Rotational and hyperfine structure in the yellow system of CuF

Previous spectroscopic studies of copper monofluoride have suggested that the excited electronic state involved in the yellow system is either ³Σ^? or a (¹Π, ¹Σ) “p-complex”. A Doppler-limited (HWHM ? 0.4 GHz), laser-induced fluorescence study of the (0, 0) band of the ⁶³Cu¹⁹F isotopic species was performed in order to make a more definite assignment of the upper state. As a result of increased resolution, many of the rotational lines appear as partially resolved quartets resulting from the ⁶³Cu ($\text{I =}\text{3}\text{2}$) nuclear hyperfine splitting. It was not possible on the evidence available to decide between the alternative assignments for the upper state. Assuming a ³Σ^? state, 200 features were assigned, measured, and fitted by a least-squares procedure to determine values for the parameters (cm^?1) of CuF in the excited state: T₀ = 17 574.9663(12), λ₀ = ? 27.7149(11), λ_D0 = 0.001161(1), B₀ = 0.375035(2), 10⁶D₀ = 0.510(1), γ₀ = 0.01074(6), $\text{b}{}_{\mathrm{F}}\text{(}{}^{63}\text{Cu}\text{) = 0.032(2)}$, $\text{c(}{}^{63}\text{Cu}\text{) = ?0.039(7)}$. The ⁶³Cu hyperfine parameters are interpreted in terms of possible electronic models of CuF in the A state.