輻射減衰とスペクトル線幅 : Van VleckとSlaterの研究を中心に

概要

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The damping force introduced in the electron theory lost its place in Bohr's quantum theory, because Bohr ignored the radiation damping for the sake of the stability of the stationary state. Since the spontaneous emission gives rise to in the absence of external causes, it was difficult to handle the spontaneous emission with the perturbation method which premises the external disturbance. Nevertheless, by regarding the "abridged" radiation force (obtained by retaining only a term of the combination overtone asymptotically corresponding to the spectroscopic frequency) due to the electron's own radiation force as a perturbation, Van Vleck could show that the abridged radiation force, not the conventional damping force, should be considerd as the cause of the spontaneous emission in the old quantum theory. Slater's work was one of the first attempts to connect the mean lifetime of stasionary states with the spectral line breadth. According to the theory of Fourier analysis, a finite wave train emitted in a length of time has a frequency width Δv=1/Δt. Bohr considered that Δt was the duration of a transition process, whereas Slater regarded Δt as the mean lifetime of the stationary state in which the virtual oscillators continuously absorb and emit the virtual fields. Based on this assumption he derived the dispersion formula including the width of spectral lines.
日本科学史学会の論文
1992-09-22