Rotational analysis and hyperfine structures of A²Π_1/2 → X²Σ_1/2 transition in ^25,26MgF isotope molecules

High resolution ro-vibrational spectroscopy of the A²Π_1/2(v′ = 0) → X²Σ_1/2(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 (X²Σ_1/2(v = 0, N = 0, 1)) for the cooled ^25,26MgF molecules, the rotational levels and constants of the A²Π_1/2(v′ = 0) state of ^25,26MgF are accurately determined. Furthermore, hyperfine-structure levels of X²Σ_1/2(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.