The energy levels of positronium in eV are given by: En = - 6.8/n2 From this the positronium spectrum must contain some frequencies smaller than those of gamma rays including some lines in the visible spectrum. My problem is that I have been trying to find photographs and other details of the positronium spectrum but have found nothing. Positronium has been known of for a long time so my guess is that there are problems in displaying the spectrum. Either that or I have been searching in the wrong places. Can anyone enlighten me please? Thank you.