▁The ▁X - ray ▁excited ▁arg on ▁atoms ▁are ▁in ▁the ▁ 4 p ▁state . ▁ ▁Arg on ▁mon oh yd ride ▁is ▁un stable ▁in ▁its ▁ground ▁state , ▁ 4 s , ▁as ▁a ▁neutral ▁in ert ▁gas ▁atom ▁and ▁a ▁hydro gen ▁atom ▁rep el ▁each ▁other ▁at ▁normal ▁inter m ole cular ▁distances . ▁When ▁a ▁higher - energy - level ▁Ar H * ▁em its ▁a ▁phot on ▁and ▁reaches ▁the ▁ground ▁state , ▁the ▁atoms ▁are ▁too ▁close ▁to ▁each ▁other , ▁and ▁they ▁rep el ▁and ▁break ▁up . ▁However ▁a ▁van ▁der ▁Wa als ▁mole c ule ▁can ▁exist ▁with ▁a ▁long ▁bond . ▁However , ▁excited ▁Ar H * ▁can ▁form ▁stable ▁R yd berg ▁mole cules , ▁also ▁known ▁as ▁exc im ers . ▁These ▁R yd berg ▁mole cules ▁can ▁be ▁considered ▁as ▁a ▁pro ton ated ▁arg on ▁core , ▁surrounded ▁by ▁an ▁electron ▁in ▁one ▁of ▁many ▁possible ▁higher ▁energy ▁states . ▁ ▁Form ation : ▁Ar ▁+ ▁ ν ▁→ ▁Ar * ; ▁Ar * ▁+ ▁H 2 ▁→ ▁Ar H * ▁+ ▁H ▁ ▁Instead ▁of ▁di h ydro gen , ▁other ▁hydro gen ▁containing ▁mole cules ▁can ▁also ▁have ▁a ▁hydro gen ▁atom ▁abstract ed ▁by ▁excited ▁arg on , ▁but ▁note ▁that ▁some ▁mole cules ▁bind ▁hydro gen ▁too ▁strongly ▁for ▁the ▁reaction ▁to ▁proceed . ▁For ▁example , ▁ac et yl ene ▁will ▁not ▁form ▁Ar H ▁this ▁way . ▁ ▁In ▁the ▁van