Polarization Effects in the Isospin-Coupled Reaction Channels<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>+<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Zr</mml:mi></mml:mrow><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>91</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>+<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi mathvariant="normal">Nb</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="normal">IAS</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow><mml:mrow/><mml:mrow/><mml:mprescripts/><mml:mrow/><mml:mrow><mml:mn>91</mml:mn></mml:mrow><mml:mrow/><mml:mrow/></mml:mmultiscripts></mml:mrow></mml:math>

The analyzing-power and differential cross-section excitation functions for the reaction $p$ + $^{91}\mathrm{Zr}$ have been measured at 150\ifmmode^\circ\else\textdegree\fi{} in the energy range from 10.0 to 14.9 MeV, which spans the thresholds of the ($p, n$) quasi-elastic and quasi-inelastic reaction channels leading to the production of the analogs in $^{91}\mathrm{Nb}$ of the $^{91}\mathrm{Zr}$ target ground state and ${\frac{5}{2}}^{+}$ (1.46 MeV) excited state, respectively. A pronounced variation in the analyzing power is observed in the ($\stackrel{\ensuremath{\rightarrow}}{p}, {d}_{0}$) exit channel at just the energy regions where charge-exchange coupling is expected to occur due to the opening of the quasi-elastic and quasi-inelastic channels. Somewhat less expected is the change in analyzing power observed in the elastic proton channel in the vicinity of the quasi-elastic and quasi-inelastic thresholds. Sharp resonance structures are observed in the analyzing-power and differential cross-section excitation functions for the ($\stackrel{\ensuremath{\rightarrow}}{p}, {d}_{0}$) channel near the quasi-elastic and quasi-inelastic thresholds which are not readily observable in the elastic channel. The analyzing power for the ($\stackrel{\ensuremath{\rightarrow}}{p}, n\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{p}$) process has been measured at a number of energies in this region and found to be consistent with zero.