The elusive 2s3s S-1 level in BII
It has been known for nearly 30 years that the theoretical and experimental values for the energy of the 2s3s S-1 level in singly ionized boron, B it, differ strongly. Since there is much better agreement for other B II levels, it has been concluded that the experimental value for 2s3s S-1 must be revised. Despite a number of recordings over the years of sliding-spark, hollow cathode and beam-foil