External Radiation Assistance of Neutrinoless Double Electron Capture

The influence of electromagnetic radiation on nuclear processes is applied to an example of a neutrinoless double electron capture (0 nu 2ec). For cases with X-ray free-electron lasers (X-ray FELs) and/or inverse Compton X-ray sources, it was shown that such a decay can be significantly enhanced by tuning the system to the resonant conditions through the absorption and/or emission of a photon with the decay resonance defect energy Delta. In this case, the 0v2ec decay rate Gamma(2e) of nuclide Z grew linearly with field intensity (S/S-z) up to the X-ray flux power S-m similar to Z(6), while S-z similar to Z(6) (Gamma/Delta)(2) with decay width Gamma of a daughter atom. For the case of Kr-78 -> Se-78 - 0 nu 2eL(1)L(1) capture we find S-z similar to 10(9) W cm(-2) and S-m similar to 10(17) W cm(-2) which indicate a possibility of increasing decay rate to eight orders of magnitude or even larger.