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Atomic, Molecular, and Optical Science: An Investment in the Future C Citation Analysis To explore the state of AMO science in the United States, a citation analysis was conducted using data provided by the Institute for Scientific Information (Philadelphia). Papers in AMO science were identified through the journals in which they appeared, and the data set comprised all the papers published in the journals listed in Table C.1. Recent trends were studied by analyzing the country of origin of the most highly cited (and thus presumably most significant) papers and by looking for changes in the distribution of the countries of origin of papers citing earlier work in AMO science. The country of origin of a cited or citing paper was determined from the author affiliations. In the small fraction of cases where a paper had contributions from authors affiliated with institutions in two (or more) countries, each of these countries was credited with a publication and/or citation. Self-citations could not be excluded. The countries of origin of the most highly cited papers in AMO science published in 1989 are shown in Figure C.1. These data include papers published in the journals listed in Table C.1, together with Applied Physics Letters, Nature, and Physical Review Letters. Only a fraction of the papers published in these latter journals are in AMO science, and the title of each individual paper was checked to determine if it was in the field. Each paper forming the sample analyzed in Figure C.1 (a total of 381 papers) has been cited at least 15 times since publication. However, the distribution evident in Figure C.1 was little changed if the cutoff was raised to papers with at least 20 citations (a total of 167 papers) or 25 citations (a total of 85 papers). Approximately 70% of the highly cited papers included in Figure C.1 have contributions from U.S. authors. Because it is reasonable to assume that the number of citations a paper receives
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Atomic, Molecular, and Optical Science: An Investment in the Future TABLE C.1 Journals Included in the AMO Citation Analysis Advances in Atomic, Molecular, and Optical Physics Advances in Chemical Physics Applied Optics Chemical Physics Chemical Physics Letters IEEE Journal of Quantum Electronics IEEE Photonics Technology Letters Infrared Physics International Journal of Mass Spectrometry and Ion Processes Journal of Chemical Physics Journal of Electronic Spectroscopy and Related Topics Journal of Lightwave Technology Journal of Luminescence Journal of Modern Optics Journal of Molecular Spectroscopy Journal of Optics Journal of Physical Chemistry Journal of Physics B Journal of Quantitative Spectroscopy and Radiative Transfer Journal of the Optical Society of America A Journal of the Optical Society of America B Molecular Physics Optica Acta Optical and Quantum Electronics Optics Communications Optics Letters Optik Optika I Spektroskopiya Physical Review A Progress in Optics Zeitschrift für Physik D NOTE: Applied Physics Letters, Nature, and Physical Review Letters were included when analyzing the countries of origin of the most highly cited papers in AMO science published in 1989. correlates with its importance to the field, this statistic speaks to the strength of AMO science in the United States, especially in universities. More than 80% of the papers included in the sample in Figure C.1 had contributions from university-based authors, whereas only about 30% had contributions from authors affiliated with either government or industrial laboratories. Of the papers included in Figure C.1, 13% represent international collaborations with authors from institutions in two or more countries. To ascertain how the U.S. contribution to the total worldwide effort in AMO science has changed in recent years, the countries of origin of papers citing AMO papers published in 1981 and 1989 in the journals listed in Table C.1 were examined. Figure C.2 shows the origins of papers that cited the 1981 papers
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Atomic, Molecular, and Optical Science: An Investment in the Future during the period from 1981 to 1983, and the 1989 papers during the period from 1989 to 1991. In this interval the total number of citations increased by about 36%, reflecting, in part, the growth of activity in the field. The data in Figure C.2 are therefore normalized to the total number of citations in each period to allow better visualization of trends. The data suggest that the U.S. contribution to the total worldwide effort in AMO science is substantial and has changed little in the past decade. Europe and Japan, however, also have strong programs in AMO science. To evaluate the ability of AMO science in the United States to respond to new opportunities and new ideas, the titles of the highly cited papers included in Figure C.1 were examined to identify ''hot topics." These were laser cooling, diode laser development, quantum chemistry/collision dynamics, femtosecond laser development, application of femtosecond lasers, and C60. Six representative papers in each area were then selected and the countries of origin of papers citing this work in the period from 1989 to 1991 examined. These are shown in Figure C.3, expressed as a percentage of the total number of citations in each area. Typically, about 56% of citations are associated with U.S.-based authors. This number is significantly higher than the approximately 40% typical of AMO science as a whole (see Figure C.2), indicating that the United States is especially strong in emergent new areas and has the resources and inventiveness to respond to new opportunities. FIGURE C.1 Countries of origin of the most highly cited papers in AMO science published in 1989. The bars show the percentage of these papers with contributions from authors affiliated with institutions in the countries indicated.
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Atomic, Molecular, and Optical Science: An Investment in the Future FIGURE C.2 Countries of origin of papers that cite papers in AMO science published in the journals listed in Table C.1 in (a) 1981 and (b) 1989. The citing intervals are 1981 to 1983 and 1989 to 1991, respectively. The horizontal bars represent the numbers of citations from each of the countries indicated expressed as a percentage of the total number of citations in each period. FIGURE C.3 Countries of origin of papers that cite papers in "hot topic" areas published in 1989, in the interval from 1989 to 1991. The horizontal bars represent the numbers of citations from each of the countries indicated expressed as a percentage of the total number of citations in each area.
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