/aa8ca0. ----------------------LiSr was produced in a heat-pipe oven and its thermal emission spectrum around 9300 cm −1 was recorded by a high resolution Fourier transform spectrometer. In addition, selected lines of the spectrum of deeply bound vibrational levels of the 1 2 Σ + and 2 2 Σ + states were studied using laser excitation to facilitate the assignment of the lines. The ground state could be described for v ′′ = 0 to 2, N ′′ up to 105 and the 2 2 Σ + state for v ′ = 0 up to N ′ = 68. For both states, Dunham coefficients, spin-rotation parameters and potential energy curves were evaluated. A coupling of the 2 2 Σ + state to the 1 2 Π state was observed, allowing a local description with Dunham coefficients of the 1 2 Π state and an approximate evaluation of the coupling strength.

KCa was produced in a heatpipe oven and its thermal emission spectrum around 8900 cm −1 was recorded by a high resolution Fourier transform spectrometer. In addition, many selected transitions of this spectrum between deeply bound vibrational levels of the X(1) 2 Σ + and (2) 2 Σ + states were studied using laser excitation to facilitate the assignment of the lines. The ground state is described for v ′′ = 0 -5 and the (2) 2 Σ + state for v ′ = 0 -8 with rotational levels up to 175. For both states, Dunham coefficients, spin-rotation parameters and potential energy curves are derived.

We analyse rovibrational transitions of the (2)2Σ+–X(1)2Σ+ system of LiSr and find the energy levels of the (2)2Σ+ state to be perturbed by coupling between the (2)2Σ+ and (1)2Π states. We present an analysis of the coupled system yielding molecular parameters for the lowest vibrational levels of the (2)2Σ+ state and for higher vibrational levels of the (1)2Π state together with molecular coupling constants. Improved Dunham coefficients for the rovibrational levels of the X(1)2Σ+ state are also obtained, where the correlation with the parameters of the excited states is removed completely.

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