Laser and Fourier transform spectroscopy of ${}^7$Li${}^{88}$Sr

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 $1^2{\mathrm{\Sigma }}^{+}$ and $2^2{\mathrm{\Sigma }}^{+}$ states were studied using laser excitation to facilitate the assignment of the lines. The ground state could be described for $v^{\mathrm{\prime }\mathrm{\prime }}=$ 0 - 2, $N^{\mathrm{\prime }\mathrm{\prime }}$ up to 105 and the $2^2{\mathrm{\Sigma }}^{+}$ state for $v^{\mathrm{\prime }}=0$ up to $N^{\mathrm{\prime }}=68$. For both states, Dunham coefficients, spin-rotation parameters and potential energy curves were evaluated. A coupling of the $2^2{\mathrm{\Sigma }}^{+}$ state to the $1^2\mathrm{\Pi }$ state was observed, allowing a local description with Dunham coefficients of the $1^2\mathrm{\Pi }$ state and an approximate evaluation of the coupling strength.