## front surface geometry

in luminescence
https://doi.org/10.1351/goldbook.F02535
A system where excitation and observation are from the same face of the sample ($$\alpha\ \angle\ 90^{\,\unicode{x26ac}}$$, $$\beta\ \angle\ 180^{\,\unicode{x26ac}}$$ where $$\alpha$$ = @A00346@ of incidence of the exciting beam on the plane surface of the sample, and $$\beta$$ = @A00346@ between the exciting direction and observation direction.)
Source:
PAC, 1984, 56, 231. (Nomenclature, symbols, units and their usage in spectrochemical analysis-Part VI: molecular luminescence spectroscopy) on page 244 [Terms] [Paper]