Question

The diatomic molecule boron nitride, 11B14N was studied by the spectroscopist Gerhard Herzberg in
1940. It was produced via a discharge involving boron trichloride and dinitrogen in the presence of
helium.

a) Given that the fundamental transition occurs at 1490.0 cm-1 and the first overtone at 2955.4
cm-1, determine the harmonic wavenumber and the anharmonicity.

b) Given that the centrifugal distortion constant is 8.1 x 10-6 cm-1, determine the rotational
constant of

the molecule. State any approximations made. Ignore rotational-vibrational coupling.

c) Determine the bond length of the molecule in Å. Atomic masses of 11B and 14N are 11:009 µ and
14:003 µ respectively.

Answer 1