and Historical Overview.- F Centers and Rare-Earth Ion Defects in Alkali Halides.- Properties of Molecular Defects.- Theoretical Models for E-V Transfer.- FH(CN?) Centers.- CN? Next to an Anion Vacancy Occupied by No Electron or Two Electrons.- FH(OH?) Centers.- Interaction Between F Electrons and Distant OH? Molecules.- Ytterbium Ions and CN? Molecules.- Europium and CN? Molecules.- Samarium and CN? Molecules.- Other Defect Complexes.- Summary. and Historical Overview.- F Centers and Rare-Earth Ion Defects in Alkali Halides.- Properties of Molecular Defects.- Theoretical Models for E-V Transfer.- FH(CN?) Centers.- CN? Next to an Anion Vacancy Occupied by No Electron or Two Electrons.- FH(OH?) Centers.- Interaction Between F Electrons and Distant OH? Molecules.- Ytterbium Ions and CN? Molecules.- Europium and CN? Molecules.- Samarium and CN? Molecules.- Other Defect Complexes.- Summary.