Spectroscopy of nickel chloride: Identification of the [15.0] 2Π3/2 and [15.0] 2Δ5/2 states

Vibrational bands belonging to the [15.0] 2Δ5/2-A 2Δ5/2, [15.0] 2Δ5/2-X 2Π3/2, and [15.0] 2Π3/2-X 2Π3/2 electronic transitions of NiCl have been observed in the 14 000-16 000 cm−1 region. The [15.0] 2Δ5/2 and [15.0] 2Π3/2 states are identified for the first time. The observed bands have been recorded at high spectral resolution using several techniques, which include intracavity laser spectroscopy (ILS), Fourier transform emission spectroscopy (FTS), and laser induced fluorescence (LIF) spectroscopy. For the ILS absorption spectra, NiCl molecules were produced in a nickel hollow cathode operated with a small amount of CCl4. For the FTS emission spectra, excited NiCl molecules were produced in a King-type carbon tube furnace loaded with NiCl2 and heated to 1600 °C. In the LIF work, NiCl molecules were produced by reacting laser-ablated nickel with PCl3 seeded in argon. Detailed analysis of rotational transition lines indicates that the observed [15.0] 2Δ5/2 and [15.0] 2Π3/2 states are only separated by 10 cm−1 and are interacting with each other. Molecular constants for these newly observed electronic states are reported.