(1-1)          1 mole of Cl2 comprises Avogadro’s number of molecules. So the energy required to break one individual Cl-Cl bond:

E  =  243 000 Jmol-1 / 6.023 x 1023 mol-1  =   4.04 x 10-19 J

      The photon wavelength that corresponds to this energy is given by:

λ   =  hc /E   = 6.626 x 10-34 Js  x  3.00 x 108 ms-1 /  4.04 x 10-19 J  =   4.93 x 10-7 m  =  493 nm

This corresponds to a photon of blue-green light. Your red laser photons have a longer wavelength than this (633 nm) and therefore their energies are lower than that required to break the bond. However, Cormorant’s disco-light photons have a shorter wavelength (350 – 400 nm) and therefore have more than enough to break the bond.