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The Stark effect is the shifting and splitting of spectral lines of atoms and molecules due to presence of an external electric field. The amount of splitting or shifting is called the Stark splitting or Stark shift. In general, one distinguishes first- and second-order Stark effects. The first-order effect is linear in the applied electric field, while the second-order effect is quadratic in the field. The Stark effect is responsible for the pressure broadening (Stark broadening) of spectral lines by charged particles. When the split/shifted lines appear in absorption, the effect is called the inverse Stark effect. The Stark effect is the electric analogue of the Zeeman effect where a spectral line is split into several components due to the presence of a magnetic field. The Stark effect can be explained with fully quantum-mechanical approaches, but it has also been a fertile testing ground for semiclassical methods. ==History== The effect is named after Johannes Stark, who discovered it in 1913. It was independently discovered in the same year by the Italian physicist Antonino Lo Surdo, and in Italy it is thus sometimes called the Stark-Lo Surdo effect. The discovery of this effect contributed importantly to the development of quantum theory. Inspired by the magnetic Zeeman effect, and especially by Lorentz's explanation of it, Woldemar Voigt〔W. Voigt, ''Ueber das Elektrische Analogon des Zeemaneffectes'' (On the electric analogue of the Zeeman effect), Annalen der Physik, vol. 309, pp. 197-208 (1901).〕 performed classical mechanical calculations of quasi-elastically bound electrons in an electric field. By using experimental indices of refraction he gave an estimate of the Stark splittings. This estimate was a few orders of magnitude too low. Not deterred by this prediction, Stark〔J. Stark, ''Beobachtungen über den Effekt des elektrischen Feldes auf Spektrallinien I. Quereffekt'' (Observations of the effect of the electric field on spectral lines I. Transverse effect), Annalen der Physik, vol. 43, pp. 965-983 (1914). Published earlier (1913) in Sitzungsberichten der Kgl. Preuss. Akad. d. Wiss.〕 undertook measurements on excited states of the hydrogen atom and succeeded in observing splittings. By the use of the Bohr-Sommerfeld ("old") quantum theory Paul Epstein〔P. S. Epstein, ''Zur Theorie des Starkeffektes'', Annalen der Physik, vol. 50, pp. 489-520 (1916)〕 and Karl Schwarzschild〔K. Schwarzschild, Sitzungsberichten der Kgl. Preuss. Akad. d. Wiss. April 1916, p. 548〕 were independently able to derive equations for the linear and quadratic Stark effect in hydrogen. Four years later, Hendrik Kramers〔H. A. Kramers, Roy. Danish Academy, ''Intensities of Spectral Lines. On the Application of the Quantum Theory to the Problem of Relative Intensities of the Components of the Fine Structure and of the Stark Effect of the Lines of the Hydrogen Spectrum'', p. 287 (1919);''Über den Einfluß eines elektrischen Feldes auf die Feinstruktur der Wasserstofflinien'' (On the influence of an electric field on the fine structure of hydrogen lines), Zeitschrift für Physik, vol. 3, pp. 199-223 (1920)〕 derived formulas for intensities of spectral transitions. Kramers also included the effect of fine structure, which includes corrections for relativistic kinetic energy and coupling between electron spin and orbit. The first quantum mechanical treatment (in the framework of Heisenberg's matrix mechanics) was by Wolfgang Pauli.〔W. Pauli, ''Über dass Wasserstoffspektrum vom Standpunkt der neuen Quantenmechanik'' (On the hydrogen spectrum from the point of view of the new quantum mechanics). Zeitschrift für Physik, vol. 36 p. 336 (1926)〕 Erwin Schrödinger discussed at length the Stark effect in his third paper〔E. Schrödinger, ''Quantisierung als Eigenwertproblem'', Annalen der Physik, vol. 385 Issue 13, 437-490 (1926)〕 on quantum theory (in which he introduced his perturbation theory), once in the manner of the 1916 work of Epstein (but generalized from the old to the new quantum theory) and once by his (first-order) perturbation approach. Finally, Epstein〔P. S. Epstein, ''The Stark Effect from the Point of View of Schroedinger's Quantum Theory'', Physical Review, vol 28, pp. 695-710 (1926)〕 reconsidered the linear and quadratic Stark effect from the point of view of the new quantum theory. He derived equations for the line intensities which were a decided improvement over Kramers' results obtained by the old quantum theory. While first-order perturbation effects for the Stark effect in hydrogen are in agreement for the Bohr-Sommerfeld model and the quantum-mechanical theory of the atom, higher order effects are not. Measurements of the Stark effect under high field strengths confirmed the correctness of the quantum theory over the Bohr model. 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「Stark effect」の詳細全文を読む スポンサード リンク
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