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Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer in 1957, consists in the recoil-free, resonant absorption and emission of gamma rays in solids. Like NMR spectroscopy, Mössbauer spectroscopy probes tiny changes in the energy levels of an atomic nucleus in response to its environment. Typically, three types of nuclear interactions may be observed: an isomeric shift, also known as a chemical shift; quadrupole splitting; and magnetic or hyperfine splitting, also known as the Zeeman effect. Due to the high energy and extremely narrow line widths of gamma rays, Mössbauer spectroscopy is a very sensitive technique in terms of energy (and hence frequency) resolution, capable of detecting change in just a few parts per 1011. ==Basic principle== (詳細はconservation of momentum requires a nucleus (such as in a gas) to recoil during emission or absorption of a gamma ray. If a nucleus at rest ''emits'' a gamma ray, the energy of the gamma ray is slightly ''less'' than the natural energy of the transition, but in order for a nucleus at rest to ''absorb'' a gamma ray, the gamma ray's energy must be slightly ''greater'' than the natural energy, because in both cases energy is lost to recoil. This means that nuclear resonance (emission and absorption of the same gamma ray by identical nuclei) is unobservable with free nuclei, because the shift in energy is too great and the emission and absorption spectra have no significant overlap. The recoil fraction of the Mössbauer absorption is analyzed by Nuclear resonance vibrational spectroscopy. Nuclei in a solid crystal, however, are not free to recoil because they are bound in place in the crystal lattice. When a nucleus in a solid emits or absorbs a gamma ray, some energy can still be lost as recoil energy, but in this case it always occurs in discrete packets called phonons (quantized vibrations of the crystal lattice). Any whole number of phonons can be emitted, including zero, which is known as a "recoil-free" event. In this case conservation of momentum is satisfied by the momentum of the crystal as a whole, so practically no energy is lost.〔International Board on the Applications of the Mössbauer Effect (IBAME) and Mössbauer Effect Data Center (MEDC), (Mössbauer Effect website ) Accessed June 3, 2010〕 Mössbauer found that a significant fraction of emission and absorption events will be recoil-free, which is quantified using the Lamb–Mössbauer factor.〔Gütlich, J.M.; (The Principle of the Mössbauer Effect and Basic Concepts of Mössbauer Spectrometry )〕 This fact is what makes Mössbauer spectroscopy possible, because it means gamma rays emitted by one nucleus can be resonantly absorbed by a sample containing nuclei of the same isotope, and this absorption can be measured. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mössbauer spectroscopy」の詳細全文を読む スポンサード リンク
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