  We present an assessment of the (6s^{2})1S0 -> (6s7s)3P0 clock transition
frequency in 199Hg with an uncertainty reduction of nearly three orders of
magnitude and demonstrate an atomic quality factor, Q, of ~10^(14). The 199Hg
atoms are confined in a vertical lattice trap with light at the newly
determined magic wavelength of 362.5697 +/-0.0011 nm and at a lattice depth of
20Er. The atoms are loaded from a single stage magneto-optical trap with
cooling light at 253.7 nm. The high Q factor is obtained with an 80 ms Rabi
pulse at 265.6 nm. The frequency of the clock transition is found to be 1 128
575 290 808 162.0 +/-6.4 (sys.) +/-0.3 (stat.) Hz (fractional uncertainty =
5.7x10^(-15)). Neither an atom number nor second order Zeeman dependence have
yet to be detected. Only three laser wavelengths are used for the cooling,
lattice trapping, probing and detection.
