Mass polarisation of H- and He in a strong magnetic field

Mass polarisation corrections are computed to the first order of perturbation, for the lowest ML = 0 to -2 bound states of H- and He in a strong magnetic field (B ≥ 1 MT). The zero-order energies and wave functions are provided by a previous variational calculation. The mass polarisation corrections split into two components, respectively longitudinal and transverse to the field. Like the field-free mass polarisation, the longitudinal component remains weak for all the states studied. However, the -1s-, -1T- and -2s+ transverse mass polarisation corrections become significant with respect to the binding energy when the magnetic field is sufficiently high. (author)