We characterize spinning dust emission in the warm ionized medium by comparing templates of Galactic dust and H \alpha with the 5-year maps from the Wilkinson Microwave Anisotropy Probe .
The H \alpha -correlated microwave emission deviates from the thermal bremsstrahlung ( free-free ) spectrum expected for ionized gas , exhibiting an additional broad bump peaked at \sim 40 GHz which provides \sim 20 % of the peak intensity .
We confirm that the bump is consistent with a modified Draine & Lazarian ( 1998 ) spinning dust model , though the peak frequency of the emission is somewhat lower than the 50 GHz previously claimed .
This frequency shift results from systematic errors in the large-scale modes of the 3-year WMAP data which have been corrected in the 5-year data release .
We show that the bump is not the result of errors in the H \alpha template by analyzing regions of high free-free intensity , where the WMAP K-band map may be used as the free-free template .
We rule out a pure free-free spectrum for the H \alpha -correlated emission at high confidence : \sim 27 \sigma for the nearly full-sky fit , even after marginalizing over the CMB cross-correlation bias .
We also extend the previous analysis by searching the parameter space of the Draine & Lazarian model but letting the amplitude float .
The best fit for reasonable values of the characteristic electric dipole moment and density requires an amplitude factor of \sim 0.3 .
This suggests that small PAHs in the warm ionized medium are depleted by a factor of \sim 3 .