Spectroscopic Support for Frontier Orbital Interactions

I2 vapor is purple or violet, absorbing near 520 nm, with no charge-transfer bands. 

Ij in benzene is red violet, absorbing near 500 nm, with a charge-transfer band at about 300 nm. 

Ij in aqueous Kl is brown, absorbing near 360 nm, with charge-transfer bands at higher energy. 

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