Electronic transitions of iridium monoxide: ground and low-lying electronic states

The electronic transition spectrum of IrO in the spectral region between 448 and 650 nm has been recorded and analyzed using laser vaporization/reaction free jet expansion and laser induced fluorescence spectroscopy. The IrO molecule was produced by reacting laser-ablated iridium atoms with N(2)O seeded in argon. Five electronic transition systems, namely, the [17.6]2.5 - X(2)Δ(5/2), [17.8]2.5 - X(2)Δ(5/2), [21.5]2.5 - X(2)Δ(5/2), [22.0]2.5 - X(2)Δ(5/2), and [21.9]3.5 - Ω = 3.5 systems were identified. Transition lines of both the (191)IrO and (193)IrO isotopes were observed and analyzed. IrO was determined to have a X(2)Δ(5/2) ground state. A least squares fit of the measured rotational lines yielded molecular constants for the ground and low-lying electronic states. A molecular orbital energy level diagram has been used to help with the assignment of the observed electronic states.