In homework 2, you were asked to draw a pure vibrational spectra for a diatomic molecule. why do you not ever expect to observe a pure vibrational spectrum? given the selection rules for vibrational excitations by infrared electromagnetic radiation (light) and considering rotational excitations, draw the expected absorption rotational-vibrational (ro-vibrational) spectrum for a heteronuclear diatomic molecule transitioning from the v = 0 to v = 1 energy level. on your drawing, show explicitly the rotational transitions: ∆ = 1, 2, 3, 4 and ∆ = −1, − 2, −3, −4. b) what does the ro-vibrational absorption spectrum look like for a homonuclear diatomic molecule?