Electronic structure of the ZnCl molecule with rovibrational and ionicity studies of the ZnX (X = F, Cl, Br, I) compounds

Based on the complete active space self consistent field (CASSCF) method with multi-reference configuration interaction MRCI calculations including single and double excitations with Davidson correction (+Q), twenty three low lying electronic states in the ^2s+1Λ^(±) representation of the zinc monochloride ZnCl molecule are investigated considering 7 and 9 valence electrons. The internuclear distance R_e, the harmonic frequency ω_e, the permanent dipole moment μ, the rotational constant B_e and the electronic transition energy with respect to the ground state T_e are calculated for the bound states. The transition dipole moment between some doublet states is used to determine the Einstein spontaneous A₂₁ and induced emission B21ω coefficients, the spontaneous radiative lifetime τ_spon, the emission wavelength λ₂₁, the oscillator strength f₂₁ and the line strength S₂₁. The fraction of the ground state ionic character f and equilibrium dissociation energy D_E,e are also computed. Using the canonical function approach, the eigenvalues E_v, the rotational constants B_v, the centrifugal distortion constants D_v and the abscissas of the turning points R_min and R_max of the zinc monohalide molecules ZnX (X: F, Cl, Br, I) are calculated. The comparison between the values of the present work and those available in the literature for several electronic states shows good accordance.