The Mössbauer effect data center: A report

The Mössbauer Effect Data Center is unique in its operation and the kind of information services that it provides. It is probably the only user-supported information center in the basic sciences. This has been primarily possible due to the broad support and encouragement the center receives from the international Mössbauer community. This report also discusses the demographics of the Mössbauer community: identifying such items as the most active areas of research in Mössbauer Spectroscopy, where is this research being done and who is doing it. Also, examined is where Mössbauer research investigations are being published. BITNET and other forms of electronic mail are being widely used in the scientific community. This is also the case in the Mössbauer community. Directories and list-servers are being established.     

The Mössbauer research community: A report

The Mössbauer research community has gone through various stages of development in its 30⁺ year history. Signs of maturity of the Mössbauer effect is shown in the number of experimental applications, the number of Mössbauer transitions that are available and the large number of scientists that have been and are involved with Mössbauer research. In recent years, there has been a significant increase in the number of publications using Mössbauer Spectroscopy to investigate both amorphous and high temperature superconductor materials. This overall growth in the Mössbauer scientific literature has been 6–7% per year since 1984, while during the preceding period there was no increase in the number of publications per year. The Mössbauer Effect Data Center continues to make use of the various developing technologies in the area of computers and communications. The Center recently completed a ten-year project of bringing together all its databases into one computer system. Also, the Center has recently completed the development of a new approach to the dissemination of information by making available subsets of the Mössbauer database on PC computer disks. The future of the Data Center will focus significant attention on networking strategies with the Mössbauer research community.     

The USA and International Mössbauer Community

In the four decades since Rudolph L. Mössbauer's two papers launched the research community, almost 50,000 Mössbauer publications have appeared in the scientific literature. Most of the early pioneers have departed in recent years for various reasons. The Mössbauer society's international collaborations, the breadth of research topics in the field, and what has been and is being investigated are analyzed. The Mössbauer Effect Data Center's central role in the community over the years is discussed.     

The Mössbauer community in the USA

Scientists in the United States assumed major roles in developing the Mössbauer community during its early years. However, since the termination of the Mössbauer Effect Methodology meetings in 1976, there has been little in the way of regular Mössbauer meetings in the United States. Nevertheless, there is an active United States Mössbauer community, as noted by the number of annual publications – 156 in 2004. In recent decades, attendance of Mössbauer researchers from the United States at the International Conferences on the Applications of the Mössbauer Effect (ICAME) has been far below what would be expected from the number of contributions in the Mössbauer literature. Attempts have been made, unsuccessfully, to arrange for regular Mössbauer meetings. Models for possible future Mössbauer meetings of US scientists are discussed, including a regular biannual meeting, and another being a virtual Mössbauer conference. Also discussed are other models to maintaining an active Mössbauer community in the United States, making use of information technologies that are available to us along with other resources we can use.     

Mössbauer spectroscopy applied to biological systems

Biological materials provide excellent examples of a number of different types of system which are of intrinsic scientific interest and are also amenable to investigation by Mössbauer spectroscopy. This review will consider studies in several areas which typify this aspect of Mössbauer spectroscopy applied to biological materials and which illustrate the range of behaviour that can be observed.     

Artificial neural networks in Mössbauer material science

Mössbauer spectroscopy is a useful technique for characterizing the valencies, electronic and magnetic states, coordination symmetries and site occupancies of the cation. The Mössbauer parameters of isomer shift and quadrupole splitting are useful to distinguish paramagnetic ferrous and ferric iron in several substances, while the internal magnetic field provides information on the crystallinity. In recent years artificial neural networks have shown to be a powerful technique to solve problems of pattern recognition of a mineral from its Mössbauer spectrum, Mössbauer parameters data bank, crystalline structure and magnetic phases of soil from Mössbauer parameters. A computer software named Mössbauer Effect Assistant has been developed. It uses learning vector quantization neural network linked to a Mössbauer data bank that contains Mössbauer parameters of isomer shift, quadrupole spliting, internal magnetic field and the references of the substances. The program identifies the substance under study and/or its crystalline structure when fed with experimental Mössbauer parameters. It can also list the references from the literature by feeding the name of the substance or the author of the publication. Typical application of Mössbauer Effect Assistant in iron-bearing materials Mössbauer spectroscopy is present in user friendly Microsoft Windows environment.     

Mössbauer diffraction and interference studies of polycrystalline metals and alloys

After a review of previous work on Mössbauer diffraction and interference phenomena, the principles of the kinematical theory of Mössbauer diffraction are presented. The emphasis is on how the spectroscopic capabilities of the Mössbauer effect can be used to advantage in diffraction studies on materials and condensed matter. Experimental results from Mössbauer powder diffractometry experiments are presented. These results identify the difficulties of Mössbauer powder diffraction experiments, but also demonstrate that a unique chemical environment selectivity is possible for Mössbauer diffraction. Future experiments with Mössbauer powder diffraction require the development of efficient detectors, and some possibilities are suggested.     

MossWinn—methodological advances in the field of Mössbauer data analysis

The methodology of Mössbauer data analysis has been advanced via the development of a novel scientific database system concept and its realization in the field of Mössbauer spectroscopy, as well as by the application of parallel computing techniques for the enhancement of the efficiency of various processes encountered in the practice of Mössbauer data handling and analysis. The present article describes the new database system concept along with details of its realization in the form of the MossWinn Internet Database (MIDB), and illustrates the performance advantage that may be realized on multi-core processor systems by the application of parallel algorithms for the implementation of database system functions.     

Mössbauer effect: a dual method for myriad applications

This essay summarises the author’s admittedly partial thoughts on the applications of the Mössbauer effect. After a short overview of the history of Mössbauer effect and Mössbauer spectroscopy, we focus on recent difficulties of the applications of the method. These emerge from the complexity of Mössbauer spectroscopy, which is now extensively used by experts of other fields. Finally the plan of setting up a Web-based Encyclopaedia of Mössbauer Spectroscopy is put forward.     

Mössbauer scattering spectroscopy

The Mössbauer scattering spectra detected by γ-and X-radiation are investigated, and an analytical representation for the scattering integrals is given. It is shown that the use of Mössbauer scattering spectroscopy allows us to determine the interference amplitude, angular correlation function, Debye-Waller factor for Rayleigh scattering, Lamb-Mössbauer factors and linewidths for the source and scatterer, electronic attenuation coefficients of γ-and X-radiation for the scatterer, the total attenuation coefficient of γ-radiation for Rayleigh and Compton scattering, photoabsorption coefficient of γ-radiation in the scatterer and K-shell of⁵⁷Fe, resonance absorption coefficient of Mössbauer radiation, the thickness of the scatterer and the number density of Mössbauer elements in it. An experimental procedure for checking the difference in Lamb-Mössbauer factors for absorption and scattering of Mössbauer radiation is proposed.     

Advances in Mössbauer data analysis

The whole Mössbauer community generates a huge amount of data in several fields of human knowledge since the first publication of Rudolf Mössbauer. Interlaboratory measurements of the same substance may result in minor differences in the Mössbauer Parameters (MP) of isomer shift, quadrupole splitting and internal magnetic field. Therefore, a conventional data bank of published MP will be of limited help in identification of substances. Data bank search for exact information became incapable to differentiate the values of Mössbauer parameters within the experimental errors (e.g., IS = 0.22 mm/s from IS = 0.23 mm/s), but physically both values may be considered the same. An artificial neural network (ANN) is able to identify a substance and its crystalline structure from measured MP, and its slight variations do not represent an obstacle for the ANN identification. A barrier to the popularization of Mössbauer spectroscopy as an analytical technique is the absence of a full automated equipment, since the analysis of a Mössbauer spectrum normally is time‐consuming and requires a specialist. In this work, the fitting process of a Mössbauer spectrum was completely automated through the use of genetic algorithms and fuzzy logic. Both software and hardware systems were implemented turning out to be a fully automated Mössbauer data analysis system. The developed system will be presented.     

Application of 57Fe Mössbauer spectroscopy as a tool for mining exploration of bornite (Cu5FeS4) copper ore

Nuclear resonance methods, including Mössbauer spectroscopy,are considered as unique techniques suitable for remote on-line mineralogical analysis. The employment of these methods provides potentially significant commercial benefits for mining industry. As applied to copper sulfide ores, Mössbauer spectroscopy method is suitable for the analysis noted. Bornite (formally Cu₅FeS₄) is a significant part of copper ore and identification of its properties is important for economic exploitation of commercial copper ore deposits. A series of natural bornite samples was studied by ⁵⁷Fe Mössbauer spectroscopy. Two aspects were considered: reexamination of ⁵⁷Fe Mössbauer properties of natural bornite samples and their stability irrespective of origin and potential use of miniaturized Mössbauer spectrometers MIMOS II for in-situ bornite identification. The results obtained show a number of potential benefits of introducing the available portative Mössbauer equipment into the mining industry for express mineralogical analysis. In addition, results of some preliminary ^63,65Cu nuclear quadrupole resonance (NQR) studies of bornite are reported and their merits with Mössbauer techniques for bornite detection discussed.     

Mössbauer spectroscopy on the surface of Mars. Why?

A Mössbauer spectrometer is included in the preliminary payload of a rover to be placed on the surface of Mars in the Soviet mission to the planct in 1996/1,2/. In counection with the American planctary program it has also been suggested to construct a Mössbauer spectrometer to be landed on Mars /3, 4/. The objective is to study the iron compounds of the Martian soil and rocks by backscattering Mössbauer spectroscopy. The paper describes the significance of the element iron in the study of the evolution of the planetary system and what we might expect to learn from Mössbauer spectroscopy of the surface materials of Mars. The study of Mars is expected to expand substantially in the coming decades, probably culminating with a manned flight to the planet. The international Mössbauer community may contribute significantly to the preparation of these events.     

Precise determination of hyperfine interactions and second-order doppler shift in <Superscript>149</Superscript>Sm Mössbauer transition

We have succeeded in precisely determining the hyperfine interactions, particularly the isomer shifts, in the ¹⁴⁹Sm Mössbauer transition. The difference in the nuclear radii between the ground and excited states is critical for the determination of isomer shifts but is relatively small in ¹⁴⁹Sm. Therefore, the precise determination by ¹⁴⁹Sm Mössbauer spectroscopy is difficult. The recent development of synchrotron-radiation-based Mössbauer spectroscopy allows the isomer shifts to be determined more precisely than previously with the help of wellcollimated synchrotron radiation. In particular, the time-window effect assists the precise determination of hyperfine interactions in the ¹⁴⁹Sm Mössbauer transition because this effect enables us to measure spectra with higher energy resolution than natural linewidth determined by the lifetime of the excited states. Meanwhile, highenergy-resolution measurements to determine center shifts by SR-based Mössbauer spectroscopy enable us to observe the second-order Doppler shift, which has not been discussed, particularly for heavy Mössbauer nuclei. We have discussed the precise determination of isomer shifts and the observation of the second-order Doppler shift using ¹⁴⁹Sm synchrotron-radiation-based Mössbauer spectroscopy.     

Perspectives in physical metallurgy

Physical metallurgy experienced a tremendous, impact with the advent of the Mössbauer effect. Some of these developments will be reviewed, in particular the role of⁵⁷Fe as the star performer in Mössbauer spectroscopy. Also, one must realize that in most casen metals are involved, either in the source, the absorber, or both. Mössbauer spectroscopy in its different variations (conversion electron-, conversion x-ray-, γ-transmission Mössbauer spectroacopy) is well suited for the analysis of iron based alloys. An instrument has been developed which allows simultancous triple radiation Mössbauer spectroscopy (STRMS). The backscalttering geometry of CEMS and CXMS in conjunction with the transmission mode permits non-destructive testing of surfaces and depth analysis.     

The effect of decaying atomic states on integral and time differential Mössbauer spectra

Mössbauer spectra for time dependent monopole interaction have been calculated for the case that the nuclear transition feeding the Mössbauer state excites an electronic state of the atom. This is assumed to decay in a time comparable with the lifetime of the Mössbauer state. Spectra have been calculated for both time differential and integral experiments.     

Mössbauer investigations on glass-forming organic liquids

Glycerol forms a molecular glass near 180K. Fe²⁺ dissolved in glycerol allows the study of the dynamics of the system by Mössbauer spectroscopy. Recently it has been shown that the Mössbauer spectra can be understood in a way consistent with the results of dielectric and ultrasonic viscoelastic relaxation measurements. A jump diffusion model of Sinqwi and Sjolander with a jump rate distribution according to Davidson and Cole allowed us to fit the Mössbauer spectra of Fe in glycerol. First attempts to compare mode coupling theory with Mössbauer spectra are reported.     

A report from the Mössbauer effect data center

While interest in Mössbauer spectroscopy has continued at a high level during the last ten years, there is no apparent growth or decline, based on several indicators. It should be noted that there are several trends, both in the areas of who is doing Mössbauer spectroscopy and what topics are being investigated. The Mössbauer Effect Data Center continues to develop its capability of providing the information needs for the community of Mössbauer spectroscopists. New developments at the Center are a continuation of a long history of maintaining a center which is using the most recent available hardware and software capabilities.     

Mössbauer effect of 129I in L-3, 5-diiodotyrosine and l-thyroxine

We have used the Mössbauer effect of ¹²⁹I to study iodine bonding in L-3, 5-diiodotyrosine and L-thyroxine. We find identical Mössbauer spectra for the compounds, and the iodine sites in each compound are indistinguishable with the Mössbauer effect. The data indicate a small s hybridization in the iodine bonding orbitals.