In monocrystals of BaO

SrO and

CaO

data from electrical and optical conductivities

photdemission and absorption spectra are so diverse that an accurate energy diagram can not be depicted. This implies that the surface phenomena are more important than the bulk ones. The internal and external work functions obtained from BaO monocrystal film on Ir（lOO）

being single valued

are not consistent with the wide distribution of work functions of tricarbonate cathodes measured by scanning low energy electron probe

indicating that the semiconductor model is not a correct description of commercial oxide cathode. AES measurements show that

the coatings are rich in oxygen

which negates that the oxygen vacancy acts as electron donor. But the fact that the excess bariums are responsible for electron emission may be reconciled with the deficiency of alkaline earth metals during life by the dynamical surface emission center model. This model suggests that an aggregate of atoms with excess barium absorbed on alkaline earth oxides can emit electrons efficiently

which can explain many phenomena observed by modern surface analysis techniques.