Question

which of the following molecules exhibit rotational and or vibrational spectra h2 , hf, co, no

Answer 1

Hf exhibit rotational or vibrational spectra because other are linear molecules.

Answer 2

CO for instance shows only rotational spectra whereas $H_2$ shows only vibrational spectra.  

Explanation:

Hf shows rotational and or vibrational spectra. This is because unlike the molecules of $H_2$, CO and NO; Hf is not a linear molecule.

The rotational spectra correspond to energy of microwave radiations. Vibrational energies correspond to infrared radiations. Hf is a diatomic molecule in which rotational as well as vibrational energy levels can be seen in a combined form.

CO, NO, and $H_2$ exhibit either rotational spectra or vibrational spectra but not both. CO for instance shows only rotational spectra whereas $H_2$ shows only vibrational spectra.