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. They took chains of carbon atoms, polyenes, and calculated how electrons inside them move when light is absorbed. Then they added random kicks to mimic the environment and watched how the electron motion gets disrupted and the absorption color changes.
With computer animations and MATLAB code, students can 'play' with parameters themselves and see how the spectrum changes. This turns abstract theory into a hands-on experience: the molecule is no longer a point but a living system interacting with its surroundings.
In solution, molecules collide roughly every $10^{-13}$ seconds — faster than one oscillation of light lasts.