An alternative representation of multichannel Rydberg spectra: beyond the Lu-Fano plot, with an application to manganese

The Lu-Fano plot is a well-known graphical representation developed for multichannel Rydberg spectroscopy and has found its use in quantum defect theory. The present study develops a modification of the traditional Lu-Fano plot which is particularly useful in situations with more than two ionization thresholds or where one is exploring the bound states lying very far below closely split thresholds. An example application to Rydberg series of the manganese atom illustrates its use in a practical problem.