@article{chen07a,
  author = {Yin-Chu Chen and Jack L. Ferracane and Scott A. Prahl},
  title = {Quantum Yield of Conversion of the Photoinitiator Camphorquinone},
  journal = {Dental Materials},
  year = {2007},
  pages = {655-664},
  abstract = {The primary absorber in dental resins is the photoinitiator, which starts the photo polymerization process. We studied the quantum yield of conversion of camphorquinone (CQ), a blue light photoinitiator, using 3M FreeLight LED and VIP lamps as the light curing units at 5 different irradiances. The molar extinction coefficient, $\varepsilon_{469}$, of CQ was measured to be 46$\pm$2\,cm$^{-1}$/(mol/L) at 469\,nm. We found that the reciprocity of irradiance and exposure time holds for the conversion of the photoinitiator CQ. That is, irradiance $\times$ the exposure time = radiant exposure is a constant. The relationship between the CQ absorption coefficient and the radiant exposure was the same for the 5 irradiances and fit an exponential function: $\mu_{a469}(H) = \mu_{ao} \exp(-H/H_{\mathrm{threshold}})$, where $\mu_{ao}$ is 4.46$\pm$0.05\,cm$^{-1}$, and $H_{\mathrm{threshold}}$=43$\pm$4\,J/cm$^2$. Combining this exponential relationship with CQ molar extinction coefficient and the absorbed photon energy (i.e., the product of the radiant exposure with the absorption coefficient), we plotted CQ concentration [number of molecules/cm$^3$] as a function of the accumulated absorbed photons per volume. The slope of the relationship is the quantum yield of the CQ conversion. Therefore, in our formulation (0.7 w\% CQ with reducing agents 0.35 w\% DMAEMA and 0.05 w\% BHT) the quantum yield was solved to be 0.07$\pm$0.01\, CQ conversion per absorbed photon.},
}