I have an exam coming up in spectroscopy and well I just can't seem to get it fully or even partially straight in my head for that matter so I'm doing some problems to see if they can help me understand it a bit more and I was wondering if I could get a bit of help and advice on them,

*The fundamental vibrational band of *^{14}N^{16}O exhibits rotational fine structure. The fine structure consists of equally spaced peaks separated by 3.41018 cm^{-1}. Using this datum, calculate the equilibrium internuclear distance in ^{14}N^{16}O.

Assuming that the internuclear distance is unaffected by isotopic enrichment, calculate the rotational constant B for ^{14}N^{18}O.

To calculate the internuclear distance I would us the formula

Only I don't have

*B*, so to get it I would use

And to that I would have to calculate the moment of inertia,

*I*, using

*I = M*_{1}R_{1}^{2} + M_{2}R_{2}^{2}But I don't know what to use as the

*R* values, the distance each atom is from the centre of mass.

Should I be doing something different or using the value 3.41018cm

^{-1} which separate the peaks as outlined in the questions.

Apologies for the length, any help is greatly appreciated.

Adam

P.S. I don't know if I should have posted this here or in the Undergraduate Sub-Forum, apologies if it's in the wrong one.