Can anyone help with interpretation of this energy level diagram for Lithium-6 I found on internet--it is from the Duke University department of Physics. http://www.tunl.duke.edu/nucldata/figures/06figs/06_03_2002.pdf I am not sure I understand the equation for the 13.3 MeV energy level predicted--what exactly does it mean to have a minus (-) alpha ? Does this mean the energy of the alpha (~28.2957 MeV) is to be subtracted from the other members ? Is this alpha a type of negative energy potential, perhaps from antimatter ? Thanks for any help.