MCHF calculations of isotope shifts and oscillator strengths for transitions between low-lying states in Be-like systems and neutral magnesium

Results from systematic multiconfiguration Hartree-Fock calculations of isotope shifts and oscillator strengths are reported for the and transitions in the Be isoelectronic sequence ( Z = 4-10). In addition values for the same properties as well as for the hyperfine interaction constants are presented for the - transitions in Mg I. Different models for electron correlation are used, and it is shown that valence and core-valence effects alone are not sufficient to obtain accurate values for the isotope shifts, but that also core-core effects need to be accounted for.