Regional Groups of Mössbauer Researchers - United States

Reprinted from the September 2001 edition of the Mössbauer Spectroscopy Newsletter, published as part of Volume 24, Issue 7 of the Mössbauer Effect Reference and Data Journal

Mössbauer Spectroscopy in the United States

In response to a general call for information on the current Mössbauer research that is taking place in the United States, the following reports were received by the Mössbauer Effect Data Center.

Argonne National Laboratory
Argonne, Illinois

Names of Researchers

E. Ercan Alp

Wolfgang Sturhahn

Thomas S. Toellner

Jiyong Zhao

Michael Y. Hu

Caroline L’abbe

Front L-R: Caroline L’abbe, Wolfgang Sturhahn; Standing L-R: Michael Hu, Gopal Shenoy, Ercan Alp, Phillip Mannheim, Thomas Toellner, Harry Lipkin
Photo courtesy of S. Niehoff, Argonne

History and Areas of Research

The Mössbauer spectroscopy-related activities at Argonne National Laboratory are focused on the use of synchrotron radiation for elastic and inelastic nuclear resonant scattering studies of materials. The group, formally organized as the High Resolution X-Ray Scattering Group at the Advanced Photon Source (APS), is involved in developing x-ray optics for Tm, Kr, Fe, Eu, Sn, and Dy Mössbauer isotopes. A dedicated beamline (SRI-CAT, 3 ID) with two tandem undulators provide 1014-to-1013 photons/sec/eV in the energy range of 6-30 keV, respectively. The high resolution monochromators with meV bandpass and large energy tunability are available for these isotopes.

The group works closely together with Harald Sinn and Ahmet Alatas, who are focused on momentum-resolved inelastic x-ray scattering technique. Dr. Gopal K. Shenoy is the senior scientific director of the APS, and he actively follows the research in nuclear resonant scattering. The group is regularly visited by Harry Lipkin of the Weizmann Institute, Phillip Mannheim of the University of Connecticut, and Dennis Brown and Clyde Kimball of Northern Illinois University. The group also enjoys occasional interaction with the first-generation Mössbauer spectroscopists at Argonne National Laboratory, such as Gilbert Perlow and John Schiffer.

The scientific focus of the experiments is the application of inelastic nuclear resonant scattering to a variety of scientific fields, including geophysics, biophysics, and materials science. In addition, there are x-ray interferometry and x-ray metrology-related activities. The group's recent publications and information about the beamline capabilities, and how to ask for beamtime, can be found by sending an e-mail to E. Alp (eea@aps.anl.gov), W. Sturhahn (sturhahn@aps.anl.gov), H. Sinn (sinn@aps.anl.gov), or T. Toellner (toellner@aps.anl.gov).

University of Missouri–Rolla
Rolla, Missouri

Names and Titles of Researchers

Dr. Gary J. Long, Professor of Chemistry
Dr. O. A. Pringle, Professor of Physics
Dr. Fernande Grandjean, Adjunct Professor of Chemistry (UMR) and Professor of Physics (University of Liege)

History and Areas of Research

The Mössbauer effect laboratory in the Department of Chemistry at the University of Missouri–Rolla was established in 1968 under the direction of Dr. Long. He is assisted in direction of the laboratory by Dr. Grandjean and Dr. Pringle. Over the years the laboratory has been involved in several international cooperative scientific research projects. The most current project involves work on hard magnetic materials with Professor Olivier Isnard of the Université J. Fourier, Grenoble, France.

Two students have recently received their doctoral degrees based upon work in this laboratory. Dr. Sanjay Mishra, who received a Ph.D. in physics, is now an Assistant Professor of Physics at the University of Memphis, and Dr. Dimitri Hautot, who received his Ph.D. in chemistry, is a research postdoctoral fellow at the Davy Faraday Research Laboratory of the Royal Institution of Great Britain in London. Two students are currently working towards their doctoral degrees in the Mössbauer effect laboratory. The laboratory has five spectrometers and is capable of working between 1.9 and 1000 K with iron-57, tin-119, and antimony-121 and is capable of measuring room temperature conversion electron Mössbauer spectra. Over 240 research papers, 10 books, and 25 chapters dealing with Mössbauer spectroscopy and related topics have been published since 1968.

The research work of the laboratory can be divided into several topics. One of these deals with inorganic chemistry and the the study of the spin-state crossovers in iron(II) compounds, the new high figure of merit thermoelectric materials, such as skutterudites and tin clathrates, and sonochemically prepared materials. Another field of study involves intermetallic compounds of importance as hard permanent magnetic materials and has involved the study of a variety of R2Fe17 compounds and their hydrides and related intermetallic compounds with record low iron-57 isomer shifts. Another topic deals with various iron oxides, iron containing oxidic minerals, and nanostructured materials.

Old Dominion University
Norfolk, Virginia

The experimental Mössbauer Research Group is a part of the Condensed Matter and Materials Physics (CMMP) Research Group in the Physics Department at Old Dominion University (ODU). The Group’s director is Dr. Desmond C. Cook. Additional information regarding the Group can be found at its Web site: <www.physics.odu.edu/~cmmp>.

Names and Titles of Researchers

Dr. Desmond C. Cook, Professor of Physics
Dr. Gilbert R. Hoy, Professor of Physics
Rama Balasubramanian, Graduate Research Assistant
Dr. Masato Yamashita, Assistant Professor of Mechanical Engineering, Himeji Institute of Technology, Japan, Visiting Scientist

History and Areas of Research

The Mössbauer Group was formed in 1978 by Dr. Hoy, who moved from Boston University to become Chair of Physics at ODU. In 1981, Dr. Cook joined the group as Assistant Professor, coming to ODU from Monash University. During the 1980s, research projects included investigations on hemoglobin, iron doped semiconductors, and ferrites. The late 1980s saw Dr. Hoy involved in gamma ray optics and Dr. Cook moving towards research in nanophase materials, metal coatings, and corrosion in steels. Both researchers are still involved in these research fields. Dr. Cook is involved with the Corrosion Research Program, an international collaboration involving scientists in the United States, Mexico, Japan, and Colombia. Its primary mission is to investigate the environmental influences on the corrosion in structural steels in tropical marine and other regions of high chloride deposition. Of particular interest is the corrosion of new High Performance Steels used for bridges in the US and Japan.

The Group's recent projects include:

  • High Nitrogen Steels and Mechanical Procession of Iron Alloys in Nitrogen

  • Iron-Zinc Alloys and Galvannealed Steel used in Automotive Applications

  • Corrosion of Steel in Tropical Regions of the Gulf of Mexico

  • Corrosion of Structural Steel used in Bridges in the US

Mössbauer facilities at ODU include (1) three room-temperature spectrometers (one high precision on optical table), (2) three cryogenic systems to 4K, one including 8T longitudinal magnet for cold source/absorber, (3) scattering Mössbauer including conversion electron (CEMS) and toroidal gamma and x-ray scattering, and (4) Mössbauer oven to 1200K.

Emory University
Atlanta, Georgia

Names and Titles of Researchers

Boi Hanh Vincent Huynh, Ph.D., Professor of Physics
Carsten Krebs, Ph.D., Senior Postdoctoral Research Associate
Guy N. L. Jameson, Ph.D., Postdoctoral Research Associate
Gupta P. Govind, Visiting Research Associate

Areas of Research

Iron-containing proteins catalyze a variety of important biological functions including oxygen transport, oxygen activation, electron transport, regulatory and sensing functions. The group at the Rollins Research Center, Department of Physics, is interested in the applications of Mössbauer, EPR, and rapid-kinetic techniques to study the structural and functional properties of the iron centers in proteins. The group’s goals are to determine the roles that iron plays in the functions of these proteins and to identify protein structural factors that control the iron center reactivity in proteins. Current research focuses are on the oxygen activation mechanism of non-heme diiron enzymes, such as ribonucleotide reductase, methane monooxygenase and ferritin, and on the biosynthesis and novel functions of iron-sulfur proteins.

Los Alamos National Laboratory
Los Alamos, New Mexico

Names of Researchers

Dr. R. Dean Taylor

Prof. Moshe P. Pasternak, Tel Aviv University

L-R: R. Dean Taylor, Moshe Pasternak

History and Areas of Research

The story of Mössbauer spectroscopy (MS) at Los Alamos National Laboratory started with a big bang in early 1959, when the first report of Rudolf Mössbauer's discovery became known. Suddenly, about a dozen physicists, chemists, engineers, and theorists took their cafeteria discussions into the laboratory to (dis)prove this startling new development. Yes, such shifts in manpower were once possible without waiting for the proposal mill to grind away! But the LANL big bang suffered an exponential decay in manpower and funding shortly thereafter until today; the local efforts are carried on only by Dr. R. Dean Taylor, who actually "retired" in 1990, and Prof. Moshe Pasternak, Tel Aviv University, an enthusiastic collaborator since 1983, mostly through his annual summer visits to Los Alamos. Through the years a number of other collaborators, students, and post-docs have kept the research lively and exciting.

Some of the chronological LANL highlights and (principal collaborators) after our confirmation of Rudolf Mössbauer's 191Ir discovery and the first 67Zn MS experiment include:

  • Low temperature nuclear polarization (G. Dash)– 1960

  • Temperature dependence of 57Fe hyperfine field (D. Nagle, H. Frauenfelder) – 1960

  • MS using internal conversion x-rays (Frauenfelder) – 1961

  • Elliptical polarization of 57Fe gamma rays (Frauenfelder, W. Visscher ) – 1962

  • Local moments of dilute Fe in metals from (H, T) studies (T. Kitchens) – 1964-66

  • Absolute f-value lattice dynamics of 57Fe in metals (W. Steyert) – 1964

  • Hyperfine MS of 181Ta (Steyert) – 1965

  • Correlation between f-value and isomer shifts (P. Craig) – 1968

  • Kondo effect from MS studies (M. Maley) – 1970

  • MS thermometry below 0.1 K – 1972

  • Coexistence of magnetism and superconductivity (D. Erickson) – 1973-74

  • Magnetic field profiles of current-carrying tape superconductors from MS microprobes (A. Migliori) – 1976-77

  • Giant moments in Pd(Mn,Co) alloys (J. Willis) – 1980

  • Search for magnetism in e-iron at 220 kbar down to 20 mK and up to 47 kG – 1982

  • 151Eu pressure studies to 30 GPa in diamond anvil cells (J. Farrell) – 1986-88

  • 129I MS in I2, GeI4 and SnI4 molecular crystals to 30 GPa (M. Pasternak) – 1986-88

  • 109Ag MS and γ-ray lasers (G. Hoy) – 1988-92

  • 57Fe doped high-Tc superconductors (M. Smith) – 1990-94

  • Pressure-induced phase changes, amorphization, metallization, Mott transitions, spin order (Pasternak) – 1994-98

  • Diamond anvil cell development (Pasternak) – 1990-2001

  • Various 57Fe MS to 120 GPa (Pasternak) – 1997-2001

University of Delaware
Newark, Delaware

Names and Titles of Researchers

George C. Hadjipanayis, Professor
Evgueni Beloserov, Postdoctoral Scientist
Michael Bonder, Postdoctoral Scientist
Zhiqian Jin, Postdoctoral Scientist
Hideyuki Okumura, Postdoctoral Scientist
Vassil Skumryev, Postdoctoral Scientist
Stoyan Stoyanov, Postdoctoral Scientist
Wei Tang, Postdoctoral Scientist
Yong Zhang, Postdoctoral Scientist
Nadia Elwakil, Research Assistant
Sofoklis Makridis, Research Assistant
Maria Daniil, Graduate Student
Qian Dayou, Graduate Student
Yunhe Huang, Graduate Student
Hongli Wang, Graduate Student
Yushan Wang, Graduate Student
Zhicheng Yan, Graduate Student

George C. Hadjipanayis

Areas of Research

The Magnetics Laboratory of the Physics Department at the University of Delaware is currently working in the following areas of research:

  • Nanocomposite 2:14:1/α-Fe magnets. The purpose of this project is (1) to increase the energy product (at RT) of nanocomposite magnets based on R2Fe14B/α-Fe, R2Fe14B/α-Fe3B with R = Nd, Pr beyond 20 MGOe, and (2) to study the effect of carbon substitution for boron on the magnetic properties, crystal structure/microstructure, and crystallization behavior in the Nd-Fe-B system, and obtain nancomposite magnets based on the Nd2Fe14C phase.

  • Permanent Magnets. The group's objectives are to develop new classes of permanent magnets with dramatically improved properties by means of new preparation and characterization techniques, and state-of-the-art theoretical guidance. Studies are focused on (1) anisotropic nanocomposite 2:14:1/α-(FeCo), 1:5/FeCo, 2:17/FeCo and on precipitation hardened Fe(Co)-rich R-Fe(Co)-M materials; (2) Sm(Co-Fe-Cu-Zr)z and Nd-Fe-B magnets. The goals of these studies are (1) to produce a next generation permanent magnet with up to twofold increase in room temperature maximum energy product, and (2) to obtain energy products near their maximum theoretical values and improve dramatically temperature stability in existing commercially available magnets.

  • Nanoparticles. The nanoparticle research effort in the lab is twofold – it looks to advance the storage density limits of magnetic recording media as well as study the fundamental properties of magnetic materials as the size is reduced to critical limits. Coercivity mechanisms are of particular interest. By utilizing a novel, sputtering based deposition technique, samples of varying particle size can be made with a narrow particle size distribution. Materials of interest include the rare-earth metals, intermetallic compounds, and high anisotropy transition metal based alloys.

Collaborations include:

  • Materials Research Analysis, University of Nebraska, USA (Prof. D.J. Sellmyer)

  • Seagate Technology, Pittsburgh, USA (Dc. D. Weller)

  • Department of Physics, University of Ioannina, Greece (Prof. V. Papaefthymiou)

  • NCSR Demokritos, Institute of Materials Science, Aghia Paraskevi, Attikis, Greece (Dc. T. Simopoulos)

Duquesne University
Pittsburgh, Pennsylvania

Names and Titles of Researchers

Dr. Monica Sorescu, Assistant Professor
Dr. Agnes Grabias, Postdoctoral Researcher
Thomas Oberst, Graduate Student
Kevin Gossett, Graduate Student
Annalia Palumbo, Graduate Student
Adam Weber, Graduate Student
Alexis Zywan, Graduate Student

Areas of Research

The work at Duquesne University is being sponsored by the National Science Foundation and is focused on the following projects:

  • laser-induced magnetic anisotropy;

  • laser-induced crystallization in metallic glasses;

  • laser-induced amorphization of partially-ordered systems;

  • pulsed laser deposition of magnetic thin films and multilayers;

  • synthesis and properties of iron oxide nanoparticles;

  • symmetry and hyperfine fields in intermetallic compounds.

California Institute of Technology
Pasadena, California

Names and Titles of Researchers

Brent Fultz, Professor of Materials Science

Alan Yue, Graduate Student in Materials Science

Jiao Lin, Graduate Student in Materials Science

Alex Papandrew, Graduate Student in Materials Science

Brent Fultz troubleshooting electrical ground problems in an earlier version of Caltech’s Mössbauer spectrometer.

Itzhak Halevy and Alan Yue on a winter morning walk to the Mössbauer beamline at the Advanced Photon Source in Argonne (in background).

Areas of Research

For over 40 years, almost all applications of the Mössbauer effect have utilized its capabilities as a spectroscopy. The group at the California Institute of Technology uses such conventional Mössbauer spectrometry for measurements of local chemistry in ferromagnetic bcc Fe alloys. Most of the group’s work, however, involves two unconventional aspects of nuclear γ-ray resonance spectroscopy:

Mössbauer scattering can be coherent, enabling its use for diffraction experiments on materials. Hyperfine fields give Mössbauer diffraction a unique chemical environment selectivity not available with the other three methods of diffraction on materials (x-ray, electron, and neutron diffraction). The group uses the chemical selectivity of Mössbauer spectrometry to select an atom in a particular chemical environment, and measure a diffraction pattern from atoms having that particular environment.

In the last couple of years, advances at third-generation synchrotron sources have made it possible to measure nuclear excitations accompanied by phonon creation or annihilation. These inelastic spectra can be used to obtain the phonon partial densities of states of Fe atoms in materials. The group used such measurements to learn that the vibrational entropy of Fe3Al and Pt3Fe depends almost entirely on chemical short-range order (as opposed to long-range order). More recently, they have begun to measure phonon spectra in Fe alloys in diamond-anvil cells.

Frequent external collaborators include Dr. Itzhak Halevy (Israel), Dr. Gerard LeCaër (France), and Drs. E. E. Alp and W. Sturhahn (USA).

Drexel University
Philadelphia, Pennsylvania

Names and Titles of Researchers

Amar Nath, Professor Vladimir Chechersky, Senior Research Associate

Areas of Research

  • Novel Mechanism of Energy Transport. Conjugated molecules and other systems with delocalized electrons incorporating 57Co escape fragmentation when several tens of electron volt energy is deposited as a result of charge neutralization following the Auger event. The energy deposited on the molecule goes to excite delocalized electrons collectively. The plasmon decays in < 10-14 sec transferring practically all its energy to a single electron which is emitted.

  • Some Outstanding Problems in High Temperature Superconductivity. Emission Mössbauer studies show that the oxygen ions in the Cu-O chain oscillate between double-well potential wells on either side. We explored the cause of the deleterious effect on superconductivity of Pr substitution for Y. We also showed that the presence of a minuscule amount of extraneous O2 results in localization of static magnetic order with superparamagnetic behavior in the electron-doped superconductor, Nd2-xCexO4.

  • Emission Mössbauer Studies of Mixed Valence Manganites. Emission Mössbauer studies of mixed valence manganites indicate that small magnetic clusters are formed near the Curie temperature exhibiting superparamagnetic-like behavior. These clusters coalesce to form larger ones upon application of an external magnetic field and are responsible for observation of colossal magnetoresistivity.

Purdue University
West Lafayette, Indiana

Names and Titles of Researchers

Dr. James G. Mullen
Dr. C. K. Shepard
Dr. Scott N. Dickson

Areas of Research

The group's most recent work has focused on measuring the Debye-Waller factor in alkali halides and fcc metals, using super sources of 183Ta. The group has also carried out some measurements of lead alloyed with tin using conventional 119Sn sources.

One of the most interesting results of these studies was the observation of a non spherical thermal cloud for the cubic alkali halides. This result was determined by measuring the reflections from (h00) planes and (nnn) planes and finding the (h00) reflections have a larger amplitude of oscillation. In the three cases studied (NaCl, KCl, and KBr), the Debye-Waller factor for the (nnn) reflections was 14% greater than found for the (h00) reflections. It is generally accepted that the thermal cloud for cubic crystals with inversion symmetry, like NaCl, is isotropic. The group's result shows that the thermal cloud is not ellipsoidal as crystallographers have believed.

University of Maryland
College Park, Maryland

Name of Researcher

Dr. Satish B. Ogale

Areas of Research

Dr. Ogale does Mössbauer spectroscopy with collaborators in France (Prof. Béatrice Hannoyer in Rouen and Prof. Gilbert Marest in Lyon). With his French collaborators, he has been doing work on magnetic oxides of the perovskite type exhibiting colossal magnetoresistance effect. They include Fe dopant into a manganite and examine hyperfine interactions. They have also been studying other oxides, such as Fe3O4, Sr2FeReO6, Ba2FeReO6, Ca2FeReO6, Sr2FeMoO6, etc.

Colorado School of Mines
Golden, Colorado

Name and Title of Researcher

Don L. Williamson, Emeritus Professor of Physics

A more recent (2001) photo of Don in the Structure of Materials Lab, Colorado School of Mines.
Don Williamson and his first graduate student, M. Ellid, in 1976. The photo was taken in the Mössbauer spectroscopy lab at the Colorado School of Mines. M. Allid is now a professor in Tripoli, Libya.

History and Areas of Research

Don L. Williamson is the person in charge of the Mössbauer spectroscopy lab at the Colorado School of Mines (CSM). Although formally retired in August 2000 after 25 years in the Physics Department at CSM, the last five as Head of the Department, he continues collaborations with various faculty, students, and nearby scientists as research problems arise in the general area of materials science. Below is a list of recent Mössbauer spectroscopy collaborators:

  • Paul Wilbur, Professor of Mechanical Engineering, Colorado State University, Fort Collins, Colorado

  • Timothy Coutts, Senior Scientist, National Renewable Energy Laboratory (NREL), Golden, Colorado

  • David Young, Staff Scientist, NREL (former CSM Ph.D. Student)

  • Scott Rudge, FeRx Inc., Aurora, CO

The Mössbauer spectroscopy lab in the Physics Department at CSM also houses x-ray diffraction and small-angle x-ray scattering equipment and is known as the "Structure of Materials Lab." The research currently taking place is in three areas:

  • Surface modification of metals and alloys with high-flux, low-energy ion beams. Complementary CEMS, CXMS, and x-ray diffraction studies define the near-surface structures of these materials and help understand the mechanisms for improved wear and corrosion resistance, as well as unusual magnetic behavior. Extremely high concentrations of N can be introduced into solid solution of fcc stainless steels.

  • Structure of thin-film transparent conducting oxides. Optically transparent and electrically conducting oxide (TCO) thin films are finding wide-spread application as transparent electrodes for solar cells and flat panel displays as well as infrared-reflecting, low-emissivity architectural windows. Correlations of electrical and optical properties with structural properties determined by conversion-electron Mössbauer spectroscopy and x-ray diffraction (e.g., Sn oxidation state, Sn site disorder, degree of inversion in spinel structure) can help uncover mechanisms for improvement of these materials.

  • Magnetic Fe-C Nanocrystalline Powders for Drug Transport. Transport of chemotherapy drugs via magnetic transport is an emerging area in biomaterials research. Composite nanocrystalline Fe-C powders prepared by mechanical attrition are being characterized by a variety of techniques including Mössbauer spectroscopy in collaboration with a local biomedical company. Of interest are the fractions of interfacial/surface Fe sites and the sensitivity of the material to oxidation.

Northwestern University
Evanston, Illinois

Don Ellis

Oliver Warschkow

Jiang Ming

Names and Titles of Researchers

Don Ellis, Professor
Oliver Warschkow, Postdoctoral Scientist
Jiang Ming, Postdoctoral Scientist
Zenong Ding, Graduate Student
XiWen Wang, Graduate Student
Bin Deng, Graduate Student

Areas of Research

The Materials Theory Group in the Department of Physics and Astronomy at Northwestern University studies electronic, structural, and transport properties of materials using atomistic simulations and first-principle electronic structure theory. Current problems range from grain boundaries in crystals, to macromolecules, to ionic conductors, to catalysts…. The group's current Mössbauer-related projects include (1) hydrogenase, (2) Fe substitution in hydroxyapatite, and (3) transparent conductor In2-xSnxO3. For additional information about the group, please consult its Web site at <http://dvworld.nwu.edu>.

University of Arizona
Tucson, Arizona

Name and Title of Researcher

F. Ann Walker, Regents Professor–Department of Chemistry and Joint Professor–Department of Biochemistry and Molecular Biophysics

Areas of Research

The Mössbauer spectroscopy for the University of Arizona is being done in Germany (Lübeck) by Alfred Trautwein and his coworkers. All of the work has to do with low-spin Fe(III) and Fe(II) heme centers, where we are learning about the electron configuration of the metal as a function of the axial ligands and the macrocycle structure (porphyrins and hydroporphyrins), and about metal-ligand covalency. One additional project has to do with iron corroles, which we have formulated as S=3/2 Fe(III)-corrolate(2-) radical species. Magnetic susceptibility measurements on the latter complexes are also in progress.

The Catholic University of America
Washington, DC

Names and Titles of Researchers

Mössbauer Spectroscopy Institute – Department of Chemistry
Leopold May, Professor Emeritus of Chemistry

Vitreous State Laboratory – Department of Physics

Isabelle S. Muller, Project Manager and Adjunct Assistant Professor of Physics

Charles Viragh, Research Scientist

Elizabeth Rielley, Staff and Physics Graduate Student

L-R: Charles Viragh, Isabelle S. Muller, and Elizabeth Rielley

Areas of Research

Mössbauer Spectroscopy Institute
The research effort of the Institute has been devoted to the interpretation of Mössbauer spectroscopic measurements on a variety of chemical systems, including iron metal complexes, both inorganic and biochemicals, organotin compounds, metal complexes, minerals and alloys. One current project is concerned with tributyltin and triphenyltin compounds that are used in antifouling paints on ships and are poisons to many forms of sea life. The fates of these tin compounds in an aquatic environment are not completely understood, so in conjunction with Dr. George Eng, University of the District of Columbia, we have studied the speciation of these compounds in the sediments of the rivers in the vicinity of Washington and the Chesapeake Bay by measuring the spectra of the compounds directly within the sediments. This is now being extended to components of sediments, such as clays. Another project is the measurement of the ferrous and ferric composition of Indian pottery of the Americas and other ceramic materials.

Vitreous State Laboratory
Mössbauer spectroscopy is used at the Vitreous State Laboratory to characterize the redox state of iron in glasses. The glasses studied result from vitrification demonstration conducted on surrogates of radioactive wastes from the Hanford Department of Energy site in the State of Washington. Two research programs are using Mössbauer spectroscopy at this time. First, Mössbauer provides product monitoring of the glass melt produced in pilot demonstrations at scales of 10 kg to 1200 Kg of glass per day. As reductants are added to the high nitrate slurry feed to be vitrified, the Fe(II)/Fe(III) ratio in the melt provides a reliable indicator of the "oxygen vacancies." The use of sucrose as a reductant efficiently controls the violent foaming that can otherwise take place in the melt as a result of the nitrate decomposition in a more oxidizing melt. However, if the glass melt is too reducing (Fe2+/Fetot. > ~10%), other waste metallic components can be excessively reduced causing metallic precipitation in the melter. Mössbauer spectroscopy is also used in a study looking to optimize the currently low solubility of sulfate in glass (typically less than 0.5wt% as SO3). Again, iron is used as a redox indicator in the various glass formulations. Sulfate is added either as sodium sulfate in the batch or by bubbling a mixture of O2/SO2 in the melt. The redox potential is adjusted by bubbling a mixture of CO/CO2 in addition to SO2. The fraction of reduced iron has been spanned from 0 to 82% Fe2+/Fetot. The sulfur sites will be later characterized by EXAFS of these glass samples. The solubility of the various sulfur redox state will be examined.

Mount Holyoke College
South Hadley, Massachusetts

Name and Title of Researcher

Dr. (Melinda) Darby Dyar, Director

Areas of Research

The Mineral Spectroscopy Laboratory, Departments of Physics, Astronomy, and Earth and Environment, is a NASA- and NSF-funded laboratory that supports 57Fe studies of the valence state and site occupancy of Fe in geologic materials from terrestrial and extraterrestrial sources. Equipment includes a WEB Research Co. Mössbauer spectrometer with a Janis Research Co. Model 850 closed cycle He refrigerator. The research group includes undergraduate students from Mount Holyoke, Smith, Amherst, and Smith Colleges, as well as graduate students from the University of Massachusetts. Recent research topics include:

  • identification of asbestos minerals

  • complete chemical characterization of tourmaline

  • crystal chemistry of Fe in amphibole

  • ferric iron in sheet silicates as a function of assemblage

  • ferric iron and dehydrogenation in mantle phases (olivine, pyroxene, spinel, hornblende)

  • ferric iron in feldspar as a record of magmatic oxygen fugacity

  • oxidation states recorded in Martian and eucritic meteorites

  • phase indentification in Martian soil analogs

  • reference spectra for Martian landers

  • oxidation states in lunar and lunar-analog minerals

  • determination of recoil-free fractions in important rock-forming silicates

  • development of standards for synchrotron micro-XANES determinations of ferric iron

The lab is also developing a Web site for Mössbauer spectroscopy, optical, and infrared spectroscopy of extraterrestrial minerals (http://www.mtholyoke.edu/courses/mdyar/marsmins/index.shtml), and providing reference spectra to the Mineral Spectroscopy Web site at Caltech (http://minerals.gps.caltech.edu/).

Morgan State University
Baltimore, Maryland

Names and Titles of Researchers

Dr. Frederick W. Oliver, Laboratory Director, Professor of Physics
Dr. Eugene J. Hoffman, Assistant Professor of Physics
Dr. Dereje Seifu, Assistant Professor of Physics

Areas of Research

The Mössbauer Spectroscopy Laboratory is associated with the Department of Physics at Morgan State University. Mössbauer investigations are conducted in several areas, including nuclear reactor materials, colossal magnetoresistance materials, meteorites, mechanical alloys, thin films, soils, coals, and materials of biomedical interest. The laboratory is well equipped with three Austin Science spectrometers, with one being used for conversion electron Mössbauer spectroscopy. Experiments are conducted using iron and europium Mössbauer isotopes. Two cryogenic refrigerators, one liquid helium dewar, and a furnace are available for performing experiments at various temperatures. Mössbauer collaborators include Dr. Leopold May of the Catholic University of America and Dr. Clive Wynter of Nassau Community College.

This site is supervised by Mössbauer Effect Data Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China. Contact email: medc@dicp.ac.cn