The signal‐to‐noise ratio in linear dichrosim measurements using the polarization modulation technique is hindered by the presence of fictitious signals originating from briefringence and polarization sensitivity in the optical components. We have shown both theoretically and experimentally that such artifacts resulting from optical elements after the sample can be removed by placing a second modulator immediately after the sample. The second modulator, which must be of a different frequency than the first, and which must be adjusted to a specific that the synchronous time average of the fictitious signal is zero. The true linear dichroism signal is unaffected. In wavelength regions where thjere are no fictitious signals. The scrambler neither introudces artifact signals nor does it affect the real signals. Fictitious signals due to imperfections in optical components before or within the sample itself cannot be nulled in the same manner.

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For a detailed discussion on the method of calculation, see
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6.
The operation Iac/Idc can be performed by varying the photomultiplier tube’s gain so as to maintain a constant Idc. Under this condition the photomultiplier’s m1 signal is proportional to the Iac/Idc ratio with a proportional constant of I/Idc.
7.
J. C.
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8.
The two modulator frequencies ωm1 and ωm2 must satisfy the inequality, τ≫2π|ωm̅̇1−ωm2−1|, where τ is the lock‐in’s integration time constant.
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