Relativistic configuration interaction calculation on the ground and excited states of iridium monoxide

Abstract

We present the fully relativistic multi-reference configuration interaction calculations of the ground and lowlying excited electronic states of IrO for individual spin-orbit component. The lowest states for four spin-orbit components 1/2, 3/2, 5/2, and 7/2 are calculated intensively to clarify the ground state of IrO. Our calculation suggests that the ground state is of 1/2 spin-orbit component, which is highly mixed with 4 Σ − and 2 Π states in Λ − S notation. The two low-lying states of the 5/2 and 7/2 spin-orbit components are nearly degenerate with the ground state and locate only 234 and 260 cm −1 above, respectively. The equilibrium bond length 1.712Å and harmonic vibrational frequency 903 cm −1 of the 5/2 spin-orbit component are close to the experimental measurement of 1.724Å and 909 cm −1 , which suggests the 5/2 state should be the low-lying state contributed to spectra in experimental study. Moreover, the electronic states that give rise to the observed transition bands are assigned in terms of the excited energies and oscillator strengths obtained for the 5/2 and 7/2 spin-orbit components.

Electronic Structure of OsSi Calculated by MS-NEVPT2 with Inclusion of the Relativistic Effects

“…For the theoretical studies, the controversial results in different calculations and inconsistency with the experimental conclusion indicate OsC is more challenging than OsSi, thus higher level calculation such as the four-component multireference configuration interaction is desired to clarify the ground state of OsC as for the IrO molecule. 61 According to our data, two experimental transitions, namely A ← X 3 Σ 0 + − and B ← X 3 Σ 0 + − , can be assigned. 17 The A − X system should attribute to the 3 Π 1 (I) ← X 3 Σ 0 + − transition, in which the adiabatic excitation energy 15568 cm −1 agrees well with the experimental value of 15729 cm −1 .…”

“…Therefore, more experimental works are desired. For the theoretical studies, the controversial results in different calculations and inconsistency with the experimental conclusion indicate OsC is more challenging than OsSi, thus higher level calculation such as the four-component multireference configuration interaction is desired to clarify the ground state of OsC as for the IrO molecule …”