Transcript Stroboscopic Method - Zakład Fizyki Chemicznej

Course Material on the Web
• Lecture 1 at
http://www.zfch.amu.edu.pl/publikacje.html
http://www.zfch.amu.edu.pl/Lecture 1.ppt
http://150.254.84.227/HUG (uncorrected version)
• Lecture 3 (seminar by Isvan Robel) at
http://www.nd.edu/~pkamat/femto.html
• Lecture 4 material at
http://www.rcdc.nd.edu/compilations/Tta/tta.pdf
Lecture 3
Pump-Probe Femtosecond Laser
Isvan Robel
Physics
Graduate student
at Notre Dame
Review of Lecture 1
• Excited states and free radicals act like
distinct chemical species.
• However, it is important to characterize
their time-dependence in order to utilize
their energy content.
Review of Lecture 1
Jabłonski - diagram
ISC
S1
IC
excited
singlet state
singlet
ground state
T1
fluorescence
vibrational
relaxation
S1
ISC
S0
(heat)
phosphorescence
S0
excited
triplet state
T1
State Picture
Orbital Picture
Review: Robinson-Frosch
Rate of Radiationless Transitions
dP(nm)/dt = (42/h) |Vmn|2 FC (Em)
• Three factors
– Electronic matrix element
– Franck-Condon factors
– Density of final states
Review: Franck-Condon Effect
Sn
S1
S0
Review: El-Sayed’s Rule
• Selection Rule for Intersystem Crossing
• Transitions between a singlet state and a
triplet state of the same orbital
configurations are slower than that
between states having different orbital
configurations.
• Examples, ISC transition 1n,*  3,* is
much faster than 1,*  3,*
Characteristics of
Radiationless Transitions
•
•
•
•
Kasha’s Rule
El-Sayed’s Rule
Deuterium Effect
Wavelength Independence of
Luminescence
• Energy Gap Law
• Competitive First-Order Kinetics
Lecture 2
• Part 1: Fluorescence Lifetimes using
Stroboscopic Method
• 10-minute break
• Part 2: Fluorescence Lifetimes using TimeCorrelated Single-Photon Counting TCSPC
Stroboscopic Method
• Aleksander Siemiarczuk, et al.
Reviews of Scientific Instruments 63,
1710-1716 (1992)
• Commercial Instrumentation by PTI
Sample & Excitation
Lamp
PMT
Sample
Excitation
Monochromator
Fluorescence
Monochromator
Photomultiplier Tubes (PMT)
h
e
Photocathode of PMT
Dynodes of PMT
Ne
Anode of PMT
Detection within the Time
Window of the Stroboscopic
Pulse
Stroboscopic Method
Pulsing the PMT Detection
Photocathode of PMT
Dynodes of PMT
Anode of PMT
Creation of Stroboscopic Pulse
Long Lifetime Sample
Short-lifetime Sample