Properties of NoO and YbO.

Bond dissociation energies (BDEs) and spectroscopic parameters for the ground states of YbO and NoO were calculated at the Brueckner doubles (BD(T)) level and for NoO at the coupled cluster CCSD(T) level based on the closed-shell configurations Yb²⁺(4f¹⁴)O^2-(2p⁶) and No²⁺(5f¹⁴)O^2-(2p⁶). For YbO, the BD(T) BDE (3.93 eV) and vibrational frequency (686.3 cm^-1) are consistent with the experiment; the BD(T) bond distance was 1.8492 Å, about 0.04 Å longer than the experiment. For NoO, the calculated BDEs are 3.07 eV (BD(T)) and 3.08 eV (CCSD(T)) and are expected to be good to ±3 kcal/mol (±0.13 eV). Potential energy curves (PECs) for the spin-orbit (Ω) states associated with the f¹³s¹ configurations of YbO and NoO were calculated at the SA-CASSCF/SO-CASPT2/aQ-DK level. PECs considering both the f¹³s¹ and f¹⁴ configurations were calculated at this level, as the ground states are expected to contain both configurations. Due to a bias in the SA-CASSCF to the f¹³s¹ configurations, the f¹⁴ configurations could not be properly described simultaneously with the f¹³s¹ ones. The natural population analysis based on the natural bond orbitals shows that YbO and NoO are quite ionic, with 5d orbitals being more important in YbO than the 6d orbitals in NoO.