1. Luminescence Spectrometry
Molecular
Luminescence Spectrometry
Chap 15

2. Factors Affecting Fluorescence
and Phosphorescence
Quantum Yield
Expressed in terms of rate constants:
where knr = kvib + kic + kec +kisc + kpd + kd
varies from 0 to 1

3. Factors Affecting Fluorescence
and Phosphorescence
Transition Types in Fluorescence
σ* → σ Transitions (seldom observed)
π* → π Transitions (most common, higher )
π*→ n (longer lifetime, lower )
Fluorescence typically from lowest vib. level, vʹ = 0,
of excited electronic state

4. Factors Affecting Fluorescence
and Phosphorescence
Fluorescence and Structure
Most intense from aromatic π* → π transitions
increases with:
number of fused rings
rigidity of structure (lowers kic)
Fluorescence and Temperature, Solvent, & pH
All must be monitored to minimize kec

5. Excitation and Emission Spectra of Phenanthrene
Fig. 15-5

6. Components of a Fluorometer or Spectrofluorometer
Fig. 15-8 λ λ

7. Filter Fluorometer Fig. 15-10
Less expensive,
rugged, good for
concentration measurements

8. Components of a Spectrofluorometer
Fig
∼300 W at nm

9. Fig
Resulting emission is isotropic
If source is at fixed λ and monochromator is scanned an emission spectrum results.
If source is scanned, and monochromator is at a fixed λ, an excitation spectrum results.

10. Fluorescence Spectra for 1 ppm anthracence in alcohol
Fig. 15-9
Fluorescence Spectra for
1 ppm anthracence in alcohol
Emission Spectrum:
Constant λex
Variable
Info on vib levels in S1
λem
Excitation Spectrum
Constant λem
Variable λex
Info on vib levels in S0