Knowledge Bank

Nitryl bromide ($BrNO2$) formed by heterogeneous reaction on polar stratospheric clouds and on sea-salt particles in the marine troposphere. However, no rotationally resolved spectra have been reported up to now, and nothing is known about rotational constants, structure, and force field of $BrNO2$. In fact, the only observations of $BrNO2$ in the gas phase were possible using flow experiments with gaseous $N2O5$ flowing over NaBr particles. In this study, a different approach was used. By reaction of highly diluted gaseous $ClNO2$ with an aqueous $Br-$ solution, $BrNO2$ was formed and trapped at low temperature. The crude product was purified by trap-to-trap condensations and fractional sublimation in vacuo. High-resolution infrared spectra of the $\nu 4$ band of $BrNO2$ around $1660cm-1$ were measured with resolutions of up to $0.002cm-1$, using the Bruker IFS-120HR FTS at University of Hannover. For the first time, rotational constants for the $\mathrm{<mrow\; data-mjx-texclass="ORD">79</mrow>}BrNO2$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">81</mrow>}BrNO2$ isotopomers were determined for the $\nu 4$ and ground vibrational states. The constants were used for determination of a first substitution structure and, together with infrared band centers, the harmonic force field of $BrNO2$.