  We report the first inelastic neutron scattering (INS) experiments of the
resonance in the underdoped regime of Bi2Sr2CaCu2O8+d. The energy of the
resonance is found to be 34 meV and the temperature dependence shows a smooth
evolution through Tc with a remnant persisting in the pseudogap state. Besides
the INS data, we present also angle resolved photoemission (ARPES) spectra
taken on the same crystals. As a function of temperature, the neutron intensity
scales with the square of the ARPES gap estimated by the leading-edge midpoint
at (pi,0). We also show that the energy of the collective mode inferred from
the peak-dip-hump structure compares well with the energy of the resonance.
Based on kinematics, we argue that the correlation of these two energies is
consistent with the absence of bilayer splitting in the electronic dispersion.
