▁much ▁longer ▁time ▁than ▁many ▁other ▁similar ▁pro ton ated ▁c ations . ▁ ▁Ar H + ▁+ ▁e − ▁→ ▁Ar H * ▁→ ▁Ar ▁+ ▁H ▁ ▁Art ific ial ▁Ar H + ▁made ▁from ▁earth ly ▁Ar ▁contains ▁mostly ▁the ▁is ot ope ▁ 4 0 Ar ▁rather ▁than ▁the ▁cosm ically ▁abund ant ▁ 3 6 Ar . ▁Art ific ial ly ▁it ▁is ▁made ▁by ▁an ▁electric ▁dis charge ▁through ▁an ▁arg on - h ydro gen ▁mixture . ▁ ▁Natural ▁occurrence ▁In ▁the ▁C rab ▁Neb ula , ▁Ar H + ▁occurs ▁in ▁several ▁sp ots ▁revealed ▁by ▁emission ▁lines . ▁The ▁strong est ▁place ▁is ▁in ▁the ▁Southern ▁Fil ament . ▁This ▁is ▁also ▁the ▁place ▁with ▁the ▁strong est ▁concentration ▁of ▁Ar + ▁and ▁Ar 2 + ▁ ions . ▁The ▁column ▁density ▁of ▁Ar H + ▁in ▁the ▁C rab ▁Neb ula ▁is ▁between ▁ 1 0 1 2 ▁and ▁ 1 0 1 3 ▁atoms ▁per ▁square ▁cent imeter . ▁Poss ibly ▁the ▁energy ▁required ▁to ▁ex cite ▁the ▁ ions ▁so ▁that ▁then ▁can ▁emit , ▁comes ▁from ▁coll isions ▁with ▁electrons ▁or ▁hydro gen ▁mole cules . ▁Tow ards ▁the ▁Mil ky ▁Way ▁centre ▁the ▁column ▁density ▁of ▁Ar H + ▁is ▁around ▁. ▁ ▁Cl uster ▁arg on ▁c ations ▁The ▁di arg on ▁c ation , ▁ ▁has ▁a ▁binding ▁energy ▁of ▁ 1 . 2 9   e V . ▁ ▁The ▁tri arg on ▁c ation ▁