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

Abstract

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