Speaker
Description
Discussion of hypothetical dark matter and dark energy in the universe stimulates a great interest in the study of neutrinoless-double-beta decay and double-e capture by the nucleus. The latter process if observed could give an unambiguous proof of the Majorana nature of neutrino. At the same time,it is usually suppressed by many orders of magnitude due to its resonance character and the related Breit-Wigner factor. On the other hand, atomic resonances can be tuned [1] by means of externally applied laser field. Consider2e0ν L1L1 capture in 78Kr to the 2+ 2438-keV level of 78Se. Defect or resonance Δ= 6.87 keV. This excessive energy can be transferred to the field of a soft-X-ray laser source.Such a transfer is fulfilled by the 2s-2p3/2 mixed state formed in the field of the laser. Then the p electrons mix with the s holes formed in the 2e-capture. The amplitude of admixture is = eE<2p|r|2s>/δ, E being the laser strength, and e – the electron charge. δ= 6.65keVequals the difference of the 2p3/2-2s-levels and the energy of the laser photon ћωl, respectively.The calculated value of the matrix element <2p|r|2s> = 22 keV-1. Acceleration factor of 12 arises due to the presence of the 6p electrons together with the 2s holes. Supposing = 1, one finds E109 V/cm.Then the gain due to absence of the Breit-Wigner factor is (Δ/ (G/2))2 = (6.87 / 0.0038)2 = 2.8×106, where G = 7.6 eV is the total width of the 2s-2 state.As a result, the rate doubles already at E = 400 V/cm, or irradiation power P= 4×106 W/cm2.Such fields are availableat X-ray free-electron lasers, whose development have seen the rise during the last two decades, such as the gamma factory at CERN [2] or tunable soft X-ray sources, like Linac Coherent Light Source with gigawatt power [3], and others.
References
[1] F. F. Karpeshin. Prompt Nuclear Fission in Muonic Atoms and Resonance Conversion,
Saint Petersburg: «Nauka», 2006.
[2] D. Budker et al. Ann. Phys. (Berlin) 534, 2100284 (2022).
[3] Joseph Duris et al., Nature Photonics: www.nature.com/naturephotonics, DOI: https://doi.org/10.1038/s41566-019-0549-5.
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