Iodine molecule for neutrino mass spectroscopy: ab initio calculation of spectral rate

It has recently been argued that atoms and molecules may become good targets for determining neutrino parameters still undetermined, if the atomic/molecular process is enhanced by a new kind of coherence. We compute the photon energy spectrum rate arising from coherent radiative neutrino pair emission processes of metastable excited states of and its isovalent molecules, and , with an IR photon and the th neutrino mass eigenstates, and show how fundamental neutrino parameters may be determined. Energies of electronically excited states of , including the effect of spinorbit couplings, were calculated by the multiconfigurational second-order perturbation (CASPT2) method. Summation over many vibrational levels of intermediate states is fully incorporated. Unlike atomic candidates with a much larger energy difference, such as Xe, transitions from a vibrational level to give us an opportunity to determine the mass type (Majorana vs Dirac distinction) and the Majorana CPV (charge-conjugation parity violating) phases, although the rate is much smaller