The moment of inertia for an axis perpendicular to the C3 symmetry axis of NH3 is Iperp = 2.82 1047 kg m2 . The C3 symmetry axis goes through the N nucleus. What type of top is NH3? What is the separation between a pair of neighbouring lines in the rotational spectrum. You will need to calculate the moment of inertia for the axis parallel to the C3 symmetry axis and it is 2mHr 2 (1 cos ). is the the bond angle which is 106.8 . r is the bond length which is 1.014 1010m