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Reduced scattering coefficients of the two alumina materials (pore diameters of 70 and 18 nm, respectively). At 760 nm, the difference in scattering is a factor 16 ( against ). Interestingly, the sample with the larger pores exhibit a Rayleigh-type scattering decay, while the sample with the smaller pores only show a behavior. This suggests that the major scattering contribution in the latter sample originates from collective effects rather than from individual 18 nm pores.
Comparison of experimental line shapes of free oxygen and oxygen confined in 70 nm pores of -alumina. Lorentzian profiles (red, smooth) are fitted to experimental data (black, noisy). Fitted line shape halfwidths, , are stated in the graph and marked by vertical dashed lines. The fitted path length through pores, , assumes an oxygen concentration of 20.9%. For the -alumina sample, the detected power was .
Intensity corrected WMS signals obtained from the -alumina sample with 18 nm pore diameters (noisy, black solid) together with fitted WMS simulations for Lorentzian line shapes (smooth, red solid). The detected power was . The tight confinement causes significant line broadening, here illustrated by a comparison to normalized WMS signals of free oxygen (dashed red, ). Stated HWHM and path length through pores refer to fitted values ( deviation of three repetitions). Note the discrepancy in fitted values between first and second harmonic, showing that a Lorentzian is an improper line shape model.
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