inst ant ane ously ▁dec ays ▁into ▁two ▁alpha ▁particles . ▁This ▁activity ▁was ▁observed ▁again ▁several ▁months ▁later , ▁and ▁was ▁infer red ▁to ▁origin ate ▁from ▁ 8 Be . ▁ ▁Properties ▁▁ ▁B ery l li um - 8 ▁is ▁un bound ▁with ▁respect ▁to ▁alpha ▁emission ▁by ▁ 9 2 ▁ke V ; ▁it ▁is ▁a ▁reson ance ▁having ▁a ▁width ▁of ▁ 6 ▁e V . ▁The ▁nucle us ▁of ▁hel ium - 4 ▁is ▁particularly ▁stable , ▁having ▁a ▁doub ly ▁magic ▁configuration ▁and ▁larger ▁binding ▁energy ▁per ▁nucle on ▁than ▁ 8 Be . ▁As ▁the ▁total ▁energy ▁of ▁ 8 Be ▁is ▁greater ▁than ▁that ▁of ▁two ▁alpha ▁particles , ▁the ▁decay ▁into ▁two ▁alpha ▁particles ▁is ▁ener get ically ▁favor able , ▁and ▁the ▁synth esis ▁of ▁ 8 Be ▁from ▁two ▁ 4 He ▁nuc lei ▁is ▁end oth erm ic . ▁The ▁decay ▁of ▁ 8 Be ▁is ▁facil itated ▁by ▁the ▁structure ▁of ▁the ▁ 8 Be ▁nucle us ; ▁it ▁is ▁highly ▁de formed , ▁and ▁is ▁believed ▁to ▁be ▁a ▁mole c ule - like ▁cluster ▁of ▁two ▁alpha ▁particles ▁that ▁are ▁very ▁easily ▁separated . ▁Furthermore , ▁while ▁other ▁alpha ▁nu cl ides ▁have ▁similar ▁short - l ived ▁reson ances , ▁ 8 Be ▁is ▁exception ally ▁already ▁in ▁the ▁ground ▁state . ▁The ▁un bound ▁system ▁of ▁two ▁α - part icles ▁has ▁a ▁low ▁energy ▁of ▁the ▁C oul omb ▁bar rier , ▁which ▁enables