The Magnesium Isotopologues of MgH in the A(2)Pi-X-2 Sigma(+) System

Abstract

Using laboratory hollow cathode spectra we have identified lines of the less common magnesium isotopologues of MgH, (MgH)-Mg-25 and (MgH)-Mg-26, in the A(2)Pi-X-2 Sigma(+) system. Based on the previous analysis of (MgH)-Mg-24, molecular lines have been measured and molecular constants derived for (MgH)-Mg-25 and (MgH)-Mg-26. Term values and linelists, in both wavenumber and wavelength units, are presented. The A(2)Pi-X-2 Sigma(+) system of MgH is important for measuring the magnesium isotope ratios in stars. Examples of analysis using the new linelists to derive the Mg isotope ratio in a metal poor dwarf and giant are shown.