In this report, we introduce the basic principles of CPL measurements, which
include the meaning of the signals obtained in CPL spectroscopy, the type of
equipment used, the calibration methods, and measurement examples.
14.2 Introduction to CPL
CPL can be best described by comparing it to CD, which involves a difference in the
amount of absorption of left- and right-handed circularly polarized light by an
optically active substance, as shown in Fig. 14.1a. In contrast, as shown in
Fig. 14.1b, CPL spectroscopy measures the difference in the intensity of left- and
right-handed circularly polarized fluorescence during optical excitation of a sample.
The magnitude of the CD and CPL signals is expressed by Eqs. (14.1) and (14.2),
respectively.
(a) CD
Sample
Excitation
light
Unpolarized light
CPL
Sample
Incident
light
(b) CPL
Transmitted
light
Right-handed circularly
polarized light
Left-handed circularly
polarized light
Fig. 14.1 Comparison of CD (a) and CPL (b)
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S. Suzuki