Theoretical laser cooling feasibility study of ZrH molecule at the fine structure level

A theoretical electronic structure calculation of the ZrH molecule is conducted via ab initio Complete Active Space Self-Consistent Field and the Multireference Configuration Interaction with Davidson correction calculation (CASSCF/MRCI + Q). The adiabatic potential energy curves (PECs) for the 53 low-lying electronic states in the representations of 2s+1 Λ (+/−) and Ω (+/−) for ZrH molecule have been investigated along with the internuclear distance R e , the harmonic frequency ω e , the dipole moment μ, the rotational constant B e and the electronic transition energy with respect to the ground state T e . are calculated. By using the canonical function approach, the vibrational energy E v , the rotational constants B v , the centrifugal constants D v , and the turning points R min and R max have been calculated up to the vibrational level v = 18. Based on the investigated data, the Franck−Condon factors, the Einstein coefficient, the radiative lifetimes, and the vibrational branching ratio for the transitions X 2 Δ 3/2 - (1) 4 Φ 3/2 , X 2 Δ 3/2 - (1) 4 Φ 5/2 , X 2 Δ 3/2 - (1) 2 Π 3/2 have been calculated. The large value of the radiative lifetimes in (ms) for these transitions proves that this molecule is not a good candidate for direct laser cooling.