Resolved fluorescence spectra of NiH. Electronic structure,electronic energy transfer,and the Zeeman effect in low-lying states

Fourier transform spectra of collisionally induced fluorescence following isotopically selective laser excitation of NiH at ～550?nm have located an excited Ω?=?1/2 state of NiH lying 17900?cm^?1 above the electronic ground state. This is identified as v?=?0 of a ²Π_1/2 state originating from an Ni⁺ 3d⁸4s^{1 2}F configuration. Emission from this Ω′?=?1/2 state occurs predominantly to v″?=?0 and 1 of the ²Σ⁺ and W₂ ²Π_1/2 ligand field states, locating elusive f parity levels of W₂ ²Π_1/2 up to 5600?cm^?1 above the first rotational level of the electronic ground state, X ₁ ²Δ_5/2. Collisionally induced fluorescence following laser excitation at lower energies has also been recorded in the presence of a magnetic field (0.7–1?T), at Doppler limited resolution. Effective Landé factors g _J for rotational levels of the v?=?0 and 1 levels of the low-lying Ω″?=?5/2 and 3/2 components of the ²Δ and ²Π states of NiH have been derived from partially resolved Zeeman patterns. About 1600 transitions recorded in field-free conditions have been reduced to term energies relative to the lowest level of the ground state. They confirm strong spin-orbit mixing between the low-lying ligand-field states.