Right-angle geometry

The preferred excitation-detection geometry for the study of macroscopic samples is the right angle geometry [24]. In order to maximize the polarization of the emitted fluorescence, excitation is made with linearly polarized radiation. Tire direction of polarization is usually the vertical direction (see Fig. 7.11). 

Fig. 7.11. Usual geometry for measuring the fluorescence anisotropy (right angle geometry). 

Fig. 4 Brillouin spectra recorded at atmospheric pressure at Tc 5 K in right-angle geometry along the direction (101), nearly parallel to the anthracene long axis (left), and the (101) direction almost perpendicular to this long axis (right). The R. T, OT, and QL indicate, respectively, the Rayleigh elastic line, the transverse mode polarized along the b monoclinic axis, and the quasitransverse and quasi longitudinal modes polarized in the (a,c) plane. The tree spectral range is 39.15 GHz. (From Ref. [18].)...

The instmment sample compartment once again determines what can be studied. Typically, right-angle geometry is used with standard 1 cm square cells for optically-dilute, transparent solutions. In other words, the sample emission is detected at 90° relative to the incident beam this configuration minimises the... 

The typical sample consists in a 1 cm fluorimetric cell, filled with 3-4 ml solution of the compound under study, on which the laser pulse incides after being focused and shaped to have a rectangular section with a cylindrical lens. The analysed volume is a front cyhndrical portion of the excited solution placed at right angle geometry, as represented in Fig. 8.5. 

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