  We demonstrate nanometer-scale spatial control of inter-atomic interactions
in a Bose-Einstein condensate of ytterbium(Yb). A pulsed optical standing wave,
tuned near an optical Feshbach resonance varies the s-wave scattering length
continuously across the standing wave pattern. The modulated mean-field energy
with a spatial period of every 278 nm is monitored by a diffraction pattern in
a time-of-flight image. We observe a wide scattering length control of up to
160 nm. The demonstrated spatial modulation of the scattering length proves
that the high resolution control of atomic interactions is possible.
