On the shape of derivative curve which is conceivable to be formed by superposition of a broad and a narrow absorption band the following results were obtained: A pair of peaks of the inner component disappears when
r, i.e. the ratio of peak-height of the narrow band and the height of the level at the same point, amounts to 0.7
3 and 0.4
4 for the Gaussian and the Lorentzian line shapes, respectively. For the modulation effect the distance, at which the inner peaks disappear, is approximately given by
d/_??_, where
d is the distance of the peak and
r' the ratio of height at the inner peak point.
On the symmetrical doublet line, where the distance between the peaks is given by 2. These peaks disappear when the half width increases beyond 2 and 2_??_ for the Gaussian and the Lorentzian, respectively. The observed derivative curve tends to show a single line when the modulation width exceeds 1.3 times of the peak-to-peak distance, while variation of the derivative curve is fractionally small so far as the modulation width is approximately half of the distance.
Furthermore, the modulation effect for the derivative curve of a single line was studied experimentally.
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