Optical–optical double resonance spectroscopy of YBr and YCl

High resolution optical–optical double resonance (OODR) spectra of YBr and YCl in the spectral region between 338.9 and 371.7 nm have been recorded and analysis. For YBr, the v = 4–6 levels of the J 1 Π state and the v = 1–3 levels of the K 1 Π state were observed via the intermediate C 1Σ state from the X 1Σ state. For YCl, the v = 0–2 levels of the I 1Δ state was reached via the intermediate B 1 Π state from the X 1Σ+ state. Rotational and vibrational constants for these electronic states were determined.