Free Radicals in Superfluid Liquid Helium Nanodroplets: A Pyrolysis Source for the Production of Propargyl Radical

Abstract

An effusive pyrolysis source is described for generating a continuous beam of radicals under conditions appropriate for the helium droplet pick-up method. Rotationally resolved spectra are reported for the $ν_1$ vibrational mode of the propargyl radical in helium droplets at 3322.15 cm$^{-1}$. Stark spectra are also recorded that allow for the first experimental determination of the permanent electric dipole moment of propargyl, namely -0.150 D and -0.148 D for ground and excited state, respectively, in good agreement with previously reported ab initio results of -0.14 D [1]. The infrared spectrum of the $ν_1$ mode of propargyl-bromide is also reported. The future application of these methods for the production of novel radical clusters is discussed.