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Advanced Femtosecond Laser Physics: Review and Techniques

Explore the fundamentals of femtosecond laser physics, covering excited states, free radicals, radiationless transitions, and fluorescence lifetimes. Understand key concepts such as the Jabłonski diagram, Franck-Condon effect, El-Sayed's rule, and Kasha's rule. Learn about practical applications and instrumentation for fluorescence measurements using stroboscopic methods and time-correlated single-photon counting. Enhance your knowledge with insights from esteemed physicists.

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Advanced Femtosecond Laser Physics: Review and Techniques

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  1. 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

  2. Lecture 3 Pump-Probe Femtosecond Laser Isvan Robel Physics Graduate student at Notre Dame

  3. 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.

  4. ISC IC excited singlet state S1 S1 singlet ground state S0 T1 ISC fluorescence vibrational relaxation (heat) phosphorescence excited triplet state S0 T1 Review of Lecture 1 Jabłonski - diagram State Picture Orbital Picture

  5. Review: Robinson-FroschRate 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

  6. Review: Franck-Condon Effect Sn S1 S0

  7. 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,*

  8. Characteristics ofRadiationless Transitions • Kasha’s Rule • El-Sayed’s Rule • Deuterium Effect • Wavelength Independence of Luminescence • Energy Gap Law • Competitive First-Order Kinetics

  9. Lecture 2 • Part 1: Fluorescence Lifetimes using Stroboscopic Method • 10-minute break • Part 2: Fluorescence Lifetimes using Time-Correlated Single-Photon Counting TC-SPC

  10. Stroboscopic Method • Aleksander Siemiarczuk, et al. Reviews of Scientific Instruments63, 1710-1716 (1992) • Commercial Instrumentation by PTI

  11. Sample & Excitation Lamp PMT Sample Fluorescence Monochromator Excitation Monochromator

  12. Photomultiplier Tubes (PMT) h Photocathode of PMT e Dynodes of PMT Ne Anode of PMT

  13. Detection within the Time Window of the Stroboscopic Pulse

  14. Stroboscopic Method

  15. Pulsing the PMT Detection Photocathode of PMT Dynodes of PMT Anode of PMT

  16. Creation of Stroboscopic Pulse

  17. Long Lifetime Sample

  18. Short-lifetime Sample

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