ok but weird question are any of you like structural engineers that understand vibration and damping really well? It turns out this is super important in organic pigments and fluorophores, they’re these kind of stiff kind of floppy things that start jiggling once they absorb light…
I tend to think within the “classical nuclei, quantum electron” picture at absolute zero.
So there’s an organic molecule with the ground state electron wavefunction, and nuclei are point particles with 0 momentum, positioned to minimize ground state energy. Then it absorbs light, and now it’s in an excited state. But the geometry isn’t the minimum energy geometry for the excited state, so now there’s feynman-hellman forces on the nuclei. So they move to the geometry that minimizes the excited state, but when they get there, they have momentum. And now the molecule is vibrating, the nuclei oscillate around the minimum-energy geometry. And eventually it emits light, and there’s some randomness in the emission frequency depending on where it is in that oscillation when it happens. So we get some spectral broadening, and some energy lost as heat
(via sun-lit-goth)







