[Hello12]

Hi i am trying to work out the lowest ionisation energy of CO2 by using its maximum kinetic energy of the emitted photoelectrons being 7.43ev. My attempt includes using 1/2mv^2+I=hv but i dont think this is correct. Any guidence would be appreciated

[Enthalpy]

Do you have more data, like for instance the photon's energy?

Because if the photons are gammas, you can get electrons with MeV energy, be they from CO₂ or anything else.

If the question is like I suppose, it must be some energy conservation rule, but to be accurate, remember that the ion also has some impulse hence kinetic energy as well. With gammas, you'd need the photon's impulse as well, since the impulse-to-energy relationship resembles for any relativistic particle.

[Hello12]

I worked out the energy of the photon to be 21.23ev