  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 $\nu_1$ 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 $\nu_1$
mode of propargyl-bromide is also reported. The future application of these
methods for the production of novel radical clusters is discussed.
