A theoretical study of negative ions

The role of negative ions in accelerator mass spectrometry (AMS) is reviewe d with a discussion regarding the measurement of electron affinity and isob ar separation. As a prelude for the discussion, a theoretical study concern ing the structure of negative ions, in which the conventional Hund rule for the distribution of electrons in negative ions is violated more or less, i s carried out to calculate the electron affinity from a microscopic point o f view.