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Title: The study of chemiluminescent reactions in the gas phase
Author: Izod, Thomas Paul John
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 1969
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The two lowest lying singlet electronic states of molecular oxygen O2(1Δg) and O2(1Σg+) are present in the atmosphere and undergo optical transitions to the ground state molecule giving rise to the atmospheric bands:

  • O2(1Σg+) ↔ O2(3Σg-) (O,O) 762 nm

and the infra-red atmospheric bands:

  • O2(1Δg) ↔ O2(3Σg-) (O,O) 1268 nm.

Possible mechanisms for the production of the excited species were studied in the laboratory. The reactions were carried out in time resolved flow systems and the species observed by their optical emission with the aid of photomultipliers and photo conductors in conjunction with phase sensitive detection circuitry. The ultra violet photolysis of ozone with λ = 253.7 nm was studied as a source of O2(1Σg+) and O2(1Δg). O2(1Δg) was observed in the photolysis of ozone-oxygen mixtures with λ = 253.7 nm and its production was attributed to the energy transfer process:

  • O(1D) + O2(3Σg-) → O(3P) + O2(1Δg).
O2(1Σg+) was observed in a system involving the photolysis of oxygen with λ = 147 nm by an analogous reaction:
  • O(1D) + O2(3Σg-) → O(3P) + O2(1Σg+)

The atom recombination reaction:

  • O(3P) + O(3P) + M → O2(singlet) + M

and the chemi luminescent reaction:

  • NO + O3 → NO2 + O2 + hν

were studied but found not to produce significant quantities of excited molecular oxygen. The excited species have relatively long lifetimes and generally undergo physical or chemical deactivation reactions in preference to radiative transitions. The reactions of O2(1Σg+) and O2(1Δg) with ozone:

  • O3 + O2(1Σg+) → 2O2 + O(3P)
  • O3 + O2(1Δg) → 2O2 + O(3P)

and the quenching reactions:

  • O2(1Σg+) + M → O2 + M

where M = O2, N2 and Ar were studied and rate constants evaluated. A value for the efficiency of deactivation of O2(1Σg+) at a pyrex surface was also obtained and the rate of the energy pooling process O2(1Δg) + O2(1Δg) → O2(1Σg+) + O2(3Σg-) was estimated.

The rates of the following O(1D) atom reactions:
  • O(1D) + N2 → O(3P) + N2
  • O(1D) + Ar → O(3P) + Ar
  • O(1D) + O3 → O2 + O2
  • O(1D) + O2 → O2(1Σg+) + O(3P)
  • O(1D) + O2 → O2(1Δg) + O(3P)

were estimated. Calculations were carried out to test the importance of the various mechanistic schemes studied as sources of excited singlet oxygen in the atmosphere, In addition the major loss processes of excited oxygen molecules and atoms were calculated and the results compared with atmospheric data.

Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available