Rotational analysis and hyperfine structures of A2Π1/2 → X2Σ1/2 transition in 25,26MgF isotope molecules

High resolution ro-vibrational spectroscopy of the A2Π1/2(v′ = 0) → X2Σ1/2(v = 0) band, for the buffer-gas-cooled magnesium monofluoride (25,26MgF) isotope molecules, has been measured by the in-cell direct absorption. Due to the decent populations in the low-lying rotational states (X2Σ1/2(v = 0,  N = 0,  1)) for the cooled 25,26MgF molecules, the rotational levels and constants of the A2Π1/2(v′ = 0) state of 25,26MgF are accurately determined. Furthermore, hyperfine-structure levels of X2Σ1/2(v = 0,  N = 1) of 25,26MgF are successfully measured by the laser induced fluorescence. Such studies complement previous studies on the more abundant 24MgF molecule and are useful for precision measurement and relevant laser cooling experiments.