Spectroscopy and Reactions of Hydrocarbon Radicals in 0.4 Kelvin Helium Nanodroplets

Helium nanodroplet isolation (HENDI) has proven to be a versatile technique for many forms of molecular spectroscopy. Helium nanodroplets provide a medium for studying at 0.4 Kelvin, the structure and dynamics of novel systems such as free-radicals, metal clusters, and molecular clusters. In this talk, I will discuss recent progress towards the application of HENDI for the characterization of hydrocarbon radicals and their reactions with O$_2$. The infrared spectra of methyl (CH$_3$), ethyl (C$_2$H$_5$), and propyl (C$_3$H$_7$) radicals are obtained using a high temperature, low pressure, effusive pyrolysis source for doping the droplets. Comparisons to previous gas phase spectroscopy studies reveal a negligible influence of the helium environment on the structure of these radicals. The pyrolysis source and a gas pick-up cell are used to sequentially dope each helium droplet with a single hydrocarbon radical and a single O$_2$ molecule. The resulting products of the low temperature reaction between the radical and O$_2$ are probed spectroscopically downstream from the pick-up zones.