Methane, CH4, has a photodissociation energy of 439 kJ/mole at 298oK, meaning that
CH4 + hv à CH3 + H , hv<274nm
It also has an absorption cross section that starts at ~170nm and increases at lower wavelengths.
My puzzlement is as follows:
1) If the CH4 molecule is decomposed at <274nm, why does it have an absorption profile at lower wavelengths (the molecule should no longer be intact)?
2) If the absorption profile has some kinetic function, why doesnt the profile start near 274nm?
I know that the questions are rooted in my ignorance, but could you please help enlighten me. Thank you in advance.