ound ▁has ▁a ▁stretch ing ▁frequency ▁of ▁ 7 7 6   cm − 1 ▁compared ▁to ▁ 9 1 4 . 8   cm − 1 ▁in ▁ne on . ▁The ▁arg on ▁u ran ium ▁dio x ide ▁mole c ule ▁is ▁likely ▁U O 2 Ar 5 . ▁ ▁B ery l li um ▁ox ide ▁When ▁b ery l li um ▁atoms ▁react ▁with ▁o xygen ▁in ▁a ▁solid ▁arg on ▁matrix ▁( or ▁b ery ll ia ▁is ▁ev apor ated ▁into ▁the ▁matrix ) ▁Ar Be O ▁will ▁be ▁formed , ▁and ▁is ▁observable ▁by ▁its ▁inf ra red ▁spectrum . ▁The ▁b ery ll ia ▁mole c ule ▁is ▁strongly ▁polar ised , ▁and ▁the ▁arg on ▁atom ▁is ▁attract ed ▁to ▁the ▁b ery l li um ▁atom . ▁The ▁bond ▁strength ▁of ▁Ar − Be ▁is ▁calculated ▁to ▁be ▁ 6 . 7   k cal / m ol ▁( 2 8   k J / m ol ). ▁The ▁Ar − Be ▁bond ▁length ▁is ▁predicted ▁to ▁be ▁ 2 . 0 4 2   Å . ▁ ▁The ▁cy clic ▁Be 2 O 2 ▁mole c ule ▁can ▁bind ▁two ▁arg on ▁atoms , ▁or ▁one ▁arg on ▁along ▁with ▁another ▁noble ▁gas ▁atom . ▁ ▁Anal og ously , ▁b ery l li um ▁react ing ▁with ▁hydro gen ▁sul f ide ▁and ▁tra pped ▁in ▁an ▁arg on ▁matrix ▁at ▁ 4   K ▁forms ▁Ar Be S . ▁It