Why Molecules Don't Sing Just One Note
Strike a tuning fork, and it rings with a single pure note. But if the fork is trembling and people are chattering nearby, the sound won't be perfect. Same with molecules: each one absorbs light of a specific color, but due to its own vibrations and the jostling of neighbors, that color gets smeared out.
The authors of the paper figured out how to show this to students without complex formulas.