We can obtain this spectrum pretty consistently.  Oddly enough, we didn’t acidify the MgSO₄ the way Han, et al. describe. We’ll see how this compares to some literature spectra (Hu, et al., Spectrochimica Acta A, vol 51, pgs. 1087-1096, 1995) obtained with borohydride reduced Ag colloids (ours are citrate reduced).

Edit – 6/11/09
It turns out that this is a pretty good spectrum of the plastic microwell plate. Doh!