Accuracy Evaluation of a $^{87}\hbox{Sr}$ Optical Lattice Clock

In this paper, we report the observation of the higher order frequency shift due to the trapping field in a
⁸⁷
Sr optical lattice clock. We show that at the magic wavelength of the lattice, where the first order term cancels, the higher order shift will not constitute a limitation to the fractional accuracy of the clock at a level of 10
^-18
. We also report an accurate frequency measurement of the clock transition. The frequency is determined to be v
¹
S
₀
-
³
P
₀
= 429 228 004 229 879 (5) Hz with a fractional uncertainty that is comparable to state-of-the-art optical clocks with neutral atoms in free fall