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Pump-probe spectroscopy: fast versus slow nuclear dynamics

“Born Oppenheimer” approximation:. H-O stretch motion (fast subsystem):. Nuclear Hamiltonian of slow subsystem:. Pump-probe spectroscopy: fast versus slow nuclear dynamics. 2D. 1D. Probe field:. Pump-probe spectroscopy in the framework of BO. Pump field. Water Dimer.

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Pump-probe spectroscopy: fast versus slow nuclear dynamics

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  1. “Born Oppenheimer” approximation: H-O stretch motion (fast subsystem): Nuclear Hamiltonian of slow subsystem: Pump-probe spectroscopy: fast versus slow nuclear dynamics 2D 1D

  2. Probe field: Pump-probe spectroscopy in the framework of BO Pump field Water Dimer mixes two lowest OH vibrational states Dynamics of femtosecond O-O stretch motion

  3. Property Toolbox magnetic internal external electric linear time-dep nonlinear Time-indep

  4. a = 80 nm a = 13 nm Dependence of collisional dephasing rate on photon detuning Homogeneous broadening Life-time broadening Collisional dephasing rate Kenji Kamada measurements

  5. Example: PRL-101 Ab initio results: AM1 geometry/6-31G*/DFT Quadratic Response 1280 GM at G = 0.1 eV

  6. Non-linear pulse propagation T (1 W/cm2) = 0.994 L = 5 mm t = 140 fsec G = 0.1 eV

  7. Non-linear pulse propagation

  8. Non-linear pulse propagation Exponential decay of red wing of linear absorption profile In case of Lorentzian decay TPA cross section is unrealistically high Inhomogeneous broadening of TPA spectra is not considered

  9. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Sensor ProtectionProtection against lasers

  10. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 The Project Group/Co-Workers • Dr. Bertil Eliasson, UmU, Sweden • Marcus Carlsson, PhD student • Dr. Eva Malmström, KTH, Sweden • Robert Vestberg, PhD student • Robert Westlund, PhD student • Dr. Stephane Parola, UCBL, France • Marcus Örtenblad, PhD student Preparation of materials Modeling • Prof. Hans Ågren, KTH, Sweden • Oscar Rubio Pons, PhD student • Peter Cronstrand, PhD student • Dr. Patrick Norman, LiU, Sweden • Johan Henriksson, PhD student Characterization • Prof. Mikael Lindgren, NTNU, Norway • Dr Jonas Örtegren, Post Doc • Eirik Glimsdal, Dipl. Stud • Dr. Anders Eriksson, FOI, Sweden • Dr. Cesar Lopes, FOI, Sweden Optical Equipment design • Dr. Henrik Ludwigs, Saab Tech AB

  11. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Project Goals Design and preparation of solid-state materials, with ability to clamp the transmitted energy ≤1 J @ 60% photopic transmission, for protection of eyes, E/O sensors and NVG against µs – ps pulses. • Preparation • Dendrimers • Nanohybrid materials • Solid-state glass materials • Characterization • Transmission • OPL - Clamping • Mechanisms • Modeling • The matrix - influence • Concentration • New nanomaterials

  12. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Solid-state optical limiting materials -Hybrid nanocomposites- • Enhanced chemical, physical and mechanical long term stability • Enhanced performance • Environmentally friendly composition • Shape processability Preparation Glass material Synthesis: Precursor Dendrimer ligand Synthesis: Precursor Me-organic compound Synthesis: Precursor Nanohybrid material Solid-state material Hybrid material Organic matrix Solid-state material Hybrid material Inorganic matrix

  13. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Preparation of solid materials • Glass materials • Nanohybrid precursors • Class I and II materials • Dendrimers • Coating • Preparation of solids, organic matrix

  14. Sensor Protection Stable upon hydrolysis OR OR NLO function Si Hydrolysable groups OR Swedish Defence Nanotechnology Program 2004-11-17 Class II nanohybrid materials + Si(OR)4 + H2O Class II solid-state material

  15. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Optical characterization • Spectroscopy • Optical absorption (UV-VIS and excited state absorption) • Steady state and time-resolved luminescense spectroscopy • OPL characterization (standard f/5 set-up)

  16. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Sample preparation Precision saw machine (Isomet 1000) and polishing machine (Logitech PM2)

  17. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Results year 1 Pt-Thiacalixarenes 50 mM och 12.5 mM

  18. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Results year 1 Synthesis and characterization of new NLO chromophores Dendrimer capped Pt-aryl-ethynyls – preliminary OPL:

  19. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Results year 1 Preparation of solid OPL materials : sol-gel PtG2 Boltorn H30

  20. Sensor Protection Swedish Defence Nanotechnology Program 2004-11-17 Scientific output2003 - 2004 • ~ 25 publications • P. Norman and H. Ågren ”First principles quantum modeling of optical power limiting” J. Comp. Theoretical Nanoscience, 2004 (in press) • R. Vestberg, A. Nyström, M. Lindgren, E. Malmström and A. Hult ”Encapsulation of porphyrin cores by bis-MPA dendrons” Chemistry of Materials 16, (2004), 2794 • P. Cronstrand, P. Norman, Y. Luo and H. Ågren ”Few states models for three-photon absorption” J. Chem. Phys. 121, (2004), 2020 • R. Vestberg, C. Nilsson, C. Lopes, B. Eliasson and E. Malmström ”Thiophene cored bis-MPA dendrimers for OPL applications” Journal of Polymer Science Part A: Polymer Chemistry (2004) • R. Vestberg, A. Eriksson, C. Lopes, M. Lindgren and E. Malmström ”Novel dendrimer-capped Pt-acetylides for OPL” SPIE 5621, 2004

  21. Porphyrin-cored 2,2-bis(methyole)propionic acid dendrimers 2,2-bis(methylol)propionic acid (bis-MPA) dendrimers have been obtainedby the direct addition of bis-MPA dendrons to free-base and Zn-porphyrins. The growth of dendrimers in the case of Zn-TPP = tetrakis(4-hydroxyphenyl)-porphine = is shown here.

  22. Fluorescence of dendrimers in THF No difference in emission for different generations of free base. For Zn-cored porphyrins the shoulder at 650 nm increases with increasing generation. Zn-TPP in Gx dendrimers Free-base TPP in G3

  23. We have compared dendrimer spectra with FBP and ZnP emission spectra in different solvents and solid matrices and also with IR and Raman spectra (nonresonance and normalRaman). Comparative theoretical study of all these spectra, including simple models of dendrimers (Zn-TPP) at different levels (DFT and AM1)permits us the following explanations

  24. Thisvibration is observed in Raman spectra at 1609 cm-1and is identified with 1614 cm-1vibronic 0-1 band in fluorescence (n10 of ag type). It is seen as a shoulder at 720 nm for free-base-TPP fluorescence in G3 dendrimer. It is shifted in TPP to lower frequency. The band is induced by large FC factor. No Herzberg-Teller contribution (ag)

  25. In Zn-TPP molecule this mode is mixed with the phenyl stretchings.Phenyl rings are out-of-porphpyrin-plane. When they bear bulky dendric MPA-substitutients this strongly influenceselectronic cloud ofthe Zn-porphpyrin chromophore The Herzberg-Teller mechanism now contributes more to intensity of vibronic line. It influence mixing of the S1(Qx)and the Soret states. Vibronic shoulder at 660 nm in ZnTPP fluorescence; its intensity increases with dendrimer generation. It is induced by Herzberg-Teller effect In Zn-P molecule this band is changed in comparison with FBP, since it includes nowZn-N vibrations (asymmetric wagging movement). This is b2g mode which includes also Ca-Cm vibrations in methynebridges.

  26. Among other low-frequency vibronic bandsthere is the nu27 = 755cm-1,which also includes the vibrations in methynebridges and Zn movement. The similar Herzberg-Teller mechanism contributes to intensity of this vibronic line with growing dendric MPA-substitutients. It gives additional emission band (two-hump shoulder) in G5 fluorescence

  27. This is ullustrated by Zn-TPP vibrations calculated at AM1 level

  28. Phosphorescence of free-base porphin and Zn-porphyrin. The efficient inter-system crossing ofporphyrins, which maintain a high concentration oftriplet-excited molecules is used now in a wide variety of applications from photodynamic therapy to nonlinear optical devices. We have explained for the first time the low phosphorescence efficiency of porphyrins without heavy ions by DT DFT calculations. We have obtained a slow radiative rate constantof the lowest triplet state, 3B2u, of free-base porphinphosphorescence (about 10-3s-1), which is in agreement withexperimental estimations. Phosphorescence of free-base porphin is determined byemission from the most active Tz spin sublevel, where z-axiscoinsides with the N-H...H-N bonddirection. It is polarised perpendicular to the molecular plane. Such a slow radiative decay is very unusualfor a molecule wich possesses lone pairs of electrons at nitrogen atomsand a number of excited np* states in the near UV region. It is explained by destructive interference of S-S and T-T contribution.

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