Mössbauer antineutrinos: Recoilless resonant emission and absorption of electron antineutrinos

Abstract

Basic questions concerning phononless resonant capture of monoenergetic electron antineutrinos (Mössbauer antineutrinos) emitted in bound-state β-decay in the 3 H -3 He system are discussed. It is shown that lattice expansion and contraction after the transformation of the nucleus will drastically reduce the probability of phononless transitions and that various solid-state effects will cause large line broadening. As a possible alternative, the rare-earth system 163 Ho -163 Dy is favoured. Mössbauer-antineutrino experiments could be used to gain new and deep insights into several basic problems in neutrino physics.

Neutrino oscillations and uncertainty relations

“…Fortunately, conventional Mössbauer spectroscopy (with photons) gathered a wealth of information on the behavior of rare-earth systems in the past. Of particular interest is the 25.65 keV Mössbauer resonance in 161 Dy where an experimental linewidth of exp ≈ 5 × 10 −8 eV has been reached [31,33]. We will show in the following section that the 163 Ho-163 Dy system might be suitable to investigate the question concerning the different approaches to neutrino oscillations.…”

“…In addition, for a Mössbauer νe experiment it is mandatory that no phonons are excited in the lattice when the νe is emitted or absorbed, because only then a highly monochromatic νe radiation and the large cross section of the Mössbauer resonance of typically 10 −19 -10 −17 cm 2 can be achieved. However, it became apparent [29][30][31][32] that there exist several basic difficulties to observe Mössbauer νe with the system 3 H-3 He in the Nb metal. The main problem originates from lattice expansion and contraction processes.…”

“…They occur when the nuclear transformations (from 3 H to 3 He and from 3 He to 3 H) take place during which the νe is emitted or absorbed and can cause lattice excitations (phonons) which change the νe energy and thus destroy the Mössbauer resonance. It has been estimated that due to these lattice excitations, the probability for phononless emission and consecutive phononless capture of νe is ∼7 × 10 −8 which makes a real experiment with the 3 H-3 He system extremely difficult [29][30][31][32]. Another basic problem is caused by inhomogeneities in an imperfect lattice which directly influence the energy of the νe [29].…”

“…On the negative side, the magnetic moments of the 4f electrons of the rare-earth atoms are large and might cause broadening of the Mössbauer νe resonance [31,32]. Fortunately, conventional Mössbauer spectroscopy (with photons) gathered a wealth of information on the behavior of rare-earth systems in the past.…”

Fenomenologia De Neutrinos E Física Além Do Modelo Padrão

“…Neste caso, a energia doν eé determinada por: Como foi discutido na seção anterior, a transferência de momento no processo de emissão e absorção destrói a ressonância. Podemos estimar a fração f r sem recuo no processo de emissão e detecção usando a seguinte relação [97,98,102]: …”