Asked Sep 10, 2019

Why are wavlength maxima different for UV-Vis and Fluorescence?



Expert Answer

Step 1

Any molecule has quantized electronic levels.  These levels differ largely in energy as compared to the vibrational and rotational levels.  Therefore, each electronic levels contains many vibrational and rotational levels.

UV-Vis measures the absorption of light in this range, while fluorescence measures the light emitted by a sample in this range after absorbing light at a higher energy than it is emitting.

Step 2

The difference between UV-Vis and fluorescence is that instead of having a white light pass directly through the...


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excited vibrational states (excited rotational states not shown) Sn A-photon absorption F-fluorescence (emission) P phosphorescence S-singlet state T-triplet state IC internal conversion ISC intersystem crossing S2 IC -T2 ISC -T1 A So te ectronic ground sta el Energy


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