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The Kramers-Heisenberg dispersion formula is an expression for the cross section for scattering of a photon by an atomic electron. It was derived before the advent of quantum mechanics by Hendrik Kramers and Werner Heisenberg in 1925, based on the correspondence principle applied to the classical dispersion formula for light. The quantum mechanical derivation was given by Paul Dirac in 1927. The Kramers–Heisenberg formula was an important achievement when it was published, explaining the notion of "negative absorption" (stimulated emission), the Thomas-Reiche-Kuhn sum rule, and inelastic scattering - where the energy of the scattered photon may be larger or smaller than that of the incident photon - thereby anticipating the Raman effect. == Equation == The Kramers-Heisenberg (KH) formula for second order processes is 〔〔J.J. Sakurai, Advanced Quantum Mechanics, Addison-Wesley (1967), page 56.〕 It represents the probability of the emission of photons of energy in the solid angle (centred in the direction), after the excitation of the system with photons of energy . are the initial, intermediate and final states of the system with energy respectively; the delta function ensures the energy conservation during the whole process. is the relevant transition operator. is the instrinsic linewidth of the intermediate state. 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「Kramers–Heisenberg formula」の詳細全文を読む スポンサード リンク
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