Cholesteric liquid crystals (CLC) possess a characteristic handedness that causes right and left circularly polarized waves to propagate with different group velocities. According to the nature of the used liquid crystal one of the two modes of propagation can experience an almost zero group velocity which yields a high density of modes in the vicinity of the edges of the stop-bands where this mode density becomes null. The other mode is unaffected by the structure and behaves as in free space. These features have a consequence on the spontaneous emission process of an atom introduced as a dopant in such a medium which depends on the mode structure of the surrounding environment. We present here a theoretical description of the spontaneous emission of atoms in a CLC by introducing two different photon reservoirs corresponding to the two different modes of propagation. These elements of theory are shown to be applicable to the case of a Eu (thenoyltrifluoroacetonate)-(TTA)(3) (cholesteryl myristate (M) or pelargonate (P)) complex mixed with a CLC, the selective reflection band of which has been tuned to the mean wavelength of the D-5(0)-->F-7(2) transition of the emission spectrum of the Eu3+ ion. References: 38
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