  CMB experiments commonly use maps of Halpha intensity as a spatial template
for Galactic free-free emission, assuming a power law I_nu \propto nu^-0.15 for
the spectrum. Any departure from the assumed free-free spectrum could have a
detrimental effect on determination of the primary CMB anisotropy. We show that
the Halpha-correlated emission spectrum in the diffuse warm ionized medium
(WIM) is not the expected free-free spectrum at WMAP frequencies. Instead,
there is a broad bump in the spectrum at ~50 GHz which is consistent with
emission from spinning dust grains. Spectra from both the full sky and smaller
regions of interest are well fit by a superposition of a free-free and WIM
Draine & Lazarian (1998) spinning dust model, shifted in frequency. The
spinning dust emission is ~5 times weaker than the free-free component at 50
GHz, with the null hypothesis that the Halpha-correlated spectrum is pure
free-free, ruled out at >8 sigma in all regions and >100 sigma for the full sky
fit.
