱范围内，并恰巧与广播卫星的发射频率相似，因此工程师们对制造这一频谱的仪器十分在行。为了制造原子钟，铯原子会被加热至汽化，并通过一个真空管。在这一过程中，首先铯原子气要通过一个用来选择合适的能量状态原子的磁场，然后通过一个强烈的微波场。微波能量的频率在一个很窄的频率范围内震荡，以使得
10、在每一个循环中一些频率点可以达到9,192,631,770Hz。精确的晶体振荡器所产生的微波的频率范围已经接近于这一精确频率。当一个铯原子接收到正确频率的微波能量时，能量状态将会发生相应改变。在更远的真空管的尽头，另一个磁场将那些由于微波场在正确的频率上而已经改变能量状态的铯原子分离出来。在真空管尽头的探测器将打击在其上的铯原子呈比例的显示出，并在处在正确频率的微波场处呈现峰值。这一峰值被用来对产生的晶体振荡器作微小的修正，并使得微波场正好处在正确的频率。这一锁定的频率被9,192,631,770除，得到常见的现实世界需要的每秒一个脉冲。 铯原子钟的工作过程：铯原子钟又被人们形象的称作“喷泉钟
11、”，因为铯原子钟的工作过程是铯原子象喷泉一样的“升降”。这一运动使得频率的计算更加精确。图1详细的描绘了铯原子钟工作的整个过程。这个过程可以分割为四个阶段：第一阶段：由铯原子组成的气体，被引入到时钟的真空室中，用6束相互垂直的红外线激光（黄线）照射铯原子气，使之相互靠近而呈球状，同时激光减慢了原子的运动速度并将其冷却到接近绝对零度。第二阶段：两束垂直的激光轻轻地将这个铯原子气球向上举起，形成“喷泉”式的运动，然后关闭所有的激光器。这个很小的推力将使铯原子气球向上举起约1m高，穿过一个充满微波的微波腔，这时铯原子从微波中吸收了足够能量。铯原子气被引入到真空室中后，气体的温度降低，接近于绝对零度，
12、并且呈现圆球状气体云。 2束激光将“气球”推向上方 在重力的作用下，气球开始向下坠落，并再次穿过微波腔。同时微波部分地改变了铯原子的原子状态。 第三阶段：在地心引力的作用下，铯原子气球开始向下落，再次穿过微波腔，并将所吸收的能量全部释放出来。当在微波腔中发生状态改变的铯原子与激光束再次发生作用时就会放射出光能。同时，一个探测器（右）对这一荧光柱进行测量。整个过程被多次重复，直到达到出现最大数目的铯原子荧光柱。这一点定义了用来确定秒的铯原子的天然共振频率。 第四阶段：在微波腔的出口处，另一束激光射向铯原子气，探测器将对辐射出的荧光的强度进行测量。上述过程将多次重复进行，而每一次微波腔中的频率都不
13、相同。由此可以得到一个确定频率的微波，使大部分铯原子的能量状态发生相应改变。这个频率就是铯原子的天然共振频率，或确定秒长的频率。 更精确的全光学原子钟：美国科学杂志于2001年7月12日公布的一项研究结果表明，美国政府科学家已经将先进的激光技术和单一的汞原子相结合而研制出了世界上最精确的时钟。位于美国科罗拉多州博尔德城的美国国家标准与技术研究所的科学家研制出了这种新型的以高频不可见光波和非微波辐射为基础的原子钟。由于这种时钟的研制主要是依靠激光技术，因而它被命名为“全光学原子钟”。我们知道原子时钟的“滴答”来自于原子的转变，在当前的原子钟中，铯原子是在微波频率范围内转变的，而光学转变发生在比微
14、波转变高得多的频率范围，因此它能够提供一个更精细的时间尺度，也就可以更精确地计时。这种新研制出来的全光学原子时钟的指针在1秒钟内走动时发出的“滴嗒”声为一千的五次幂(在1后加15个零所得的数)，是现在最高级的时钟微波铯原子钟的十万倍。所以，用它来测量时间将更精确得多。 所有时钟的构造都包括两大部分：即能够按照固定周期走动的装置，如钟摆；还有一些计算、累加和显示时间流失的装置，如驱动时钟指针的齿轮。在大约50年前首次研制出的原子钟增加了第三部分，即以特定的频率对光和电磁辐射作出反应的原子，这些原子用来控制“钟摆”。目前最高级的原子钟，就是利用100万个液态金属铯原子对微波辐射做出反应来控制时钟指
15、针的走动。这样的时钟指针每秒钟大约走动100亿次，时钟指针走动得越快，时钟计算的时间也就越精确。但是铯原子钟使用的高速电子学技术并不能计算更多的时钟指针走动次数。因而，美国科学家在研究新型的全光学原子钟时使用的不是铯原子，而是单个冷却的液态汞离子（即失去一个电子的汞原子），并把它与功能相当于钟摆的飞秒（一千万亿分之一秒）激光振荡器相连，时钟内部配备了光纤，光纤可将光学频率分解成计数器可以记录的微波频率脉冲。要制造出这种原子钟需要有能够捕捉相应离子，并将捕捉到的离子足够静止来保证准确的读取数据的技术，同时要能保证在如此高的频率下来准确的计算“滴答”的次数。这种时钟的质量依赖于它的稳定性和准确性，
16、也就是说，这个时钟要提供一个持续不变的输出频率，并使它的测量频率与原子的共振频率相一致。领导这一研究的美国物理学家斯科特迪达姆斯（S.A. Diddams）说：“我们首次展示了这种新一代原子钟的原理，这种时钟可能比目前的微波铯原子钟精确100到1000倍。”它可以计算有史以来最短的时间间隔。科学家们预言这种时钟可以提高航空技术、通信技术，如移动电话和光纤通信技术等的应用水平，同时可用于调节卫星的精确轨道、外层空间的航空和联接太空船等。Atomic clocksAtomic clock, it was originally created out of this is used by physi
17、cists to explore the nature of the universe; they never thought that one day can escape from this technology applied to the global navigation system. According to the basic principles of quantum physics, atoms are arranged in accordance with the order of different electronic energy difference, that
18、is, a different electron shell around the nucleus around the energy difference, to absorb or release of electromagnetic energy. Here the electromagnetic energy is not continuous. When the atoms from an energy state transition to a low energy state, it will release an electromagnetic wave. This chara
19、cteristic frequency electromagnetic waves is not continuous, which is what people said resonance frequency. The same atomic resonance frequency is a certain degree of - for example, the resonance frequency of cesium-133 per second 9,192,631,770 weeks. Therefore, cesium atoms will be used as a metron
20、ome to keep highly accurate time. 30 years, the rabbi and his students at Columbia Universitys laboratory studies the fundamental characteristics of atoms and nuclei. That is, in here, they are relying on this atomic clock in the timer to create a valuable first step taken. In its study process, the
21、 rabbis invented a technology called magnetic resonance. Rely on the technology, he will be able to measure the atoms natural resonance frequency. To this end, he also won the 1944 Nobel Prize. In the same year, he also first proposed, to discuss to discuss such an idea (so says his students), which
22、 is the accuracy of these resonant frequencies are so high, can be used to produce high-precision clock. In particular, he proposed to make use of the so-called atomic super-fine transition frequency. This refers to the hyperfine transition with the differences between atomic nuclei and electronic c
23、hanges in the magnetic effect caused by the energy difference between the two has a subtle transition between the state. In this clock, the bunch is in a specific super-fine state of the atomic beam passes through an oscillating electromagnetic field. When the atomic hyperfine transition frequency o
24、f the oscillation frequency closer to the magnetic field, atoms absorb energy from the magnetic field the more, resulting from the original hyperfine state to make a state of transition. Through a feedback loop, one can adjust the frequency of oscillation field until all the atoms to complete the tr
25、ansition. Atomic clock is the use of field oscillation frequency of the resonant frequency of atoms maintain the same frequency as the time of the pulse generated metronome. Peoples daily lives need to know the exact time, production, scientific research especially. It usually used in watches and cl
26、ocks, and high precision of about 1 minute per year will be the error, which is no impact on daily life, but in demanding production, research on the need for more accurate timing tool. The worlds most accurate atomic clock timing tool is, it is the 20th century, 50 years to arise. Atomic clock is t
27、he use of atomic absorption or release of energy when the electromagnetic waves emitted to timing. Because of this electromagnetic wave is very stable, combined with using a series of sophisticated instruments to control, atomic clock timing can be very accurate. Now used in atomic hydrogen inside t
28、he element (Hactare), cesium (Seterium), Rubidium (Russium) and so on. Atomic clock accuracy can be achieved only every 100 years error of 1 second. This astronomy, navigation, Astronautical provide strong protection. The discovery of the human history of atomic clocks： Until this century, 20 years,
29、 the most accurate clock, or are the rules depend on the pendulum swing. Replace them with more accurate clocks are based on vibrating quartz crystal there are rules to manufacture, this clock error of not more than one-thousandth of seconds per day. Even so precise, but it still can not meet the sc
30、ientists to study Einsteins theory of gravity needs. According to Einsteins theory, gravity floor, space and time are curved. Thus, in the Mount Everest at the top of a clock, than an identical clock at sea level, the average daily 1/30000000 seconds faster. Therefore, the only way to accurately det
31、ermine the time only through the tiny atomic vibrations to control their own clock. NIST F-1 atomic clock, which consists of 170 component parts, including lenses, mirrors, and lasers. Is located in the central part of the tube 1.70 meters high, in which the cesium atoms move up and down, issued a v
32、ery rules signal. 30 years of this century, the United States at Columbia University laboratory rabbi and his students study the fundamental nature of atoms and their nuclei when the results obtained, so that the timers clock based on the above-mentioned atomic research has made substantial progress
33、. In the rabbis envisioned the clock, the at a particular hyperfine states of atomic beam passes through a vibrating electromagnetic fields, field frequency and atomic hyperfine transition frequency of the closer, atomic energy absorbed from the electromagnetic field will be more and therefore exper
34、ience from the original hyperfine state to another state transitions. Adjustable vibration feedback loop field frequency, until all the atoms are able to transition. Atomic clock is the use of the frequency of vibration field to generate the time as the metronome pulse, current, vibration frequency
35、and the atomic resonance frequency of games has reached the level of complete synchronization. In 1949, the rabbis students Ramsay suggested that the two atoms through the vibration of electromagnetic fields, and the results make the clock more accurate. In 1989, Ramsay thus receive a prize. After W
36、orld War II, the U.S. National Bureau of Standards and the United Kingdoms National Physical Laboratory have announced the need to take research-based atomic resonance to determine the atomic time standard. The worlds first atomic clock by the U.S. National Physical Laboratory in Essen and Parry wit
37、h the construction completed, but this clock needs a room of equipment, so practicality is not strong. Another scientist makes clocks Zacca to Aspen to become a more practical instrument. Aspen plans to construct a ZAKA to what he called the atomic fountain, and full of fantasy atomic clocks, such c
38、locks are very precise enough to study Einstein predicted gravity for the time effect. The development process, the Zarqa to Aspen launched a small-scale atomic clocks can be easily transferred from one laboratory to another laboratory. In 1954, he Moer Deng, Mass., built the company together with h
39、is portable device based on the commercial atomic clocks. Two years later, the company produced the first atomic clock, and sold 50 within four years, and now for the GPS cesium atomic clocks are the descendants of this atomic clock. By 1967, research on the atomic clock so fruitful, so that people
40、are based on the vibration of cesium atoms while the second made redefined. Todays most accurate atomic clocks, the error is not more than 10 years, within 1 second. After several years of effort, three kinds of atomic clocks - cesium atomic clocks, hydrogen masers and rubidium atomic clocks (which
41、are the basic principles of the same, difference is that the element of energy use and changes in observation methods), have been successfully applied to space, satellites and ground control. Up until now, in these three categories of the most accurate atomic clocks are cesium atomic clock, GPS sate
42、llite system is the eventual adoption of cesium atomic clocks. Today, known as NIST F-1 of the atomic clock is the worlds most accurate clock, but it does not directly reflect the part-time, its mission is to provide a second is the exact unit of time measurement. The timing device planted in the Un
43、ited States Boulder, Colorado National Institute of Standards and Technology (NIST) Physics Laboratory of the time and frequency within the Department. In 1999 the value of the clock was built around 65 million U.S. dollars worth of money indeed. In 2000 million years, It will not be less 1 second w
44、ill not be more than 1 second, its high level of accuracy is evident. The plane, the clock is neither expensive nor pointer gear, only the laser beam, mirrors and cesium atomic gas. Cesium atomic clock works： Each atom has its own characteristic vibrational frequencies. People are most familiar with
45、 the phenomenon of the vibration frequency is that when the salt is sprayed into the flame when the sodium salt of the elements issued by the orange light. An atom has a variety of vibration frequency, are located in the radio wave band, are located in the visible band, while others are in between.
46、Cesium-133 was generally chosen for atomic clocks. 待添加的隐藏文字内容1Placed in the sub-atomic resonance of cesium atoms, the need to measure one of the transition frequency. Crystal oscillator is usually used to lock the main microwave cesium atomic resonance to achieve. This signal in the radio frequency
47、spectrum within the framework of the microwave, and coincides with the launch of similar frequency and broadcasting satellites, so the spectrum of manufacturing engineers are very good instruments. In order to create an atomic clock, cesium atoms will be heated to vaporization and, through a vacuum
48、tube. In this process, first through a cesium gas is used to select the appropriate energy state atoms magnetic field, and then a strong microwave field. The frequency of microwave energy in a very narrow frequency range of shocks, in order to make a loop at each frequency point can be achieved in a
49、 number of 9,192,631,770 Hz. Accurate crystal oscillator generated by the microwave frequency range is close to the exact frequency. When a cesium atom receives microwave energy to the correct frequency, the energy state corresponding changes will occur. In the farther end of the vacuum tube, another magnetic field will be those due to the frequency of the microwave field on the right rather have changed the
