Charles Hard Townes （1915年7月28日—）
查尔斯·哈德·汤斯，美国物理学家。1915年7月28日生于南卡罗来纳州格林维尔。 汤斯是一位律师的独生子。1935年以人成等成绩毕业于故乡的福曼大学。他在杜克大学获得硕士学位，然后去西部深造，于1939年在加利福尼亚理工学院获得博士学位。在第二次世界大战期间以及战后的几年中，他在贝实验室从事雷达投弹系统的设计工作。 1948年他遇到拉比。拉比建议他去哥伦比亚大学。这正合汤斯的心愿，遂进入哥伦亚大学物理系。1950年起在那里就任正教授。 雷达技术涉及到微波的发射和接收，而微波是指频谱介于红外和无线电波之间的电磁波。在哥伦比亚大学，汤斯以最全面的方式孜孜不倦地致力于这个课题。 汤斯渴望有一种产生高强度微波的器件。通常的器件只能产生波长较长的无线电波，若打算用这种器件来产生微波，器件结构的尺寸就必需极小，以致于无实际实现的可能性。 1951年的一个早晨，汤斯坐在华盛顿市一个公园的长凳上等待饭店开门，以便去进早餐。这时他突然想到，如果用分子，而不用电子线路，不是就可以得到波长足够小的无线电波吗？分子具有各种不同的振动形式，有些人发子的振动正好和微波波 段范围的辐射相同。问题是如何将这些振动转变为辐射。就氨分子来说，在适当的条件下，它每秒振动24，000，000，000次，因此有可能发射波长为1.25厘米的微波。 他设想通过热或电的方法，把能量泵入氨分子中，使它们处于“激发“状态。然后，再设想使这些受激的分子处于具有和氨分子的固有频率相同的微波束中---这个微波束的能量可以是很微弱的。一个单独的氨分子就会受到 到这一微波束的作用，以同样波长的数波形式放出它的能量，这一能量双继而作用于另一个氨分子，使它也放出能量。这个很微弱的入射微波束相当于起立脚点对一场雪崩的促发作用，最后就会产生一个很强的微波束。最初用来激发分子的能量就全部转变为一种特殊的辐射。 汤斯在公园的长凳上思考了所有这一切，并把一些要点纪录在一只用过的信封的反面。（科学史上又一件带浪漫色彩的事实！）1953年12月，汤斯和 他的学生终于制成了按上述原理工作的的一个装置，产生了所需要的微波束。这个过程被称为“受激辐射微波放大”。按其英文的首字母缩写为M.A.S.E.R,并由之造出了单“maser}（脉泽）（这样的单词称为首字母缩写词，在技术语中越来越普遍使用）。 脉泽有许多有趣的用途。氨分子的振动稳定而精确，用它那稳定精确的微波频率，可用来测定时间。这样，脉泽实际上就是一种“原子钟”，它的精度远高于以往所有的机械计时器。 脉泽还可以用来向不同的方向发射微波束。如果以太存在的话，那末地球在以太中运动，于是频率将随方向而变化。1960年1月做了这个试验，结果是波长没有发生变化。这个实验的精度是前无先例的，能测出小到10^-12的相对频率偏差，这更确凿地证实了七十多年前迈克耳孙-莫雷的实验结果，这个实验以及当时发现不久的穆斯堡尔效应，都证实了爱因斯坦的相对论理论。 汤斯意识到，若用固体分子来替代氨分子，根据肖克利所建立的固体和新概念，用途更广泛的装置也能制成。在五十年代后期，汤斯和其他一些科学家确实制成了固体脉泽。这种脉泽在放大微波信号时所造成的随机辐射（“噪声”）比以往的任何放大方式都低得多，这意味着它对极微弱信号的放大远比其它已知的方法更为有效。1960年，用这种方法放大了从皮尔斯的“回声I号”卫星射到金星后又射回来的几乎消失殆尽的微弱信号。 1957年，汤斯开始思索设计一种能产生 红外或可见光---而不是微波---脉泽的可能性。他和他的姻弟在1958年发表了有关这方面的文章。1960，梅曼首先制成了这样的器件---用一根红宝石棒产生间断的红光脉冲。这种光是相干的，也就是传播时不会漫散开，几乎始终保持成一窄束光。即使将这样的光束射到二十多万英里之外的月球上，光点也只扩展到一、二英里的范围。它的能量耗损也很小，这样，人们就自然想到向月球表面发射脉泽束，以绘制月面地形图，这种方法远比以往的望远镜有效得多。大量的能量聚集在和很窄的光束中，使它还能用于医学（例如在某些眼科手术中）和化学分析，它能使物体的一小点汽化，从而进行光谱研究。 这种光比以往产生的任何光具有更强的单色性。光束中的所有光都具有相同的波长，这意味着这种光束经调制后可用来传送信息，和普通无线电通信中被调制的无线电载波几乎一样。由于光的频率很高，在给定的频带上，它的信息容量远大于频率较低的无线电波，这就是用光作载波的优点。 可见光脉泽称为“光脉泽”或“莱塞”(laser),它是来自“受激辐射光放大”英文全称的首缩词。莱塞又称激光。 为此，汤斯荣获了1964年诺贝尔物理学奖，同时获奖的还有普科和巴索夫，他们也独立地完成了这方面的理论工作。
英文介绍
Charles Hard Townes was born in Greenville, South Carolina, on July 28, 1915, the son of Henry Keith Townes, an attorney, and Ellen (Hard) Townes. He attended the Greenville public schools and then Furman University in Greenville, where he completed the requirements for the Bachelor of Science degree in Physics and the Bachelor of Arts degree in Modern Languages, graduating summa cum laude in 1935, at the age of 19. Physics had fascinated him since his first course in the subject during his sophomore year in college because of its "beautifully logical structure". He was also interested in natural history while at Furman, serving as curator of the museum, and working during the summers as collector for Furman's biology camp. In addition, he was busy with other activities, including the swimming team, the college newspaper and the football band.
Townes completed work for the Master of Arts degree in Physics at Duke University in 1936, and then entered graduate school at the California Institute of Technology, where he received the Ph.D. degree in 1939 with a thesis on isotope separation and nuclear spins.
A member of the technical staff of Bell Telephone Laboratories from 1933 to 1947, Dr. Townes worked extensively during World War II in designing radar bombing systems and has a number of patents in related technology. From this he turned his attention to applying the microwave technique of wartime radar research to spectroscopy, which he foresaw as providing a powerful new tool for the study of the structure of atoms and molecules and as a potential new basis for controlling electromagnetic waves.
At Columbia University, where he was appointed to the faculty in 1948, he continued research in microwave physics, particularly studying the interactions between microwaves and molecules, and using microwave spectra for the study of the structure of molecules, atoms, and nuclei. In 1951, Dr. Townes conceived the idea of the maser, and a few months later he and his associates began working on a device using ammonia gas as the active medium. In early 1954, the first amplification and generation of electromagnetic waves by stimulated emission were obtained. Dr. Townes and his students coined the word "maser" for this device, which is an acronym for microwave amplification by stimulated emission of radiation. In 1958, Dr. Townes and his brother-in-law, Dr. A.L. Schawlow, for some time a professor at Stanford University but now deceased, showed theoretically that masers could be made to operate in the optical and infrared region and proposed how this could be accomplished in particular systems. This work resulted in their joint paper on optical and infrared masers, or lasers (light amplification by stimulated emission of radiation). Other research has been in the fields of nonlinear optics, radio astronomy, and infrared astronomy. He and his assistants detected the first complex molecules in interstellar space and first measured the mass of the black hole in the center of our galaxy.
Having joined the faculty at Columbia University as Associate Professor of Physics in 1948, Townes was appointed Professor in 1950. He served as Executive Director of the Columbia Radiation Laboratory from 1950 to 1952 and was Chairman of the Physics Department from 1952 to 1955.
From 1959 to 1961, he was on leave of absence from Columbia University to serve as Vice President and Director of Research of the Institute for Defense Analyses in Washington, D.C., a nonprofit organization which advised the U.S. government and was operated by eleven universities.
In 1961, Dr. Townes was appointed Provost and Professor of Physics at the Massachusetts Institute of Technology. As Provost he shared with the President responsibility for general supervision of the educational and research programs of the Institute. In 1966, he became Institute Professor at M.I.T., and later in the same year resigned from the position of Provost in order to return to more intensive research, particularly in the fields of quantum electronics and astronomy. He was appointed University Professor at the University of California in 1967. In this position Dr. Townes is participating in teaching, research, and other activities on several campuses of the University, although he is located at the Berkeley campus.
During 1955 and 1956, Townes was a Guggenheim Fellow and a Fulbright Lecturer, first at the University of Paris and then at the University of Tokyo. He was National Lecturer for Sigma Xi and also taught during summer sessions at the University of Michigan and at the Enrico Fermi International School of Physics in Italy, serving as Director for a session in 1963 on coherent light. In the fall of 1963, he was Scott Lecture at the University of Toronto. More recently (2002-2003) he has been the Karl Schwarzschild Lecturer in Germany and the Birla Lecturer and Schroedinger Lecturer in India.
In addition to the Nobel Prize, Townes has received the Templeton Prize, for contributions to the understanding of religion, and a number of other prizes as well as 27 honorary degrees from various universities.
Dr. Townes has served on a number of scientific committees advising governmental agencies and has been active in professional societies. This includes being a member, and vice chairman, of the Science Advisory Committee to the President of the U.S., Chairman of the Advisory Committee for the first human landing on the moon, and chairman of the Defense Department’s Committee on the MX missile. He also served on the boards of General Motors and of the Perkins Elmer Corporations.
Dr. Townes and his wife (the former Frances H. Brown; they married in 1941) live at 1988 San Antonio Avenue, Berkeley, California. They have four daughters, Linda Rosenwein, Ellen Anderson, Carla Kessler, and Holly Townes.
