  We recently used an rf solenoid to study the widths of rf spin resonances
with both unbunched and bunched beams of 2.1 GeV_c polarized protons stored in
the COSY synchrotron. A map, with unbunched beam at different fixed rf-solenoid
frequencies, showed a very shallow possible depolarization dip at the
resonance. Next we made frequency sweeps of 400Hz, centered at similar
frequencies, which greatly enhanced the dip. But, with a bunched proton beam,
both the fixed-frequency and frequency-sweep techniques produced similar maps,
and both bunched maps showed full beam depolarization over a wide region.
Moreover, both were more than twice as wide as the unbunched dip. This widening
of the proton resonance due to bunching is exactly opposite to the recently
observed narrowing of deuteron resonances due to bunching.
