8 , ▁ 4 5 ▁and ▁ 5 4 , ▁and ▁ 7 0 ▁arg on ▁atoms , ▁which ▁are ▁numbers ▁for ▁ icos ah ed ral ▁shapes . ▁ ▁By ▁z apping ▁co pper ▁metal ▁with ▁a ▁U V ▁las er ▁in ▁an ▁arg on - car bon ▁mon ox ide ▁mixture , ▁arg on ▁tag ged ▁co pper ▁car b ony l ▁c ations ▁are ▁formed . ▁These ▁ ions ▁can ▁be ▁studied ▁by ▁obser ving ▁which ▁w avel ength s ▁of ▁inf ra red ▁radiation ▁cause ▁the ▁mole cules ▁to ▁break ▁up . ▁These ▁mole cular ▁ ions ▁include ▁Cu CO + Ar , ▁Cu ( CO ) 2 + Ar , ▁Cu ( CO ) 3 + Ar , ▁Cu ( CO ) 4 + Ar ▁which ▁are ▁respectively ▁dis rupted ▁to ▁lose ▁arg on , ▁by ▁inf ra red ▁w aven um bers ▁ 2 2 1 6 , ▁ 2 2 2 1 , ▁ 2 2 0 5 ▁and ▁ 2 1 9 4   cm − 1 ▁respectively . ▁The ▁arg on ▁binding ▁energy ▁is ▁respectively ▁ 1 6 . 3 , ▁ 1 . 0 1 , ▁ 0 . 9 7 ▁and ▁ 0 . 2 3 ▁k cal / m ol . ▁The ▁inf ra red ▁absor ption ▁peak ▁for ▁Cu ( CO ) 3 + Ar ▁is ▁ 2 2 0 5   cm − 1 ▁compared ▁to ▁ 2 1 9 9   cm − 1 ▁for ▁Cu ( CO