Dissociation of Cl2 .... Help?

The energy required to dissociate the Cl2 molecule to chlorine atoms is 239 kJ/mole of Cl2 @ 25 degrees C. If the dissociation of the one molecule was accomplished by the absorption of a single photon whose energy was exactly the energy required, what would be its wavelength in nanometers? from what part of the electromagnetic spectrum would it come? (UV, visable, IR)