  The process of collective de-excitation of atoms in a metastable level into
emission mode of a single photon plus a neutrino pair, called radiative
emission of neutrino pair (RENP), is sensitive to the absolute neutrino mass
scale, to the neutrino mass hierarchy and to the nature (Dirac or Majorana) of
massive neutrinos. We investigate how the indicated neutrino mass and mixing
observables can be determined from the measurement of the corresponding
continuous photon spectrum taking the example of a transition between specific
levels of the Yb atom. The possibility of determining the nature of massive
neutrinos and, if neutrinos are Majorana fermions, of obtaining information
about the Majorana phases in the neutrino mixing matrix, is analyzed in the
cases of normal hierarchical, inverted hierarchical and quasi-degenerate types
of neutrino mass spectrum. We find, in particular, that the sensitivity to the
nature of massive neutrinos depends critically on the atomic level energy
difference relevant in the RENP.
