International Coordination of A+M Data Efforts

R.K. Janev (Panel Chair)1, K.H. Becker2, R.E.H. Clark3,
G. Lister4, K. Niemax5

1International Atomic Energy Agency, Vienna, Austria
2Physics Department, Stevens Institute of Technology, Hoboken, USA
3Los Alamos National Laboratory, Los Alamos, USA
4OSRAM Sylvania Inc., Beverly, USA
5Institute of Spectroscopy and Applied Spectroscopy, Dortmund, Germany

Reproduced with permission from Atomic and Molecular Data and Their Applications
edited by P.J. Mohr and W.L. Wiese
© 1998 American Institute of Physics, New York, Conference Proceeding #434


A summary of the discussions at the ICAMDATA panel on international coordination of atomic and molecular (A+M) data efforts is presented. The status of databases and the needs for coordination of data generation, compilation and assessment efforts in the areas of spectrochemistry, low-temperature plasma applications, plasma processing of materials, lighting industry and fusion energy research are specifically addressed.


The progress in many scientific and technological areas in which atomic and molecular processes play an important role depends on the availability of accurate quantitative information on the collisional properties of these processes and spectroscopic characteristics of interacting species. The understanding of various astrophysical, atmospheric and biophysical phenomena, or the development and optimization of various technological processes and industrial devices relies on the knowledge of underlying physical and chemical mechanisms and on a detailed modeling of the corresponding atomic and molecular kinetics. The amount of required spectroscopic and collisional information for complete understanding and successful description of properties and behaviour of the gaseous and plasma media in natural or industrial systems may be extremely large. The generation of this information, either through compilation and critical assessment of the available literature data or through new experimental measurements and theoretical calculations, frequently appears to be an effort which is well beyond the capacity of a scientific or industrial laboratory, group of such laboratories, or even a nation. Astrophysics, fusion energy research, aeronomy and various low-temperature industrial plasma applications (such as plasma processing of materials, lighting devices, analytic spectrochemistry, etc) provide examples of research and technological development areas in which the establishment of required atomic and molecular databases needs coordination of the corresponding efforts on a transnational level. The international coordination of database establishment efforts in certain scientific or applied research field accelerates the process of database establishment, ensures the required scientific expertise for critical data assessment (and, thereby, the high quality of the data), and considerably reduces the required resources. Such collaborative efforts are advantageous also from technical point of view (e.g., unification of data presentation formats and data dissemination). Examples of very successful international database establishment efforts can be found in astrophysics (the OPACITY and the IRON projects), in magnetic fusion research (the AMDIS/ALADDIN and the ADAS databases) and in the atmospheric research (earth atmosphere photochemistry).

The ICAMDATA panel discussions on the international coordination of A+M data efforts focussed on the analysis of A+M data status and needs for coordination in the fields of spectrochemistry, low-temperature plasma applications, plasma processing of materials, lighting devices and controlled thermonuclear fusion. The highlights and conclusions of these discussions are summarized below.


Element analysis in spectrochemistry includes a wide range of measurement techniques, such as optical emission spectrosmetry, atomic absorption spectrometry, X-ray fluorescence, all of which involve a significant amount of spectroscopic data information. In recent years, the optical spectrometer in the techniques based on an inductively coupled plasma is more and more frequently replaced by a mass spectrometer in order to lower the element detection limits. Time-of-flight techniques have recently been also employed in this field because they allow for a simultaneous elements analysis. Further, the laser induced breakdown spectrometry, where a sample material is ablated by a pulsed laser and the transient spectra of the laser produced plasma are measured with intensified diode arrays or CCD - cameras attached to the spectrometers, is currently considered as a very promising analytical technique.

The spectroscopic data information associated with the application of the above (and other, less standard) spectrochemical techniques is to a large extent already available (mainly due to the activity of NIST/NBS data centres) and includes: wavelengths and (source dependent) intensities of spectral lines, energy levels, transition probabilities and lifetimes of atomic states, hyperfine structure, isotope shifts and spectral line broadening and shifts parameters. However, the spectroscopic data information for spectrochemical applications is far from being complete. Wavelength and spectral line intensity data are needed for metals and non-metals in the spectral range 150-800 nm (particularly for the weak lines which interfere with the strong ones). Atomic state energy and transition probability data are still needed for the species present in the analytical plasmas (for determining the plasma parameters) and for the laser spectrometry.

International collaboration in completing the spectroscopic data information required for advancing the spectrochemical analysis methods, as well as for other applications, would certainly be very useful for meeting the needs in a timely fashion. Such collaborations already exist on a bilateral level (e.g., between NIST and JAERI), but a wider coordination of the data efforts conducted in various national centres could be much more effective.


The use of non-equilibrium, low-temperature plasmas for materials processing is the key to the advancement of many rapidly developing technologies. The selective and highly anisotropic etching of materials and the controlled deposition of thin films in the fabrication of microelectronic structures are among the most important methods of plasma-assisted materials processing, plasma polymerization and plasma-assisted surface modification. Plasma-based processes are used in about 40 percent of the steps in the manufacture of semiconductor chips and the more sophisticated the chip, the larger the number of steps relying on plasma technology.

A low-temperature plasma is a system far from thermodynamic equilibrium. The electron temperature is much higher than the gas temperature and can drive "high-temperature" chemistry (without any adverse effects on the processed materials). The high-energy tail of the electron energy distribution function induces collisional break-up of the parent feedstock molecules which further leads to formation of chemically active neutral and ionic radicals and to a complex reaction kinetics. For modeling the behaviour and properties of such chemically active plasmas, a detailed quantitative information is required for the most important collisional and radiative processes taking place both in the gas phase and on the surfaces. The available data information depends on the specific technological plasma, and in the case of plasma deposition applications (where Si-organic and metal-organic compounds are used) the existing databases are particularly scarce. The collisional and spectroscopic databases for most technological plasma applications are inadequate for a full understanding of the corresponding plasma chemistry dynamics and full exploitation of the optimization potential of these reactive plasmas. A coordinated international effort to improve the current status of the A+M databases relevant to low-temperature plasmas used in plasma processing applications would be extremely useful for advancement of the corresponding technological development. The coordination effort should include data generation (experimental and theoretical), data collection and assessment, data distribution, as well as stronger interaction with the relevant industrial partners and national funding agencies. Establishment of an international data collection, evaluation and dissemination centre, entrusted also with a coordinating role, would be an attractive organizational form for such an effort.


Lighting devices are one of the traditional and still a vigorously developing field of low-temperature plasma applications. The gas discharges used in lighting devices (fluorescent lamps, HID, barrier discharge lamps, flat panel displays, etc) cover a wide range of plasma parameters, with electron temperatures in the range 0.1 - 2 eV, electron densities around 10;i:;sup:11;/sup:;/i:-10;i:;sup:13;/sup:;/i: cm;i:;sup:-3;/sup:;/i: and gas pressures from about 3 torr (in the fluorescent lamps) up to a few atmospheres (in HID lamps). The understanding of the chemistry, dynamics and radiative properties of these plasmas, required to optimize the device parameters (the most important of which are the lamp efficiency and lifetime), relies on the knowledge of collisional and spectroscopic characteristics of all relevant plasma constituents. This understanding and the way to device optimization is achieved by detailed plasma behaviour modeling and, in particular, calculation of level populations of active gas atoms. Besides the knowledge of collisional and radiative characteristics of plasma constituents, the plasma modeling requires also knowledge of the electron energy distribution function, which in some cases may not be Maxwellian (e.g., in barrier discharge lamps). Existence of a high-energy tail in the electron energy distribution function requires inclusion in the atomic database collisional and radiative processes involving highly excited states, which results in a drastic increase of the size of the database and the kinetic model calculations.

The recent developments in low pressure discharge technology for the lighting industry (electrodeless devices, small diameter cold cathode discharges) have led to new extensions of operating parameters of lighting devices with involvement of new important collisional and radiative processes and new working gas species (e.g., in the mercury free lamps). These developments have further expanded the diversity and quantity of the required collisional and spectroscopic information.

Despite the long and distinguished history of lighting research community to establish the required atomic databases, the present status is still unsatisfactory, particularly in view of new technology developments. A broad scale and well coordinated joint effort of the A+M and lighting research communities on establishing the required databases would be highly desirable for the further development of light sources. The establishment of such joint efforts, however, meets certain difficulties in the area of the intellectual property rights.


The atomic and molecular collisional and radiative processes play an important role in magnetic fusion devices as they influence the energy balance of the confined plasma, the plasma transport and radiation properties and are used as the basis for many plasma diagnostic methods. The design and operation of some vital fusion device systems, such as the neutral beam heating, the impurity control and the thermal power and particle exhaust systems, require large amounts of atomic and molecular collisional and radiative data. The overall A+M data information needed in fusion energy research is enormous and the need for coordination of the A+M data acquisition efforts on an international level has become evident already at the beginning of seventies. In response to this need, the International Atomic Energy Agency (IAEA) has established (1975) an activity on compilation, evaluation and dissemination of A+M bibliographic and numerical data for fusion and was charged (by the International Fusion Research Council) to coordinate the national A+M data efforts for fusion. Soon after, an international A+M Data Centre Network was established (with participating data centres from USA, UK, Russia, Japan and France) which presently includes about 15 data centres. Apart from coordinating the activities of this Data Centre Network on the establishment of evaluated and/or recommended international A+M databases for fusion, the IAEA organizes and supports additional international coordinated research programmes for enhancing the A+M data generation for fusion. More than 40 laboratories and theoretical groups are currently involved in the data generation (and critical data assessment) effort. The results of the IAEA coordinated A+M data activities for fusion are contained in the IAEA Atomic and Molecular Data Information System (AMDIS), the databases of which are online accessible (via Internet and WWW).

The establishment of the international A+M database for fusion is an example (among many others) which illustrates the usefulness of the coordination of A+M data efforts for creating a comprehensive database for certain field of scientific or technological research. This example also reveals the necessary conditions for a successful coordination of the A+M data efforts on establishing a database for a research field (or a specific research subject): (i) clear identification of the needs for such data (the users community), (ii) identification of the research groups, laboratories or data centres which jointly have the potential to provide (compile, evaluate and/or generate) the required data, (iii) establishment of an effective mechanism for work coordination, (iv) availability of adequate funds (normally provided by the data users or national funding agencies) and (v) resolved situation regarding the intellectual property rights.


Although limited in the scope (due to the time constrains), the panel discussions have shown that the A+M collisional and radiative processes play an essential role in many modern science and technology areas and that the quantitative information about these processes is instrumental for the further progress in these areas. The research and development fields analysed at the panel (spectrochemistry, industrial and technology plasma applications, fusion energy research) have demonstrated that there are urgent needs for establishing comprehensive and reliable A+M databases for the advancement of these fields. Coordination of world-wide efforts on establishing such databases is found to be advantageous for rapid and efficient achievement of the development goals (as has been demonstrated in the case of fusion energy research). The coordination of database establishment efforts in the areas of industrial and technology plasma applications requires fulfillment of certain conditions (see the last part of the previous section), the most critical of which are those related to the funding and intellectual properties rights. The interaction and constructive dialogue of all factors involved in a database establishment process may help in removing these difficulties.
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