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Write down a kinetic equation (net rate law) for the concentration change of excited oxygen atoms with time d[0]/dt where t represents time.

Integrate your rate law, to afford an analytical expression showing the actual variation of the excited oxygen atom concentration with time, given that no o* exists prior to t = 0.

HINT: you may find that making assumptions that I and [M] are independent of time to be helpful!

Use the steady-state approximation and your kinetic equation to determine the steady-state concentration

of excited oxygen atoms., and identify under what conditions the actual variation of the excited oxygen

atom concentration corresponds to the steady-state variation.

Then, estimate the minimum illumination time required for the non-steady state and steady-state

concentrations to be identical to within 1%.

Comment on whether the steady-state hypothesis is a good approximation for the atmospheric behaviour of

excited oxygen atoms where the solar intensity changes over periods of hours.

Question A2: The ground state oxygen atom

Write down a kinetic equation (net rate law) for the concentration change of ground-state oxygen atoms

with time, do, where t represents time, neglecting equation (A.2).

Integrate your rate law, to afford an analytical expression showing the actual variation of the ground-state

oxygen atom concentration with time, under conditions of constant irradiation, and that all species M are

present in excess. Make sure you identify appropriate boundary conditions.

Use the steady-state approximation and your kinetic equation to determine the steady-state concentration

of ground-state oxygen atoms.

Then, identify whether the steady-state hypothesis is a suitable approximation to apply to ground-state

oxygen atoms in atmospheric modelling.

Comment on any similarities or differences you have found in the application of the steady-state

approximation for the reactive intermediates (O and O*) considered in Questions A1 and A2.