Explain in general terms what happens to a molecule when it absorbs a photon: (i) in the UV-visible region of the electromagnetic spectrum; (ii) in the microwave region of the electromagnetic spectrum

(i) In general, when a molecule absorbs a UV-visible photon, an electron is promoted from one of the occupied molecular orbitals to an unoccupied molecular orbital at higher energy.

(ii) In general, when a molecule absorbs a microwave photon, it is promoted from one rotational energy level to the next rotational level at higher energy; for example, from J = 0 to J = 1.