Autoionising states of K+and K excited by slow K+impact on He

Autoionisation of potassium ions, K + , and potassium atoms, K, are studied by means of ejected electron spectroscopy. Low-lying doubly excited states of K + and K are identified. The core excited K + 3s3p 6 4s 1 S e , K + 3s3p 6 3d 1 D e and K + 3s3p 6 4p 1 P 0 autoionising states are identified. They are observed at 5.28, 6.59 and 8.01 eV above the K 2+ 3s 2 3p 5 2 P 3 2/ 0 state, respectively. Configuration interaction calculations are carried out on these states. It is suggested that the K + core-excited state are excited through configuration mixing with the K + double excited states.