“…The DES correlation types can be abbreviated by letters [8]: for the 1 S e and 1 D e states converging to the N ¼ 2 threshold, that are in the focus of this work, na is equivalent to nð1; 0Þ þ , whereas nb stands for nð−1; 0Þ þ and nð0; 1Þ 0 quantum numbers of states associated with the 1 S e and 1 D e symmetry, respectively. In the last decade, the fluorescence decay channel [29], with branching to the 1s2s metastable states [30], was proven a sensitive tool for studying DES with high resolution synchrotron sources in the field-free [31][32][33][34], and static electric [20,35,36] and magnetic [37] field environment.…”