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利用者:加藤勝憲/充実させるための翻訳（マイクロ波分光法）

マイクロ波分光法は、マイクロ波（GHz帯の電磁波）を物質の研究に用いる分光法である。

開発史[編集]

アンモニア分子NH3は、高さ0.38Åのピラミッド型で、水素の正三角形が底面を形成しています。軸上に位置する窒素は、水素の三角形の上下に2等分の平衡位置を持ち、このため、窒素は水素原子の平面を通って上下にトンネル移動する可能性を持っている。

The ammonia molecule NH3 is shaped like a pyramid 0.38 Å in height, with an equilateral triangle of hydrogens forming the base.The nitrogen situated on the axis has two equivalent equilibrium positions above and below the triangle of hydrogens, and this raises the possibility of the nitrogen tunneling up and down, through the plane of the H-atoms.

1932年、デビッド・M・デニソンらはこの分子の振動エネルギーを解析し、この2つの平衡位置の存在によって振動エネルギーが対に分割されると結論づけた。翌年、ライトとハリソン・M・ランドールは...遠赤外線において0.67cm-1の分裂を観測し、ν=20GHzに対応する、理論で予測される値を示した。

1934年、クロード・E・クリートンとニール・H・ウィリアムズは、この分裂を直接測定するためにグレーティング・エシェレット分光器を製作し、マイクロ波分光の分野を開始した。その結果、24GHzに最大、12GHzに半値幅を持つ、やや非対称な吸収線が観測された[1]。

分子物理学[編集]

  1. ^ Eaton, Gareth R.; Eaton, Sandra S.; Salikhov, Kev (1998). “Chapter A.2. Preparing the Way for Paramagnetic Resonance by Charles P. Poole, Jr. and Horacio A. Farach”. Foundations Of Modern EPR. pp. 13–24. ISBN 9789814496810. https://books.google.com/books?id=PBjtCgAAQBAJ&pg=PA15  (quote from p. 15 — Norman Wright worked for the Dow Chemical Company Physics Lab in Midland, Michigan. He was awarded the Pittsburgh Spectroscopy Award for 1958.)

In the field of molecular physics, microwave spectroscopy is commonly used to probe the rotation of molecules.[1]

物性物理学[編集]

In the field of condensed matter physics, microwave spectroscopy is used to detect dynamic phenomena of either charges or spins at GHz frequencies (corresponding to nanosecond time scales) and energy scales in the µeV regime. Matching to these energy scales, microwave spectroscopy on solids is often performed as a function of temperature (down to cryogenic regimes of a few K or even lower)[2] and/or magnetic field (with fields up to several T). Spectroscopy traditionally considers the frequency-dependent response of materials, and in the study of dielectrics microwave spectroscopy often covers a large frequency range. In contrast, for conductive samples as well as for magnetic resonance, experiments at a fixed frequency are common (using a highly sensitive microwave resonator),[3] but frequency-dependent measurements are also possible.[4]

Probing charges in condensed matter physics[編集]

For insulating materials (both solid and liquid),[5] probing charge dynamics with microwaves is a part of dielectric spectroscopy. Amongst the conductive materials, superconductors are a material class that is often studied with microwave spectroscopy, giving information about penetration depth (governed by the superconducting condensate),[3][6] energy gap (single-particle excitation of Cooper pairs), and quasiparticle dynamics.[7]

Another material class that has been studied using microwave spectroscopy at low temperatures are heavy fermion metals with Drude relaxation rates at GHz frequencies.[4]

Probing spins in condensed matter physics[編集]

Microwaves impinging on matter usually interact with charges as well as with spins (via electric and magnetic field components, respectively), with the charge response typically much stronger than the spin response. But in the case of magnetic resonance, spins can be directly probed using microwaves. For paramagnetic materials, this technique is called electron spin resonance (ESR) and for ferromagnetic materials ferromagnetic resonance (FMR).[8] In the paramagnetic case, such an experiment probes the Zeeman splitting, with a linear relation between the static external magnetic field and the frequency of the probing microwave field. A popular combination, as implemented in commercial X-band ESR spectrometers, is approximately 0.3 T (static field) and 10 GHz (microwave frequency) for a typical material with electron g-factor close to 2.

脚注[編集]

[[Category:超伝導]] [[Category:分子物理学]] [[Category:分光学]]

  1. ^ Gordy, W. (1970). A. Weissberger. ed. Microwave Molecular Spectra in Technique of Organic Chemistry. IX. New York: Interscience 
  2. ^ Krupka, J. (1999). “Complex permittivity of some ultralow loss dielectric crystals at cryogenic temperatures”. Meas. Sci. Technol. 10 (5): 387–392. Bibcode: 1999MeScT..10..387K. doi:10.1088/0957-0233/10/5/308etal 
  3. ^ a b Hardy, W. N. (1999). “Precision measurements of the temperature dependence of λ in YBa2Cu3O6.95: Strong evidence for nodes in the gap function”. Phys. Rev. Lett. 70 (25): 3999–4002. Bibcode: 1993PhRvL..70.3999H. doi:10.1103/PhysRevLett.70.3999. PMID 10054019etal 
  4. ^ a b Scheffler, M. (2013). “Microwave spectroscopy on heavy-fermion systems: Probing the dynamics of charges and magnetic moments”. Phys. Status Solidi B 250 (3): 439–449. arXiv:1303.5011. Bibcode: 2013PSSBR.250..439S. doi:10.1002/pssb.201200925etal 
  5. ^ Kaatze, U.; Feldman, Y. (2006). “Broadband dielectric spectrometry of liquids and biosystems”. Meas. Sci. Technol. 17 (2): R17–R35. Bibcode: 2006MeScT..17R..17K. doi:10.1088/0957-0233/17/2/R01. 
  6. ^ Hashimoto, K. (2009). “Microwave Penetration Depth and Quasiparticle Conductivity of PrFeAsO1−y Single Crystals: Evidence for a Full-Gap Superconductor”. Phys. Rev. Lett. 102 (1): 017002. arXiv:0806.3149. Bibcode: 2009PhRvL.102a7002H. doi:10.1103/PhysRevLett.102.017002. PMID 19257228etal 
  7. ^ Hosseini, A. (1999). “Microwave spectroscopy of thermally excited quasiparticles in YBa2Cu3O6.99”. Phys. Rev. B 60 (2): 1349–1359. arXiv:cond-mat/9811041. Bibcode: 1999PhRvB..60.1349H. doi:10.1103/PhysRevB.60.1349etal 
  8. ^ Farle, M. (1998). “Ferromagnetic resonance of ultrathin metallic layers”. Rep. Prog. Phys. 61 (7): 755–826. Bibcode: 1998RPPh...61..755F. doi:10.1088/0034-4885/61/7/001. 
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