CS CHEMISTRY IN THE BIPOLAR NEBULA CRL-2688

High spatial-resolution observations of the protoplanetary nebula CRL2 688 were made by the CS J =1-0 and J =2-1 lines with the Nobeyama Mill imeter Array with angular resolutions of 6 '' x6 '' and 3 '' x3 '', re spectively. The mapping observations reveal that strong CS peaks in th e J =2-1 line are located symmetrically at both sides of the optical d ark lane at the center, though the CS J =1-0 distribution is rather ro und. These CS peaks seem to be slightly misaligned from the optical bi polar axis. A modeling of the CRL 2688 envelope results that the densi ty distribution is nearly spherically symmetric but the abundance of C S is enhanced near the polar regions. The increase of the CS abundance near the poles can be explained by the chemistry of sulfur containing molecules in the postshocked region in the high-velocity flow.