Laser spectroscopy of holmium oxide: Examination of the low-lying electronic states

Laser spectroscopy of holmium monosulphide: Electronic, vibrational and rotational structure of the A[14.79]8.5–X8.5, A[14.79]8.5–W[0.25]7.5 and A[14.79]8.5–V[0.98]7.5 transitions

“…The ground state X = 8.5 value was assigned to be the same as that of HoO which has the same ground state configuration. The pattern of a ground X = 8.5 and two low lying X = 7.5 states is the same as that observed for HoO [2].…”

“…Because of the effective shielding properties of the 4f orbitals, the vibration frequency is expected to be similar for all the lanthanide sulphide states with similar configurations, in this case f N s. For the oxides, we found that HoO, with a ground f 10 s configuration has a vibration frequency of $830 cm À1 [2] whereas that of YbO, with a closed shell f 14 configuration was $690 cm À1 [3]. For YbS, also with a f 14 ground configuration, the vibration frequency is $365 cm À1 [7].…”

“…The spectroscopy and structure of lanthanide oxides and halides has been the subject of many investigations in this and other laboratories [1][2][3][4][5]. In all cases, the properties and electronic structure could be understood in terms of a Ligand Field Theory (LFT) model in which the molecule is considered as ionically bound M 2+ O 2À or M + X À where M represents the lanthanide metal atom and X a halogen atom.…”

“…Several years ago, we reported on the laser spectroscopy of HoO in which we studied the vibrational, rotational and hyperfine structure of several transitions involving four low lying electronic states [2]. The observations of a ground X = 8.5 state, two low lying X = 7.5 and one X = 6.5 state were shown to be in accord with LFT predictions, with all the observed states arising from the Ho 2+ (4f 10 6s)O 2À configuration.…”

The permanent electric dipole moment of holmium monoxide, HoO

“…Unraveling the complex electronic spectra of simple lanthanide molecules, such as HoO [1,2], is particularly challenging because of the high density of low-lying states and large spin-orbit splitting and interactions. The near degeneracy of the multitude of states arising from the various arrangements of the electrons in the non-filled f-orbital is a consequence of the 4f orbitals being strongly contracted towards the nucleus and shielded by the outermost 5s and 5p closed shells from fields outside the atom [3].…”