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Results and discussion

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CN(X ²Σ⁺), and NCO(X ²Π) formation

The CN(X) radicals were produced by the direct reaction between O(¹D) and CF₃CN and not formed by other reaction paths such as the relaxation of CN(A).

LIF spectrum of the CN(B−X) transition observed at the delay time 15 µs (upper trace) and simulated spectrum (lower trace).

Because no standard value of the quantum yield for the CN(X) formation in the reaction of O(¹D) has been determined, the branching ratio for this reaction pathway was not measured.

NCO(X ²Π) formation

The NCO radicals were not observed in the reaction of O(¹D) with CF₃CN on the same time scale as the production of O(³P) and CN(X) productions.

LIF spectrum of the NCO(A−X) transition observed at the delay time 100 µs.

The LIF signal intensity did not reach an asymptotic value until the delay time of ca. 100 µs. Since this time scale is much larger than that of production rates of O(³P) and CN(X), the NCO(X) radical cannot be formed by the primary process of O(¹D) + CF₃CN.

Total rate constant for the removal of O(¹D)

The value measured here was k_total = 1.3 ×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The data of the O(¹D) decay rates and the O(³P) rise rates are consistent with each other.

Typical temporal profile of O(1D). The horizontal scale is the delay time between photolysis and probe laser pulses. The solid line is the least-squares fit to the observed profile by the exponential decay function.

Quantum yield for the electronic quenching of O(¹D)

When the delay time was long enough to quench O(¹D) completely, the signal intensity of O(³P) approaches an asymptotic value after 15 µs. The asymptotic signal intensity measured in the reaction O(¹D) + CF₃CN was normalized by the comparison with that in the reaction O(¹D) + N₂ under the same initial concentration of O(¹D). The quantum yield φ_q, i.e the ratio obtained by this comparison, was 0.14. The quenching rate constant, k_q = k_total φ_q, is calculated to be 1.8 ×10⁻¹⁰ cm³ molecule⁻¹ s⁻¹.

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