Fig. 3From: Fast decay of 23S1 positronium atoms in an MgO lined cavitya Example of lifetime spectra taken with LYSO detector for 3.5 keV positrons impinging on SiO2 (Sig. and Back.) and, b Background subtracted spectra showing examples of photoionization, and \(2\,^{3}\mathrm {S}_{1}\) production, as described in the text. The signal and background spectra in (a) correspond to the photoionization signal in (b)Back to article page