The diagrams are named after Walter Grotrian, who introduced them in his 1928 paper Graphische Darstellung der Spektren von Atomen und Molekülen mit 1, 2 und 3 Valenzelektronen (Graphical representation of the spectra of atoms and molecules with 1, 2 and 3 valence electrons).
The Grotrian diagram in atomic spectroscopy showing the allowed transitions between atomic energy levels
Walter Scott | Sir Walter Scott | Walter Cronkite | Walter Raleigh | Walter Benjamin | Walter Mondale | Walter Matthau | Walter Gropius | Walter Hamma | Walter Savage Landor | Walter Burley Griffin | Walter Payton | Walter | Bruno Walter | Walter Winchell | Walter Crane | Walter Rilla | Walter Koenig | Walter Brennan | Walter Sickert | Walter Pidgeon | Walter Isaacson | Walter Damrosch | Walter Crickmer | Walter Brueggemann | Walter Reed | Walter Browne | Little Walter | Walter Runciman, 1st Viscount Runciman of Doxford | Walter Rothschild, 2nd Baron Rothschild |
It was not until the 1930s that Walter Grotrian and Bengt Edlén discovered that the spectral line at 530.3 nm was due to highly ionized iron (Fe13+); other unusual lines in the coronal spectrum were also caused by highly-charged ions, such as nickel, the high ionization being due to the extreme temperature of the solar corona.