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Proton emission (also known as proton radioactivity) is a type of radioactive decay in which a proton is ejected from the nucleus. Proton emission can occur from high-lying excited states in a nucleus following a beta decay, in which case the process is known as beta-delayed proton emission, or can occur from the ground state (or a low-lying isomer) of very proton-rich nuclei, in which case the process is very similar to alpha decay. For a proton to escape a nucleus, the proton separation energy must be negative - the proton is therefore unbound, and tunnels through the Coulomb barrier in a finite time. Proton emission is not seen in naturally-occurring isotopes; proton emitters can be produced via nuclear reactions, usually utilising some kind of particle accelerator.

Although prompt (i.e. not beta-delayed) proton emission was observed from an isomer in Cobalt-53 as early as 1969, no other proton-emitting states were found until 1981, when the proton radioactive ground states of Lutetium-151 and Thulium-147 were observed at experiments at GSI. Research in the field flourished after this breakthrough, and to date more than 25 isotopes have been found to exhibit proton emission. The study of proton emission has aided the understanding of nuclear deformation, masses and structure, and is a wonderfully pure example of quantum tunneling.

In 20022002 is a common year starting on Tuesday (see link for calendar). 2002 was the first palindromic year since 1991 and the last until 2112. 2002 was also designated: International Year of Ecotourism and Mountains National Science Year in the United Kingdom, the simultaneous emission of two protons was observed from the nucleus Iron-45This article is about metallic iron. For the ironing device, see ironing manganese iron cobalt Fe Ru Full table General Name, Symbol, Number iron, Fe, 26 Chemical series transition metal Group, Period, Block 8 (VIIIB), 4 , d Density, Hardness 7874 kg/m3, in experiments at GSI and GANIL (Grand Accelerateur National d'Ions Lourds, near CaenCaen Region Basse-Normandie Departement Calvados Arrondissement24 cantons287 communes389,973 habitants Cantonschief town of 9 cantons(13 common, 162,707 habitants) HabitantsCaennais Population (1999)117,157 habitants Intercommunality ( 2004) Agglomeration).