Laser cooling of InF, InCl and InH with an ab initio study

The feasibility of laser cooling InF, InCl and InH is investigated based on ab initio quantum chemistry. To determine their suitability for laser cooling molecules, we have calculated the electronic structures, spectroscopic parameters, transition dipole moments (TDMs), radiative lifetimes, Franck–Condon factors (FCFs) and diode laser excitation wavelengths of InF, InCl and InH. Calculated spectroscopic constants of the first three electronic states for InF, InCl and InH show good agreement with available theoretical and experimental results. InF has highly diagonally distributed FCFs (f(00) = 0.961, f(11) = 0.909) for the C(1)Π → X(1)Σ(+) transition, and the rather short lifetime of the state C(1)Π is computed to be 2.77 ns at the lowest vibrational level. Notable is that the (3)Π → X(1)Σ(+) transition of InF also has large diagonal FCFs and short lifetimes. Therefore, InCl and InH are not potential laser-cooling candidates because the FCFs of the (1)Π → X(1)Σ(+) transition are off-diagonal. We further propose laser cooling schemes for InF. The present results could provide a promising theoretical reference for further theoretical and experimental research on InF, InCl and InH.