The phrase "excited molecule" refers to a molecule that has absorbed energy and become more energetic than its usual state. It is like a molecule that is really happy and active because it has gained extra energy. Full definition
But typically, only one excited molecule in four emits light: the other three give off their energy as heat. (sciencemag.org)
Energy is freely transferred into the plasmons from excited molecules incorporated into the devices, which get their energy from a typical large - scale titanium sapphire laser. (discovermagazine.com)
``... this pulls the carbon in one direction and the oxygens in another, so an electromagnetic wave that vibrates at the correct frequency can excite the molecule into a vibrational motion in which the carbon atom moves in the opposite direction to the two oxygen atoms. (realclimate.org)