specular reflectance (reflection factor), \(\rho\)

in optical spectroscopy
https://doi.org/10.1351/goldbook.S05851
@[email protected] specularly reflected from the surface of a system, \(P_{\mathrm{refl}}\), divided by the incident @[email protected], \(P_{0}\): \[\rho =\frac{P_{\mathrm{refl}}}{P_{0}}\]
Source:
PAC, 1985, 57, 105. (Names, symbols, definitions and units of quantities in optical spectroscopy (Recommendations 1984)) on page 115 [Terms] [Paper]