- d fe pe ) Cr ( CO ) 3 Ar . ▁ ▁Other ▁noble ▁gas ▁complex es ▁have ▁been ▁studied ▁by ▁phot ol ysis ▁of ▁car b ony ls ▁dissol ved ▁in ▁liquid ▁rare ▁gas , ▁possibly ▁under ▁pressure . ▁These ▁Kr ▁or ▁X e ▁complex es ▁decay ▁on ▁the ▁time ▁scale ▁of ▁seconds , ▁but ▁arg on ▁does ▁not ▁seem ▁to ▁have ▁been ▁studied ▁this ▁way . ▁The ▁advantage ▁of ▁liquid ▁noble ▁g ases ▁is ▁that ▁the ▁medium ▁is ▁completely ▁transparent ▁to ▁inf ra red ▁radiation , ▁which ▁is ▁needed ▁to ▁study ▁the ▁bond ▁v ibration ▁in ▁the ▁sol ute . ▁ ▁Att empt s ▁have ▁been ▁made ▁to ▁study ▁cab ony l – arg on ▁ad duct s ▁in ▁the ▁gas ▁phase , ▁but ▁the ▁interaction ▁appears ▁to ▁be ▁too ▁weak ▁to ▁observe ▁a ▁spectrum . ▁In ▁the ▁gas ▁form , ▁the ▁absor ption ▁lines ▁are ▁bro aden ed ▁into ▁bands ▁because ▁of ▁rotation ▁that ▁happens ▁freely ▁in ▁a ▁gas . ▁The ▁arg on ▁ad duct s ▁in ▁liqu ids ▁or ▁g ases ▁are ▁un stable ▁as ▁the ▁mole cules ▁easily ▁react ▁with ▁the ▁other ▁phot ol ysis ▁products , ▁or ▁dim er ize , ▁elimin ating ▁arg on . ▁ ▁Co in age ▁metal ▁mon oh al ides ▁The ▁arg on ▁coin age ▁metal ▁mon oh al ides ▁were ▁the ▁first ▁noble ▁gas ▁metal ▁hal ides ▁discovered , ▁when ▁the ▁metal ▁mon oh al ide ▁mole cules ▁were ▁put ▁through ▁an ▁arg on ▁jet . ▁There ▁were ▁first ▁found