8 . 7   cm − 1 ▁when ▁arg on ▁attach es ▁to ▁the ▁nick el ▁atom . ▁ ▁Other ▁ ions ▁Some ▁other ▁binary ▁ ions ▁observed ▁that ▁contain ▁arg on ▁include ▁Ba Ar 2 + ▁and ▁, ▁V Ar + , ▁Cr Ar + , ▁Fe Ar + , ▁Co Ar + , ▁and ▁Ni Ar + . ▁ ▁Gold ▁and ▁silver ▁cluster ▁ ions ▁can ▁bind ▁arg on . ▁Kn own ▁ ions ▁are ▁, ▁, ▁, ▁ ▁and ▁. ▁These ▁have ▁a ▁tri angular ▁sh aped ▁met all ic ▁core ▁with ▁arg on ▁bound ▁at ▁the ▁vertex es . ▁ ▁Ar F + ▁is ▁also ▁known ▁to ▁be ▁formed ▁in ▁the ▁reaction ▁ ▁+ ▁Ar ▁→ ▁Ar F + ▁+ ▁F ▁and ▁also ▁Ar + ▁+ ▁F 2 ▁→ ▁Ar F + ▁+ ▁F . ▁and ▁also ▁SF ▁+ ▁Ar ▁→ ▁Ar F + ▁+ ▁SF . ▁The ▁ ions ▁can ▁be ▁produced ▁by ▁ult rav io let ▁light ▁at ▁ 7 9 . 1   nm ▁or ▁less . ▁The ▁ion isation ▁energy ▁of ▁flu or ine ▁is ▁higher ▁than ▁that ▁of ▁arg on , ▁so ▁break up ▁occurs ▁thus : ▁Ar F + ▁→ ▁Ar + ▁+ ▁F . ▁The ▁millimeter ▁wave ▁spectrum ▁of ▁Ar F + ▁between ▁ 1 1 9 . 0 2 3 2 ▁and ▁ 5 0 5 . 3 1 5 5   G Hz ▁has ▁been ▁measured ▁to ▁calculate ▁mole cular ▁constants ▁B 0   =   , ▁D 0  