The strongly localized one-electron (D-0) and two-electron (D-) donor
states are considered with the lattice deformation around tile donor c
enter taken into account. For GaAs, the donor energy levels have been
calculated as functions of the hydrostatic pressure. Tile calculated e
nergy positions and pressure coefficients agree with the experimental
data. It is shown that the interaction with phonons reduces the probab
ility of radiative transitions between tile states of different locali
zation and leads to the metastability of shallow-level donor states wi
th respect to the D- state in GaAs and both the states (D-0 and D-) in
CdF2.