Chemical shift of Zeeman masses in polar semiconductors

We discuss the problem of determining effective masses from the Zeeman splitting of 2p-levels in shallow impurities. In polar semiconductors we find the Zeeman mass to depend upon the chemical nature of the impurity (chemical shift), which can usually be described by a central-cell potential. In spite of its short range, it can influence even 2p-levels, if, due to electron-phonon interaction, 1s-one-phonon states are admixed to 2_p-zero-phonon states.