Phys1070: intro physics for life sci - lecture 18: light absorption by biological. In the lowest energy state of the atoms molecule the pi electron energy levels are filled up to n=4 for octene. This means that the first empty state is n=5. Excited states = correspond to moving pi electrons to a higher energy level. Therefore n=5 is also the first excited state of this molecule. When an electron jumps up to a higher energy level they absorb light. When they return from a higher energy level to ground state, electrons emit/fluoresce light. The energy to excite the molecule has to come from the light that is absorbed. The first excited state is most likely the energy level to be populated by excited electrons first. Electrons jumping from ground state to more than one energy level higher obviously take more energy. These are called second, third, etc. excited states.
