$3.$ Using group theoretical methods, assign the symmetries $($irreps$)$ of the

normal modes of vibration. Identify which modes are IR$-$active and

which are Raman$-$active.

Note: For linear molecules you will have to use a slightly different

method as the reduction formula cannot be used for h $=\backslash$infty $.$

$4.$ From the spectrum you have been provided and your analysis in Q$3,$

identify whether all the optically$-$active vibrations have been observed. If

extra irreps are present specify what are the symmetries

$C_2{H}_2$ Vibrational Spectra

$N{O}_2$ Vibrational Spectra