ENERGY LEVELS OF SINGLY-IONIZED AMERICIUM - 241Am II

The lowest pair of Am II levels 5f77s 9S4 , 7S3 was reported by Fred and Tomkins in (54.1) and the analysis started with the search for line pairs having constant differences in wavenumbers, isotope shift and hyperfine structure. A few even J = 2 and J = 5 levels were found from the hyperfine structure analysis of their unique strong transition to 5f7(8S)7s . A total of 173 Am II lines are classified in (57.1), and 74 of these lines involve three levels of 5f76d. According to the predicted energy of the 5f76d 9D2 level (71.2), these three levels are respectively either 9D2 , 9D3 and 9D4 , or 9D3 , 9D4, and 9D5 . None of these two possibilities is compatible with all J-values of the even levels. The needed revision of Am II is planned, by using the same data as for Am I (unp.25). Due to the breakdown of LS coupling and to configuration mixing, the even levels of Am II could not be labelled by analogy with Eu II.