For optimally doped Bi 2212, scattering rates in the normal state are found
to have a linear temperature dependence over most of the Fermi surface. In the
immediate vicinity of the (1,0) point, the scattering rates are nearly constant
in the normal state, consistent with models in which scattering at this point
determines the c-axis transport. In the superconducting state, the scattering
rates away from the nodal direction appear to level off and become
temperature-independent.Comment: published version, 4 pages, 3 eps figures + 1 jpg figur