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Condensed matter physics is the field of physics that deals with the macroscopic and microscopic physical properties of matter, especially the solid and liquid phases, that arise from electromagnetic forces between atoms and electrons. More generally, the subject deals with condensed phases of matter: systems of many constituents with strong interactions among them. More exotic condensed phases include the superconducting phase exhibited by certain materials at extremely low cryogenic temperatures, the ferromagnetic and antiferromagnetic phases of spins on crystal lattices of atoms, the Bose–Einstein condensates found in ultracold atomic systems, and liquid crystals. Condensed matter physicists seek to understand the behavior of these phases by experiments to measure various material properties, and by applying the physical laws of quantum mechanics, electromagnetism, statistical mechanics, and other physics theories to develop mathematical models and predict the properties of extremely large groups of atoms.
Spectroscopy is the field of study that measures and interprets electromagnetic spectrum. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum.
The Mössbauer effect, or recoilless nuclear resonance fluorescence, is a physical phenomenon discovered by Rudolf Mössbauer in 1958. It involves the resonant and recoil-free emission and absorption of gamma radiation by atomic nuclei bound in a solid. Its main application is in Mössbauer spectroscopy.
The nuclear Overhauser effect (NOE) is the transfer of nuclear spin polarization from one population of spin-active nuclei to another via cross-relaxation. A phenomenological definition of the NOE in nuclear magnetic resonance spectroscopy (NMR) is the change in the integrated intensity of one NMR resonance that occurs when another is saturated by irradiation with an RF field. The change in resonance intensity of a nucleus is a consequence of the nucleus being close in space to those directly affected by the RF perturbation.
In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate electronic energy levels and the resulting splittings in those electronic energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the nucleus and electron clouds.
Dynamic nuclear polarization (DNP) is one of several hyperpolarization methods developed to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy. While an essential analytical tool with applications in several fields, NMR’s low sensitivity poses major limitations to analyzing samples with low concentrations and limited masses and volumes. This low sensitivity is due to the relatively low nuclear gyromagnetic ratios (γn) of NMR active nuclei (1H, 13C, 15N, etc.) as well as the low natural abundance of certain nuclei. Several techniques have been developed to address this limitation, including hardware adjustments to NMR instruments and equipment (e.g., NMR tubes), improvements to data processing methods, and polarization transfer methods to NMR active nuclei in a sample—under which DNP falls.
In quantum mechanics, angular momentum coupling is the procedure of constructing eigenstates of total angular momentum out of eigenstates of separate angular momenta. For instance, the orbit and spin of a single particle can interact through spin–orbit interaction, in which case the complete physical picture must include spin–orbit coupling. Or two charged particles, each with a well-defined angular momentum, may interact by Coulomb forces, in which case coupling of the two one-particle angular momenta to a total angular momentum is a useful step in the solution of the two-particle Schrödinger equation. In both cases the separate angular momenta are no longer constants of motion, but the sum of the two angular momenta usually still is. Angular momentum coupling in atoms is of importance in atomic spectroscopy. Angular momentum coupling of electron spins is of importance in quantum chemistry. Also in the nuclear shell model angular momentum coupling is ubiquitous.
The nuclear magnetic moment is the magnetic moment of an atomic nucleus and arises from the spin of the protons and neutrons. It is mainly a magnetic dipole moment; the quadrupole moment does cause some small shifts in the hyperfine structure as well. All nuclei that have nonzero spin also have a nonzero magnetic moment and vice versa, although the connection between the two quantities is not straightforward or easy to calculate.
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique based on re-orientation of atomic nuclei with non-zero nuclear spins in an external magnetic field. This re-orientation occurs with absorption of electromagnetic radiation in the radio frequency region from roughly 4 to 900 MHz, which depends on the isotopic nature of the nucleus and increased proportionally to the strength of the external magnetic field. Notably, the resonance frequency of each NMR-active nucleus depends on its chemical environment. As a result, NMR spectra provide information about individual functional groups present in the sample, as well as about connections between nearby nuclei in the same molecule. As the NMR spectra are unique or highly characteristic to individual compounds and functional groups, NMR spectroscopy is one of the most important methods to identify molecular structures, particularly of organic compounds.
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Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer in 1958, consists of the nearly recoil-free emission and absorption of nuclear gamma rays in solids. The consequent nuclear spectroscopy method is exquisitely sensitive to small changes in the chemical environment of certain nuclei.
In nuclear chemistry and nuclear physics, J-couplings are mediated through chemical bonds connecting two spins. It is an indirect interaction between two nuclear spins that arises from hyperfine interactions between the nuclei and local electrons. In NMR spectroscopy, J-coupling contains information about relative bond distances and angles. Most importantly, J-coupling provides information on the connectivity of chemical bonds. It is responsible for the often complex splitting of resonance lines in the NMR spectra of fairly simple molecules.
Hans Frauenfelder was an American physicist and biophysicist notable for his discovery of perturbed angular correlation (PAC) in 1951. In the modern day, PAC spectroscopy is widely used in the study of condensed matter physics. Within biophysics, he is known for his experimental and theoretical research on the dynamical behavior of protein tertiary structure.
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. High-resolution nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI). The original application of NMR to condensed matter physics is nowadays mostly devoted to strongly correlated electron systems. It reveals large many-body couplings by fast broadband detection and should not be confused with solid state NMR, which aims at removing the effect of the same couplings by Magic Angle Spinning techniques.
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Nuclear orientation, in nuclear physics, is the directional ordering of an assembly of nuclear spins with respect to some axis in space. It is one of the nuclear spectroscopy methods.
Nuclear resonance vibrational spectroscopy is a synchrotron-based technique that probes vibrational energy levels. The technique, often called NRVS, is specific for samples that contain nuclei that respond to Mössbauer spectroscopy, most commonly iron. The method exploits the high resolution offered by synchrotron light sources, which enables the resolution of vibrational fine structure, especially those vibrations that are coupled to the position of the Fe centre(s). The method is popularly applied to problems in bioinorganic chemistry, materials science, and geophysics. A novel aspect of the method is the ability to determine the 3D-trajectory of iron atoms within vibrational modes, providing a unique appraisal of DFT-prediction accuracy. Other names for this method include nuclear inelastic scattering (NIS), nuclear inelastic absorption (NIA), nuclear resonant inelastic x-ray scattering (NRIXS), and phonon assisted Mössbauer effect.
Paramagnetic nuclear magnetic resonance spectroscopy refers to nuclear magnetic resonance (NMR) spectroscopy of paramagnetic compounds. Although most NMR measurements are conducted on diamagnetic compounds, paramagnetic samples are also amenable to analysis and give rise to special effects indicated by a wide chemical shift range and broadened signals. Paramagnetism diminishes the resolution of an NMR spectrum to the extent that coupling is rarely resolved. Nonetheless spectra of paramagnetic compounds provide insight into the bonding and structure of the sample. For example, the broadening of signals is compensated in part by the wide chemical shift range (often 200 ppm in 1H NMR). Since paramagnetism leads to shorter relaxation times (T1), the rate of spectral acquisition can be high.
The perturbed γ-γ angular correlation, PAC for short or PAC-Spectroscopy, is a method of nuclear solid-state physics with which magnetic and electric fields in crystal structures can be measured. In doing so, electrical field gradients and the Larmor frequency in magnetic fields as well as dynamic effects are determined. With this very sensitive method, which requires only about 10–1000 billion atoms of a radioactive isotope per measurement, material properties in the local structure, phase transitions, magnetism and diffusion can be investigated. The PAC method is related to nuclear magnetic resonance and the Mössbauer effect, but shows no signal attenuation at very high temperatures. Today only the time-differential perturbed angular correlation (TDPAC) is used.
The local structure is a term in nuclear spectroscopy that refers to the structure of the nearest neighbours around an atom in crystals and molecules. E.g. in crystals the atoms order in a regular fashion on wide ranges to form even gigantic highly ordered crystals. However, in reality, crystals are never perfect and have impurities or defects, which means that a foreign atom resides on a lattice site or in between lattice sites (interstitials). These small defects and impurities cannot be seen by methods such as X-ray diffraction or neutron diffraction, because these methods average in their nature of measurement over a large number of atoms and thus are insensitive to effects in local structure. Methods in nuclear spectroscopy use specific nuclei as probe. The nucleus of an atom is about 10,000 to 150,000 times smaller than the atom itself. It experiences the electric fields created by the atom's electrons that surround the nucleus. In addition, the electric fields created by neighbouring atoms also influence the fields that the nucleus experiences. The interactions between the nucleus and these fields are called hyperfine interactions that influence the nucleus' properties. The nucleus therefore becomes very sensitive to small changes in its hyperfine structure, which can be measured by methods of nuclear spectroscopy, such as e.g. nuclear magnetic resonance, Mössbauer spectroscopy, and perturbed angular correlation.
References
- ↑ Glascock, Michael (2013-11-01). "Nuclear Spectroscopy". Treatise on Geochemistry. pp. 273–290. doi:10.1016/B978-0-08-095975-7.01419-4. ISBN 9780080983004 . Retrieved 2019-12-08.
{{cite book}}:|website=ignored (help) - ↑ Garrett, P. E.; Rodríguez, T. R.; Varela, A. D.; Green, K. L.; Bangay, J.; Finlay, A.; Austin RAE; Ball, G. C.; Bandyopadhyay, D. S.; Bildstein, V.; Colosimo, S.; Cross, D. S.; Demand, G. A.; Finlay, P.; Garnsworthy, A. B.; Grinyer, G. F.; Hackman, G.; Jigmeddorj, B.; Jolie, J.; Kulp, W. D.; Leach, K. G.; Morton, A. C.; Orce, J. N.; Pearson, C. J.; Phillips, A. A.; Radich, A. J.; Rand, E. T.; Schumaker, M. A.; Svensson, C. E.; et al. (2019-10-03). "Synopsis: Nuclear Spectroscopy Reveals New Shapes of Excited Nuclei". Physical Review Letters. 123 (14). U.S.: American Physical Society: 142502. doi:10.1103/physrevlett.123.142502. PMID 31702191. S2CID 207934601.
- ↑ Nuclear condensed matter physics, Günter Schatz and Alois Weidinger, ISBN 978-0471954798
- ↑ Th. Wichert, N. Achtziger, H. Metzner, R. Sielemann: Perturbed angular correlation. In: G. Langouche (Hrsg.): Hyperfine Interactions of Defects in Semiconductors. Elsevier, Amsterdam 1992, ISBN 0-444-89134-X, S. 77.
- ↑ Methods in Physical Chemistry, Rolf Schäfer, Peter C. Schmidt, Print ISBN 9783527327454, Online ISBN 9783527636839, doi : 10.1002/9783527636839
- ↑ Garibaldi, F.; Hashimoto, O.; Lerose, J. J.; Markowitz, P.; Nakamura, S. N.; Reinhold, J.; Tang, L. (2011). "Hypernuclear Spectroscopy". Journal of Physics: Conference Series. 299 (1): 012013. Bibcode:2011JPhCS.299a2013G. doi: 10.1088/1742-6596/299/1/012013 .
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