  We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a
micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure
enhances the peak amplitude of the in-gap THz electric field by a factor of
~170. Above an in-gap E-field threshold amplitude of ~10 MVcm-1, THz-induced
field electron emission is observed (TIFEE) as indicated by the field-induced
electric current across the dipole antenna gap. Field emission occurs within a
fraction of the driving THz period. Our analysis of the current (I) and
incident electric field (E) is in agreement with a Millikan-Lauritsen analysis
where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate
that the electrons are accelerated to a value of approximately one tenth of the
speed of light.
