High resolution spectroscopy of the low-lying states of strontium bromide, ytterbium fluoride, ytterbium chloride and ytterbium bromide radicals

High resolution laser excitation spectra of the 2–1, 3–2 and 4–3 bands of the A2Π ← X2Σ+ system of 88Sr 79Br and 88Sr81Br have been recorded. Observed perturbations in the υ_A = 3 and 4 levels of the A2Π_1/2 sub-state are confirmed to be caused by level crossings with the υ _B = 0 and 1 levels of the B2Σ + state. A least squares fit of all known electronic data of both the A2Π ← X 2Σ+ and B2Σ + ← X2Σ+ systems was employed to simultaneously characterize the υ _A = υ_B + 3 level crossings, as well as the 2Π ∼ 2Σ+ interactions, responsible for Λ-doubling in the 2Π state and “spin-rotation” splitting in the 2Σ + state. An unobserved level crossing is predicted to occur between levels of e parity of υ_B = 2 and υ_A = 5.; The pure rotational spectra of low-lying υ = 0 and 1 vibrational levels of the 2Σ+ ground states of several isotopomers of YbF, YbCl and YbBr were recorded using a pulsed jet cavity Fourier transform microwave spectrometer. Through least squares fits, parameters describing rotational, fine and hyperfine effects (such as Fermi-contact, dipole-dipole coupling and nuclear spin-rotation coupling) are presented.; The υ = 0 and 1 vibrational levels of the B 2Σ+ state of YbBr were characterized for the first time through a high resolution laser investigation of rotational transitions in several bands of the B2Σ+ ← X2Σ+ system. The spectra were found to be highly congested, owing to the multitude of isotopomers with similar rotational B_υ values, which made assignment of rotational structure difficult. The effects of electronic field shifts were observed as small differences between calculated and observed isotope shifts of 174YbBr and 172YbBr isotopomers. This field shift has been observed in only a few heavy molecules, and its effect on electronic, vibrational and rotational parameters is discussed.; Finally, an absorption study of the A2Π ← X2Σ+ system of YbBr has been made at high resolution using a laser arrangement. Similar to the B − X study, spectra of the A − X system were observed to be highly congested, making analysis challenging. Besides highly accurate estimates of the A state equilibrium bond length, comparisons with the analogous YbF and YbCl molecules are discussed.