科研之友
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摘要
Detailed theoretical investigation and computer calculations on Cherenkov radiation (CR) by an electron bunch moving uniformly in Hermitian medium (CRH) with and without absorption are presented in the paper. The theory shows that in the CRH, not only the current density but also the charge density of the particle contribute to the Cherenkov radiation. It has been found that there are two modes in the CRH; in general, only one of them is radiative mode and another one is local field. The frequency area where both of these two modes are radiative modes simultaneously is studied. The comparison of the two modes is given in the paper and the relation of the existence of these two modes is improved. The comparison of the calculations shows that the radiation power of mode "o" is larger than that of mode "e." It indicates that the group velocity in the CRH is slower than the phase velocity. Detailed computer calculations are given in the paper, and some interesting physical phenomena of CR are revealed. The theory gives a simple physical interpretation of the inner fine structure of the CRH; it is concluded that the mechanism of the appearance of the inner fine structure of CR is that in a dispersive medium the group velocity is less than the phase velocity. Possible applications of this theory are also discussed.
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