Estimating the energy required for dissociation from visible absorption spectra

I have been having trouble solving the following problem. The question calls for an estimation of the energy (in kj/mol) required to dissociate ClO in its excited state when it is excited from the v = 0 of the ground state.

My first approach in solving this problem was selecting two transitions (v" = 2 to v' = 7 and v" = 3 to v' = 8). I feel as though my error is in this part of the problem as the question asks for a transition from v = 0 but as far as I can see in the diagram there is no peak for the v = 0 transition.

Following this, I converted the wavelengths for each transition into wavenumbers and then subtracted the wavenumber corresponding to each transition:

$$\nu_{7'0"} = \frac{10^7}{287\ \mathrm{nm}} \approx 34843.205\ \mathrm{cm}^{-1}$$

Then, subtracted $$308\ \mathrm{nm}$$ in wavenumbers from the above value to give $$2375.68\ \mathrm{cm}^{-1}$$ for the transition.

Then using the above numbers I used the following formula to find $$\omega_e$$ and $$\omega_ex_e$$.

$$G\left(v'\right) = \left(v' + \frac{1}{2}\right)\omega_e - \left(v' + \frac{1}{2}\right)^2 \omega_e x_e$$

Then with $$\omega_e$$ and $$\omega_ex_e$$ I used the following formula to find the dissociation energy, $$D_e$$,

$$D_e = {\omega^2 \over 4\omega_ex_e}$$

Then subtracting the zero-point energy from $$D_e$$ to get $$D_0$$ and converting this value into kj/mol just to get an incorrect answer. If anyone could point out where I'm going wrong that would be greatly appreciated.