An Introduction to Mössbauer Spectroscopy

The initial impetus for this text occurred when we were searching for a single book that could be recommended to the attendees at the Mossbauer Spectroscopy Institute at The Catholic University of America. This Institute is an introductory course on the theory and interpretation of Mossbauer spectroscopy for workers in industrial, academic, and government labora­ tories. None of the books available adequately covered the breadth and scope of the lectures in the Institute. A list of these books and review articles is included in Appendix C. To meet our needs, we undertook the creation of this text. The chapters are based upon the lectures given at the various Institutes from 1967 to 1969. Most of the lectures were recorded and transcripts sent to the lecturers, who then prepared the manuscripts, using the transcripts as a guide so as to retain the style developed during the lecture. Each chapter is written in the style of the authors. As the editor, my main task was to main­ tain uniformity of format and nomenclature. A list of nomenclature used in this volume is reproduced in Appendix A. We hope that this list will be used particularly by new investigators and teachers of Mossbauer spectroscopy so that future literature will employ a uniform system.

1 Introduction to the Mössbauer Effect.- 1. Pictorial Description.- 2. Background Concepts.- 2. 1. Natural Line Width.- 2. 2. Recoil Energy Loss.- 2. 3. Resonance and Resonance Fluorescence.- 2. 4. Doppler Broadening.- 2. 5. Einstein Solids.- 2. 6. Recoil-Free Emission of Gamma Rays.- 3. The Mössbauer Effect.- 3. 1. Pictorial Approach.- 3. 2. Observation of the Mössbauer Effect.- 4. Theory.- 2 Instrumentation.- 1. Instrumentation.- 1. 1. Gamma-Ray Detection.- 1. 2. Doppler Velocity Drive.- 2. Accuracy and Precision.- 2. 1. Calibration Methods.- 2. 2. Time of Counting.- 3. Experimental Techniques.- 3. 1. Sources.- 3. 2. Mössbauer Absorbers.- 3. 3. f-Factor Measurements.- 3. 4. Variable Temperature.- 3. 5. Scattering Methods.- 4. Applications of Computers to Mössbauer Spectra.- 4. 1. Computation of Mössbauer Spectra from a Theoretical Model.- 4. 2. Curve Fitting of Mössbauer Data by Least-Square Analysis.- 4. 3. Curve Fitting of Mössbauer Data by Constrained Least-Square Analysis.- 3 Nuclear Properties Determined from Mössbauer Measurements.- 1. A Phenomenological View of the Hyperfine Interactions.- 2. Differences in the Nuclear Charge Radius?R/R.- 2. 1. ?|?(0)|2 from “Pure Ionic” Valence States.- 2. 2. ?|?(0)|2 from Band Theory.- 2. 3. ?|?(0)|2 Caused by Overlap.- 2. 4. ?|?(0)|2 from the Shielding of p Holes.- 2. 5. ?R Ratios Method.- 2. 6. Nuclear Information from?R.- 3. Nuclear Quadrupole Moments Q and Spins I.- 3. 1. Quadrupole Moment Ratios Q*/Q.- 3. 2. Direct Determination of Quadrupole Moment Values.- 3. 3. Direct Determination of Nuclear Spins.- 4. Nuclear Magnetic Dipole Moments.- 5. Nuclear Lifetimes.- 6. Internal Conversion.- 7. Parity, Multipole Mixing, and Time Reversal.- 7. 1. Mössbauer Observation of Parity Nonconservation.- 7. 2. Multipole Mixing and Time Reversal.- 8. Nuclear Reactions and Devices.- 4 The Electric Field Gradient Tensor.- 1. The “Standard Form” EFG Tensor Due to a Single-Point Charge.- 2. The Ligand Contribution.- 3. The Valence Electron Contribution.- 4. Quadrupole Splittings.- 4. 1. The Nuclear Quadrupole Interaction.- 4. 2. Ligand-Only Splittings.- 4. 3. Valence-Only Splittings.- 4. 4. Ligand-Valence Combined Splittings.- 5. Potpourri.- 5. 1. Compounds with Internal Magnetic Fields.- 5. 2. Applied Magnetic Fields.- 5. 3. The Gol’danskii-Karyagin Effect.- 5. 4. Single Crystal Samples.- 6. The Utility of EFG Information.- Appendix I.- Appendix II.- 5 Application to Solid-State Physics.- 1. Isomer Shift.- 2. Magnetic Hyperfine Structure.- 3. Electric Quadrupole Interaction.- 4. Lattice Dynamics.- 6 Application to Coordination Chemistry.- 1. Crystalline Structure.- 2. Complex Isomerism.- 2. 1. Cis-Trans Isomerism.- 2. 2. Ligand Linkage Isomerism.- 2. 3. Spin-State Equilibria.- 3. Structure of Complicated Complex Compounds.- 4. Electronic Structure of Molecules.- 4. 1. Using Ligand Field Theory.- 4. 2. Using Molecular Orbital Theory.- 4. 3. Using the Spin Hamiltonian.- 7 Application to Organometallic Compounds.- 1. Isomer Shifts.- 1. 1. Organoiron Compounds.- 1. 2. Organotin Compounds.- 2. Quadrupole Splitting.- 2. 1. Organoiron Compounds.- 2. 2. Organotin Compounds.- 3. Conformational Studies.- 3. 1. Cyclooctatetraene Iron Tricarbonyl [COTFe(CO)3].- 3. 2. [?-C5H5Fe(CO)2]2 SnCl2 and Related Molecules.- 4. Conclusion.- 8 Mössbauer Spectroscopy and Physical Metallurgy.- 1. Mössbauer Application to Physical Metallurgy.- 1. 1. Precipitation in the Cu-Fe System.- 1. 2. Phase Transition in Stainless Steel.- 1. 3. Internal Oxidation Studies.- 1. 4. Magnetic Properties in Au-Fe Alloys.- 1. 5. Near-Neighbor Interaction in ?-Fe-Mo Alloys.- 1. 6. Near-Neighbor Interaction in Fe-C Alloys.- 1. 7. Order-Disorder in FeAl and Fc3Al.- 1. 8. Thin Films and Superparamagnetism.- 1. 9. Mössbauer Effect as a Nondestructive Analytical Tool.- 2. Physical Metallurgy Considerations Concerning the Mössbauer Effect.- 3. Summary.- 9 Application to Biochemical Systems.- 1. Hemoproteins.- 2. Experimental Conditions.- 2. 1. Enrichment.- 2. 2. Effect of Thickness.- 2. 3. State of the Absorber.- 3. Effect of Experimental Variables.- 3. 1. Effect of Temperature.- 3. 2. Effect of Magnetic Field.- 4. Spin-Spin Equilibrium.- Appendix A Nomenclature of Mössbauer Spectroscopy.- Appendix B Bibliographic Sources.- Appendix C Selected References on Mössbauer Spectroscopy.