Accurate prediction of vibronic structure for a radium-containing laser-coolable molecule

Molecules containing radium possess large effective electric fields and thus are sensitive to the search of electron's electric dipole moment (eEDM). Furthermore, the radium isotopes with static octupole deformation can enhance the sensitivities for the measurements of Schiff moment. Laser cooling of radium-containing molecules plays an important role in enhancing the sensitivity in these measurements. The laser-coolability of the RaOH molecule has been studied using a multi-state vibronic model. The A²Π_1/2(000) to X²Σ_1/2(v₁v₂v₃) transitions in RaOH have quasidiagonal Franck-Condon factors with the origin transition accounting for 99% of the transition intensities and with only six transitions having branching ratios above 10^-5. Accurate transition energies have been calculated for the RaF and RaOH molecule. These calculations indicate that there is no intermediate state between A²Π_1/2 and X²Σ_1/2 in RaOH. RaOH thus is a very promising polyatomic radioactive molecule for laser cooling and for subsequent precision measurement search of new physics beyond the Standard Model.