# Atomic Spectra

A molecule with angular momentum L and moment of inertia I has a rotational energy $$E = L^2 / 2I$$. Since angular momentum is quantized, find the wavelength of the photons emitted in n=2 to n=1 transition of the H2 molecule. This molecule has a moment of inertia $$I = [tex]0.5mr^2$$, where m = 938Mev/c^2 and r = 0.074nm.

My attempt is to say $$L = [[l(l+1)]^.5}\hbar$$ and use l =2 for n=2 state and l = 1 for n=1. Put these values for L into the equation for E.
Then E2 - E1 = $$\triangle E.$$

$$\triangle E = hf, v = \lambda f.$$

=> $$\lambda = hv / \triangle E = hc / \triangle E$$

I've no idea if I'm on the right track, couldn't find anything similar in the textbook.

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