Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University, Leninskie gory, Moscow 119991, Russia.
Nuclear Safety Institute of RAS, Bol'shaya Tulskaya 52, Moscow 115191, Russia.
Phys Rev Lett. 2018 Mar 23;120(12):122501. doi: 10.1103/PhysRevLett.120.122501.
The main decay channels of the anomalous low-energy 3/2^{+}(7.8±0.5 eV) isomeric level of the ^{229}Th nucleus, namely the γ emission and internal conversion, inside a dielectric sphere, dielectric thin film, and conducting spherical microcavity are investigated theoretically, taking into account the effect of media interfaces. It is shown that (1) the γ decay rate of the nuclear isomer inside a dielectric thin film and dielectric microsphere placed in a vacuum or in a metal cavity can decrease (increase) in dozen of times, (2) the γ activity of the distributed source as a function of time can be nonexponential, and (3) the metal cavity, whose size is of the order of the radiation wavelength, does not affect the probability of the internal conversion in ^{229}Th, because the virtual photon attenuates at much shorter distances and the reflected wave is very weak.
异常低能 3/2^{+}(7.8±0.5 eV)同质异能态的 ^{229}Th 原子核的主要衰变通道，即γ发射和内转换，在介电球体内、介电薄膜内和导电球形微腔体内进行了理论研究，考虑了介质界面的影响。结果表明：（1）放置在真空或金属腔体内的介电薄膜和介电微球内的核同质异能的γ衰变率可以减少（增加）数十倍；（2）作为时间函数的分布式源的γ活度可以是非指数的；（3）尺寸与辐射波长相当的金属腔不会影响 ^{229}Th 内转换的概率，因为虚拟光子在更短的距离衰减，反射波非常弱。
