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Atomic, Molecular, and Optical Physics in the United States Today This chapter summarizes the demographics of atomic, molecular, and optical (AMO) physics and outlines some of its contributions to the community of science and to the nation. The concluding section discusses the changing role of the United States in AMO research. DEMOGRAPHICS OF ATOMIC, MOLECULAR, AND OPTICAL PHYSICS The most comprehensive recent study of AMO physics in the United States is the Survey by the Committee on Atomic and Molecular Science (CAMS).* We briefly summarize here the major points. Size of the Field Based on 2264 returned questionnaires (from an initial mailing of 6000), the Survey estimates that the community of professional scien- tists actively working in atomic and molecular science in the United States is approximately 3000. *Subcommittee on Atomic and Molecular Survey, NRC Committee on Atomic and Molecular Science, Survey of Atomic and Molecular Science in the United States, 1980-1981, National Academy Press, Washington, D.C., 1982. 29

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30 ATOMIC, MOLECULAR, AND OPTICAL PHYSICS Employment Academic institutions Industrial or corporate research Federally funded research and development centers Government laboratories (civilian or military) Not-for-profit research organizations Distribution of Effort 52% 18% 15% 11% 4% Within broad categories, the research effort is distributed as follows: Structural properties of atoms and molecules Atomic and molecular collisional interactions Interactions with radiation Techniques and instrumentation Interfaces with other areas of science and technology The breakdown between experimental and theoretical work is Primarily experimental Experimental and theoretical Primarily theoretical 19% 25% 25% 12% 19% 54% 20% 36% THE EDUCATIONAL ROLE OF ATOMIC, MOLECULAR, AND OPTICAL PHYSICS AMO physics plays an active role in educating scientists in the United States at both the undergraduate and graduate levels. Because the field is one of a small number in physics that permit experimental research in a college setting, AMO physicists are frequently sought for teaching positions in colleges. AMO physics often plays a prominent role in undergraduate education in universities because its laboratories are generally located on campus and the research lends itself to participation by students. By providing research opportunities for undergraduate students in colleges and universities, AMO research plays an effective role in attracting capable students to science. The major educational role of AMO physics, however, is in the training of professional physicists who are qualified to pursue many

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AMO PHYSICS IN THE UNITED STATES TODA Y 31 different careers in science. AMO research is generally carried out in small groups; it is not unusual for a student to execute an entire experiment single-handedly under the direction of a supervisor constructing the apparatus, taking and analyzing the data, and working out the theory. The research requires experimental skills including mechanical design and construction, high-vacuum techniques, elec- tronics, lasers, electron and optical spectroscopy, charged and neutral particle beams, and computers. Often a student working in AMO physics becomes expert in several of these areas. Furthermore, in AMO physics it is possible for a single person to work actively both in theory and in experiment, providing an unusually versatile capability. These skills are invaluable for careers ranging from basic physics and chemistry to applied science and engineering. AMO physicists are in demand for positions in national laboratories and in industry. In national laboratories, for instance, a continued supply of AMO physicists is essential for the development of lasers for applications such as underwater communication, isotope separation, satellite tracking, and defense systems. AMO physicists are deeply involved in fusion research and in environmental monitoring programs. AMO physicists are needed by industry in areas of advanced technol- ogy such as fiber-optics communications, laser manufacturing, com- bustion analysis, optical data processing, photochemistry, and materi- als preparation. SCIENTIFIC INTERFACES AND APPLICATIONS AMO physics contributes broadly to neighboring fields of physics and to other areas of science. Some of the contributions take the form of devices and techniquesthe panoply of lasers, light-scattering spectroscopy, supersonic molecular-beam methods, clusters, surface- scattering spectroscopy, and spin-polarized quantum fluids, to name a few. Others are at the deepest scientific level, as for instance in astrophysics (see Chapter 7, section on Astrophysics) or at the interface between nuclear and atomic phenomena (see Chapter 7, section on Nuclear Physics). In addition, AMO physics provides atomic and molecular data, which are essential to fields such as plasma physics and atmospheric science. AMO physics contributes directly to national needs through a host of applications: plasma diagnostics based on AMO physics are essential to our fusion program; fiber-optics systems play a growing role in civilian and military communications; remote sensing is being increas- ingly employed for monitoring the environment and industrial pro-

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ATOMIC. Mf)LECIJI.AR Awn f,PT~f:Ar P~rYcrrc FIGURE 2.1 Remote Sensing Using Lasers. With lasers it is now possible to detect minute traces of chemicals from a distance. In environmental and energy programs the new techniques can be used to detect pollutants in the atmosphere sensitively and rapidly, to study aerosols and smog, to measure turbulence and wind velocity, and to monitor the stratospheric ozone layer. The techniques can also be employed to study combustion in a furnace or in engines while they operate. The illustration shows a blown-up three-dimensional map of the concentration of ethylene glycol that has leaked to the atmosphere from an oil refinery in Germany. The map is superimposed on an aerial photograph of the refinery. (The long arrows illustrate the points on the ground that correspond to the corners of the map.) The gas leak was mapped with a laser 0.5 kilometer away from the plant. The sensitivity of the measurement is 20 parts in 109. The peaks in the map reveal two sources of escaping gas. The gas is not coming from the two smokestacks that can be seen in the photo, however; the sources were pinpointed to be two leaks in separate buildings. (Photo courtesy of Max-Planck-Institute for Quantum Optics, Garching, Federal Republic of Germany.) cesses such as combustion (see Figure 2.11; and laser processing is expected to have a revolutionary impact on manufacturing. AMO physics is vital to innumerable military applications including naviga- tion, communication, and laser-based defense systems; it has contrib- uted to medical care through laser surgery and nuclear magnetic resonance body imaging. Chapters 7 and 8 describe the scientific interfaces and applications of

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AMO PHYSICS IN THE UNITED STATES TODAY 33 AMO research. The activities are broad, and the chapters are by no means comprehensive. Nevertheless, they provide evidence of the many contributions of AMO research to science and to society. THE ECONOMIC IMPACT OF ATOMIC, MOLECULAR, AND OPTICAL PHYSICS Over a long period- and sometimes quickly basic science repays the investment. The return from AMO physics is often large and sometimes rapid. Assessing the full economic impact of AMO physics would be a formidable task, but a few representative examples can help to indicate the magnitude of the return. Nuclear magnetic resonance, whose origins trace back to molecular-beam magnetic resonance, has been applied to a new type of body imaging for medical diagnosis (see Chapter 8, section on Medical Physics). Although the technique is still in its infancy, more than 20 companies are already developing magnetic resonance imaging machines, and hospitals have started to install the devices. The projected sales by 1990 are estimated to be $2 billion to $3 billion. The economic impact of magnetic resonance body imaging is far greater than this, however, for it comes not so much from the sales as from the benefits of improved medical diagnosis: high productivity, better health care, and a better quality of life. The major economic return from AMO physics in the past decade came from the laser and the developments of modern optics. The conception, development, and reduction to practice of the laser and other modern optical techniques provides a striking illustration of the confluence of academic and industrial research and development in AMO physics. In 1982, the total commercial sales for lasers, laser equipment, and services were $1.5 billion. The laser is having a revolutionary impact on some industries; the fiber-optic industry illustrates how rapidly a new technology can grow. It was not until the mid-1970s, when low-loss fibers were first developed, that commercial applications became a realistic possibility. In 1981 the sales were $24 million; by 1983 they were $620 million. Annual sales in fiber optics in 1990 are projected to be $1.4 billion. The total sales of laser printing equipment through 1988 are projected to be between $5 billion and $10 billion. The role of lasers and modern optics in industrial applications such as robotics, laser manufacturing, and photochemical processing can be expected to strengthen the nation's economy for years to come. (See Figure 2.2. The use of lasers in manufacturing is described in Chapter 8 in the section on Materials Processing.) These industries are vital to

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34 ATOMIC, MOLECULAR, AND OPTICAL PHYSICS FIGURE 2.2 Laser-Assisted Manufacturing. Industry is finding more and more uses for lasers, and with the robotics revolution laser-assisted manufacturing promises to become a major industrial force. Laser light is particularly well suited to robotics because the energy can be directed and controlled by computer with unmatched speed and accuracy. Manufacturing processes in which lasers are used include cutting, drilling, welding, surface hardening, and specialized applications such as machining gemstones, ceramics, and semiconductors. Material from the most delicate foil to steel plate O.S-inch thick can be machined. The upper photograph shows a heavy-duty laser machining installation that cuts, drills, and welds parts in a wide range of geometries. At lower left is an internal gear that was processed by a laser drill. At lower right, the container for a cardiac pacemaker made of titanium is shown being welded by a pulsed laser welder. Further discussion is in Chapter 8 in the section on Manufacturing with Lasers. (Photos courtesy of Lasers and Applications.)

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AMO PHYSICS IN THE UNITED STATES TODAY 35 the national interest if the United States is to compete successfully with other nations in these times of rapid technological development. One study of the patterns of future employment in the United States* indicates that by 1990 there will be 200,000 new jobs in the United States in industries related to fiber-optics communications. The use of lasers in manufacturing will generate even more employment: it is predicted that by 1990 the number of these new jobs will be 600,000. In assessing the economic role of AMO physics, the origin of the laser is worth recalling. The progenitor of the laser was the ammonia beam maser, which was conceived and developed in an academic AMO physics laboratory. Since these early beginnings AMO physics in industrial, academic, and government institutions has made innumer- able contributions to the development of lasers and laser-related optical industries. The growth of these industries stands as testimony of the economic return to society that can occur when capable scientists in AMO physics are given the freedom and resources to pursue their goals. THE HEALTH OF THE FIELD IN THE UNITED STATES Through the early 1970s, scientific leadership in AMO physics came largely from the United States. Advances such as the invention of magnetic resonance, the discovery of the Lamb shift, the observation of quantum diffraction in high-resolution atomic scattering, and the invention of the laser left no room for doubt about the strength of AMO physics in the United States. The situation is changing. AMO physics was enthusiastically supported in Europe during the past decade, while in the United States it experienced a period of austerity. As a result, the relative level of activity in Europe has advanced dramatically. Europe is now fully competitive with the United States. In accelerator-based atomic physics, the Europeans and Japanese are likely soon to establish a clear technological advantage. One of the most important new technologies, highly charged ion sources, has been vigorously developed in Europe: the lack of support for developing these sources in the United States makes it difficult for laboratories in this country to pursue research in this scientifically exciting area. If judged by the relative numbers of contributed papers at the Interna- tional Conference on the Physics of Electronic and Atomic Collisions, *Newsweek, Vol. 100, p. 78, Oct. 18, 1982. Based on data from the Bureau of Labor Statistics, Forecasting International, Ltd., and Occupational Forecasting, Inc.

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36 ATOMIC, MOLECULAR, AND OPTICAL PHYSICS activity in atomic and molecular scattering in Europe has grown conspicuously. In 1971, the breakdown was 47 percent United States versus 36 percent Europe and United Kingdom; in 1983 it was 26 percent versus 54 percent, respectively. Both meetings were held in Europe. In the early 1970s, there were but a handful of groups at German universities working in optical physics and lasers. Most of the ad- vances in this field came from laboratories in the United States. The rapidly rising number of German publications reveals that this is no longer true. West Germany has assumed a forefront position. In 1974, the Deutsche Forschungsgemeinschaft initiated a program to provide funds for acquisition of modern laser equipment by researchers in German universities. As a result, there were periods when major United States laser manufacturers were shipping more than half of their production to Germany. Most German AMO physics groups now have several state-of-the-art laser systems. In the United States, however, most laboratories could not afford to purchase essential equipment. U.S. laboratories now suffer from a serious lack of lasers. Fifty percent of AMO research involves lasers; the shortage of these devices affects practically every area of AMO research in the United States. There are many excellent AMO research groups in the United States, and there are numerous opportunities for scientific advance. A central concern, however, is that if one extrapolates the effect of the funding pattern over the past decade into the decade to come, it becomes evident that the quality of AMO research in the United States will be seriously compromised. It is not essential that the United States be preeminent in every area of AMO research, but we must remain competitive and we must maintain excellence in areas where major advances seem likely. We have attempted to define those areas in the Program of Research Initiatives. To assure the continued vitality of AMO physics in the United States it is essential to move forward vigorously on these research initiatives.