Knowledge Bank

A flow tube reactor was built to provide an experimental device to measure electronic quenching rate constants for singlet delta oxygen ($\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta 02$) in the gas phase and at the wall of the tube. Experiments with a cylindrical Pyrex tube have been completed. The source of $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta O2$ was a microwave cavity operated at 2.45 GHz. The detection system for the $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Delta O2$ consisted of an intrinsic germanium infrared detector, filters, fiber optics, and associated electronics. The emission from the $O2$ (a-X) transition at $1.268\mu$ was transmitted from observation stations at the flow tube reactor by means of a fiber optic cable through a band pass filter to the detector. The chopped signal from the detector was passed into a lock-in amplifier system. The digitized signal was then passed into an IBM PC AT computer for storage and subsequent analysis. A thorough error analysis was performed on the data. The room temperature quenching coefficient for the Pyrex surface was determined to be $7-2.5-0.5\times 10-5$ and the gas phase electronic quenching rate constant for quenching with ground state oxygen was determined to be $k=3.1-1.8\times 10-18cc/sec$. The kinetic and mathematical models which were used to determine the values for the rate constants will be discussed.