Knowledge Bank

Reactions between RO$2$ and HO$2$ are important in the gas phase oxidation of volatile organics in the atmosphere. The rate constants for the reactions of HO$2$ + C$2$H$5$O$2$, and C$2$H$5$O$2$ + C$2$H$5$O$2$ were measured using a novel approach to radical radical reactions that employs two independent spectroscopic probes. HO$2$ was monitored at 6638.2 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ using near-IR diode laser WM spectroscopy, and C$2$H$5$O$2$ was monitored at 250 nm using UV absorption. Experiments were run under conditions relevant to the upper troposphere (221-298 K and 50-400 Torr). Measurements of the rate constants for both reactions as well as a measurement of the branching fraction leading to the alkoxy channel of the C$2$H$5$O$2$ self reaction will be discussed. Preliminary results are: k = $(6.4\pm 1.4)\times 10-13$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ molec$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ s$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ Exp(($601\pm 120$)/ T ), k = $(1.10\pm 0.20)\times 10-13$ cm$\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ molec$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ s$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ independent of temperature, and a branching fraction of $0.32\pm 0.13$.