Excitation of the Ca atom from the metastable states by electron impact

Electron impact excitation of the Ca atoms from the metastable states has been studied by an optical method in crossed atomic and electron beams in the energy range from threshold up to 30 eV. The relative excitation functions and the absolute values of the emission cross sections for 16 spectral transitions excited both from the metastable and ground states have been obtained. The experimental results are compared with the close-coupling and Born - Ochkur calculations carried out with the extensive many-configuration target wavefunctions. In most cases the theoretical excitation functions agree within the limits of experimental error (50%) with the experimental results including the resonance-like structure in the near-threshold region allowing us to classify uniquely the resonances observed.