I${}_2$ molecule for neutrino mass spectroscopy: ab initio calculation of spectral rate

Abstract

It has recently been argued that atoms and molecules may become good targets of determining neutrino parameters still undetermined, if atomic/molecular process is enhanced by a new kind of coherence. We compute photon energy spectrum rate arising from coherent radiative neutrino pair emission processes of metastable excited states of I${}_2$ and its iso-valent molecules, $|Av⟩\to |X{v}^{\prime }⟩+\gamma +{\nu }_i{\nu }_j$ and $|A^{\prime }v⟩\to |X{v}^{\prime }⟩+\gamma +{\nu }_i{\nu }_j$ with $\gamma$ an IR photon and ${\nu }_{i(j)}$ $i(j)-$th neutrino mass eigenstates, and show how fundamental neutrino parameters may be determined. Energies of electronically excited states of I${}_2$, including the effect of spin-orbit couplings were calculated by the multiconfigurational second order perturbation (CASPT2) method. Summation over many vibrational levels of intermediate states is fully incorporated. Unlike atomic candidate of a much larger energy difference such as Xe, I${}_2$ transitions from a vibrational level $A(v=0)$ to $X(v^{\prime }=24)$ give an opportunity of determination of the mass type (Majorana vs Dirac distinction) and determination of Majorana CPV (charge-conjugation parity violating) phases, although the rate is much smaller.

Comments: 24 pages, 19 figures