Concept explainers
Interpretation:
The points based on which a fluorescence emission spectrum and a fluorescence excitation spectrum can be differentiated needs to be explained. From the two spectrums, the one that resembles an absorption spectrum more closely is to be stated.
Concept introduction:
Fluorescence is a word used for the members of the luminescence family. In this family, the molecules of a substance can emit their own light with the help of electronically excited states which can be formed by physical, chemical or mechanical mechanism.

Explanation of Solution
There are two fluorescence spectrums namely the fluorescence emission spectrum and the fluorescence excitation spectrum. The difference between the two is shown below.
Fluorescence Emission Spectrum | Fluorescence Excitation Spectrum |
The wavelength for excitation does not vary. It is constant. | The wavelength for excitation varies. It is not constant. |
The intensity of emission changes according to the change in emission wavelength. | The intensity of emission does not change. It is measured at one wavelength. |
In the fluorescence excitation spectrum, the emission intensity is proportional to the absorbance of the molecule. This phenomenon makes it closer to absorption spectrum rather thanfluorescence emission spectrum.
Thus, the fluorescence excitation spectrum is closer to an absorption spectrum.
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Chapter 15 Solutions
Principles of Instrumental Analysis, 6th Edition
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