  Measurement of magnetic fields in dense molecular clouds is essential for
understanding the fragmentation process prior to star formation. Radio
interferometric observations of CCS 22.3 GHz emission, from the starless core
TMC-1C, have been carried out with the Karl G. Jansky Very Large Array to
search for Zeeman splitting of the line in order to constrain the magnetic
field strength. Toward a region offset from the dust peak, we report a
detection of the Zeeman splitting of the CCS 2_1 - 1_0 transition, with an
inferred magnetic field of ~2 mG. If we interpret the dust peak to be the core
of TMC-1C, and the region where we have made a detection of the magnetic field
to be the envelope, then our observed value for the magnetic field is
consistent with a subcritical mass-to-flux ratio envelope around a core with
supercritical mass-to-flux ratio. The ambipolar diffusion timescale for the
formation of the core is consistent with the relevant timescale based on
chemical modeling of the TMC-1C core. This work demonstrates the potential of
deep CCS observation to carry out future measurements of magnetic field
strengths in dense molecular clouds and, in turn, understand the role of the
magnetic field in star formation.
