fluorescent spectrometry basic concept with animated jablonski diagram

1. Fluorescent spectrometry
Presented to :
Dr.lubnaRasheed
Presented by :
AimenAzeem (Bsf1700001)

2. What is fluorescence ?
• Molecules absorb photons and are excited to a higher
electronic state
• The absorbed energy can be released by emission of
a photon of light
• The molecule stays in an excited state for 1 – 10n sec
before emission

3. Related terms:
• An atom or molecule that fluoresces is termed a fluorophore.
• Fluorometry is defied as the measurement of emitted florescent
light.
• Fluorescence spectroscopy is a type of electromagnetic
spectroscopy which analyzes fluorescence from a sample.

4. Related terms:
The difference between the maximum wavelength of the
excitation light and the maximum wavelength of the emitted
florescence light is a called Stokes shift .

5. History :
• JABLONSKI: The father of fluorescence spectroscopy
• The processes that occur between absorption and
emission of light was explained by Prof. Alexander
Jablonski
• The first observation of fluorescence from a quinine
solution in sunlight was reported by Sir John
Frederick William Herschel in 1845.

6. Singlet and triplet states
• Ground state –two electrons per orbital; electrons
have opposite spin and are paired
• Singlet excited state Electron in higher energy
orbital has the opposite spin orientation relative to
electron in the lower orbital
• Triplet excited state The excited valence electron
may spontaneously reverse its spin (spin flip). This
process is called intersystem crossing. Electrons in
both orbitals now have same spin orientation

7. Ground state Excited singlet state Excited triplet state
Ms =2(S ) + 1 = 0
2(S ) + 1 = 0
2( +1
2
−
1
2
) + 1 = 0
2(0) + 1 = 1
2(S ) + 1 = 0
2(+1
2
+
1
2
) + 1 = 0
2 ( 1) + 1 = 3

8. Jablonski diagram
So
2
1
0
hv
S1
S2
Absorption
Internal
conversion
hvf
hvp
T1
Phosphorescence

9. Many
wavelengths
Single
wavelength
Sample cell
Single
wavelength

10. Thanks for u
time
(Any question )