Arranging Reactive Meetings of Cold Radicals
Résumé
In the low-temperature environment of dense interstellar clouds, reactions between unstable radicals can play an important role because stable molecules are often very unreactive under these conditions (1). Radical-radical reactions are also of fundamental importance in gas-phase chemical kinetics (2, 3) but are notoriously hard to study experimentally, because of the need for quantitative control of two potentially unstable reagents at the concentrations necessary to ensure isolation of the reaction, as well as theoretically, because of the complex interactions of two species with unpaired electrons and the lack of a well-defined transition state. On page 1538 of this issue, Daranlot et al. (4) report low-temperature measurements (down to 56 K) of the rate of the N + OH radical-radical reaction, obtained by combining two experimental methods for creating cold radicals; they also performed theoretical calculations that agreed well with their measurements. Their results help to provide a better understanding of how molecular N2 forms in interstellar clouds.