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In spectroscopy, the Autler–Townes effect, named after American physicists Stanley Autler and Charles Townes, is a type of the dynamical (also known as AC) Stark effect, corresponding to the case when an oscillating electric field (e.g., that of a laser) is tuned in resonance (or close) to the transition frequency of a given spectral line, and resulting in a change of the shape of the absorption/emission spectra of that spectral line. It is the AC equivalent of the Stark effect which splits the spectral lines of atoms and molecules in a constant electric field. Compared to its DC counterpart, the fields in the AC effect are typically much larger, and the effects are harder to predict.〔Delone, Nikolai Borisovich, and Vladimir Pavlovich Krainov. "AC Stark shift of atomic energy levels." Physics-Uspekhi 42.7 (1999): 669-687.〕 While generally referring to atomic spectral shifts due to AC fields at any (single) frequency, the effect is more pronounced when the field is tuned to the frequency of a natural two level transition.〔Schuda, F., C. R. Stroud Jr, and M. Hercher. "Observation of the resonant Stark effect at optical frequencies." Journal of Physics B: Atomic and Molecular Physics 7.7 (1974): L198.〕 In this case, the alternating field has the effect of splitting the two bare transition states into doublets or "dressed states" that are separated by the Rabi frequency.〔Fox, Mark. Quantum Optics: An Introduction: An Introduction. Vol. 15. Oxford university press, 2006.〕 This is commonly achieved by a laser tuned to (or near) the desired transition. This splitting results in a Rabi cycle or Rabi oscillation between bare states which are no longer energy eigenstates of the atom-field Hamiltonian.〔Barnett, Stephen, and Paul M. Radmore. Methods in theoretical quantum optics. Vol. 15. Oxford University Press, 2002.〕 The resulting fluorescence spectrum of an atom is known as a Mollow triplet. The AC stark splitting is integral to several other phenomena in quantum optics, such as Electromagnetically induced transparency and Sisyphus cooling. Vacuum Rabi oscillations have also been described as manifestation of the AC Stark effect from atomic coupling to the vacuum field.〔 ==History== The AC stark effect was discovered in 1955 by American physicists Stanley Autler and Charles Townes while at Columbia University and Lincoln Labs at the Massachusetts Institute of Technology. Before the availability of lasers, the AC Stark effect was observed with radio frequency sources. Autler and Townes' original observation of the effect used a radio frequency source tuned to 12.78 and 38.28 MHz, corresponding to the separation between two doublet microwave absorption lines of OCS.〔Autler, Stanley H., and C. H. Townes. "Stark effect in rapidly varying fields." Physical Review 100.2 (1955): 703.〕 The notion of quasi-energy in treating the general AC Stark effect was later developed by Nikishov and Ritis in 1964 and onward.〔Nikishov, A. I., and V. I. Ritus. QUANTUM PROCESSES IN THE FIELD OF A PLANE ELECTROMAGNETIC WAVE AND IN A CONSTANT FIELD. PART I. Lebedev Inst. of Physics, Moscow, 1964.〕〔Ritus, V. I. "Shift and splitting of atomic energy levels by the field of an electromagnetic wave." Sov. Phys. JETP 24 (1967): 1041-1044.〕〔Zel'Dovich, Ya B. "Scattering and emission of a quantum system in a strong electromagnetic wave." Physics-Uspekhi 16.3 (1973): 427-433.〕 This more general method of approaching the problem developed into the "dressed atom" model describing the interaction between lasers and atoms〔 Prior to the 1970s there were various conflicting predictions concerning the fluorescence spectra of atoms due to the AC Stark effect at optical frequencies. In 1974 the observation of Mollow triplets verified the form of the AC Stark effect using visible light.〔 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「Autler–Townes effect」の詳細全文を読む スポンサード リンク
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