1 / 48

Darin J. Ulness, Concordia College

1. Darin J. Ulness, Concordia College. Noisy Light Spectroscopy. Noisy Light Spectroscopy: Putting noise to good use. Darin J. Ulness Department of Chemistry Concordia College Moorhead, MN. A. The. 2. Darin J. Ulness, Concordia College. Noisy Light Spectroscopy. Outline.

abril
Download Presentation

Darin J. Ulness, Concordia College

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 1 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Noisy Light Spectroscopy: Putting noise to good use Darin J. Ulness Department of Chemistry Concordia College Moorhead, MN A The

  2. 2 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Outline • Introduction • II. Experiment • Coherent Raman Scattering • III. Hydrogen Bonding • Pyridine systems • IV. Prospectus

  3. 3 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Spectroscopy Using light to gain information about matter Information Uses of information • In Chemistry • In Biology • In Engineering • Transition frequencies • Lineshapes • Susceptibilities

  4. 4 Spectrum One frequency (or color) frequency time Darin J. Ulness, Concordia College Noisy Light Spectroscopy Light • Electromagnetic radiation • Focus on electric field part

  5. 5 Time resolution on the order of the correlation time, tc Noisy Light Spectrum Frequency Darin J. Ulness, Concordia College Noisy Light Spectroscopy Noisy Light: Definition • Broadband • Phase incoherent • Quasi continuous wave

  6. 6 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Experiment • Coherent Raman Scattering: e.g., CARS • Frequency resolved signals • Spectrograms • Molecular liquids

  7. 7 Material Signal Light field P(t) = P(1) + P(2) + P(3) … P(1) = c(1)E, P(2) = c(2)EE, P(3) = c(3)EEE Darin J. Ulness, Concordia College Noisy Light Spectroscopy Nonlinear Optics P= c E Perturbation series approximation

  8. 8 Darin J. Ulness, Concordia College Noisy Light Spectroscopy CARS Coherent Anti-Stokes Raman Scattering wCARS w1 w1-w2= wR wCARS= w1 +wR w2 w1 wR

  9. 9 Darin J. Ulness, Concordia College Noisy Light Spectroscopy CARS with Noisy Light • I(2)CARS • We need twin noisy beams B and B’. • We also need a narrowband beam, M. • The frequency of B (B’) and M differ by roughly the Raman frequency of the sample. • The I(2)CARS signal has a frequency that is anti-Stokes shifted from that of the noisy beams. I(2)CARS B’ M B

  10. 10 Computer CCD Interferometer Monochromator t Sample B’ B I(2)CARS M Lens Broadband Source (noisy light) Narrowband Source Darin J. Ulness, Concordia College Noisy Light Spectroscopy I(2)CARS: Experiment

  11. 11 Darin J. Ulness, Concordia College Noisy Light Spectroscopy I(2)CARS: Spectrogram Computer CCD Interferometer Monochromator t Sample B’ B I(2)CARS M Lens Broadband Source Narrowband Source • Signal is dispersed onto the CCD • Entire Spectrum is taken at each delay • 2D data set: the Spectrogram

  12. 12 A Pixel A Pixel B B C Pixel C Darin J. Ulness, Concordia College Noisy Light Spectroscopy I(2)CARS: Spectrogram Oscillations: downconversion of Raman frequency. Decay: Lineshape function Dark regions: high intensity Light regions: low intensity

  13. 13 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Spectrogram No new information can be extracted. However… • Huge oversampling gives much enhanced precision. • Visually appealing presentation of data gives much insight.

  14. 14 Fourier Transformation X-Marginal Darin J. Ulness, Concordia College Noisy Light Spectroscopy I(2)CARS: Data Processing

  15. 15 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Virtues of I(2)CARS • Less expensive. • Easier experiment to perform. • Signals are more robust. • Immune to dispersion effects. • Exquisitely sensitive to relative changes in the vibrational frequency and dephasing rate constant.

  16. 16 H O, N O, N Darin J. Ulness, Concordia College Noisy Light Spectroscopy Hydrogen Bonding • Interaction between a hydrogen atom and oxygen or nitrogen (or fluorine) • A very weak chemical interaction (bond) • A very strong physical interaction • Exploited extensively in biological systems

  17. 17 N H H C C C C H H C H Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine Systems • Why Pyridine • Simple molecule • Important component in many compounds • Biological importance • Strong I(2)CARS signal • H-bond acceptor but not a H-bond donor.

  18. 18 A1 1 990 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine: Normal Modes Ring Breathing A1 Triangle 12 1030

  19. 19 • Neat Pyridine • Two peaks • With H-bond • Three peaks Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine and H-bonding

  20. 20 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine and H-bonding • Key Results • Some pyridine is free some is hydrogen bonded • Hydrogen bonding blue-shifts the ring breathing mode • Hydrogen bonding does not shift the triangle mode

  21. 21 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine: Inner Tube Model • Molecular orbitals • Electrostatics • Compare with benzene • Stabilization through p delocalization • H-bonding makes pyridine more “benzene-like”

  22. 22 ≈ Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine: Inner Tube Model Electron density for Benzene Electron density for free pyridine + = p e- density Full e- density sp2 e- density Electron density for H-bonded pyridine + = p e- density Full e- density sp2 e- density

  23. 23 3.0 2.8 Formamide 2.6 2.4 4 cm-1 2.2 2.0 1.8 1.6 NormalizedX marginal intensity Water 1.4 8 cm-1 1.2 1.0 0.8 14 cm-1 Acetic Acid 0.6 0.4 0.2 0.0 980 990 1000 1010 1020 1030 1040 -1 Raman wavenumber / cm Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine: Test of Model Vary the strength of hydrogen bonding Formamide N-H-N bond ~ 3-4 Kcal/mol Water N-H-O bond ~ 6-7 Kcal/mol Acetic Acid Proton transfer (acid/base)

  24. 24 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine: Peak Broadening

  25. 25 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Peak Broadening Models Network model Etc. Thermalized distribution model Fileti, E.E.; Countinho, K.; Malaspina, T.; Canuto, S. Phys. Rev. E. 2003, 67, 061504.

  26. 26 3.0 2.7 2.4 O T = 60 C 2.1 1.8 O T = 40 C Normalized X marginal intensity 1.5 O T = 20 C 1.2 O T = 0 C 0.9 0.6 O T = -20 C 0.3 O T = -40 C 0.0 980 990 1000 1010 1020 1030 1040 -1 Raman wavenumber / cm Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine/water Temperature Xpy = 0.55

  27. 27 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine/water Temperature Xpy = 0.55 3.5 Hydrogen Bonded Ring Breathing Mode -1 3.0 Peak width (obs) / cm Triangle Mode 2.5 2.0 1.5 “Free” Pyridine Ring Breathing Mode 1.0 -40 -20 0 20 40 60 O Temperature / C

  28. 28 Triangle Mode 1031.5 1031.0 1030.5 1030.0 Hydrogen Bonded Ring Breathing Mode 1029.5 998 Raman Wavenumber / cm 996 994 “Free” Pyridine Ring Breathing Mode 992 990 988 -40 -20 0 20 40 60 O Temperature / C Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine/water Temperature Xpy = 0.55 -1

  29. 29 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Prospectus • Summary: • Noisy light provides an alternative method for probing ultrafast dynamics of the condensed phase. • Useful tool for probing hydrogen bonding using “test” molecules. • Simple model useful in understanding hydrogen bonding in pyridine. • Thermalized distribution is likely cause of peak broadening.

  30. 30 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Prospectus • Future of noisy light at Concordia: • Other pyridine based molecules • Hydroxymethyl pyridine. • Halo pyridines. • Other nitrogen heterocycles. • A principle goal is to develop an I(2)CARS based microscopy.

  31. 31 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Acknowledgements Former Students Jahan Dawlaty: Cornell University, Ph.D. candidate in optical electronics Dan Biebighauser: Vanderbilt University, Ph.D. in mathematics John Gregiore: Cornell University, Ph.D. candidate in physics Duffy Turner: MIT, Ph.D. candidate in physical chemistry Pye Phyo Aung: John’s Hopkins University, Ph.D. candidate in mathematics Tanner Schulz: University of Minnesota, Ph.D. candidate in physics Lindsay Weisel: Michigan State University, Ph.D. candidate in physical chemistry Other Group Members Current Students Britt Berger Zach Johnson Erik Berg Danny Green Sarah Freeman Dr. Mark Gealy, Department of Physics Dr. Eric Booth, Post-doctoral researcher Funding NSF CAREER Grant CHE-0341087 Henry Dreyfus Teacher/Scholar program Concordia Chemistry Research Fund

  32. Darin J. Ulness, Concordia College Noisy Light Spectroscopy

  33. 23 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Pyridine and Water

  34. 7 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Noisy Light: Alternative • Its cw nature allows precise measurement of transition frequencies. • Its ultrashort noise correlation time offers femtosecond scale time resolution. • It offers a different way to study the lineshaping function. • It is particularly useful for coherent Raman scattering. • Other spectroscopies: photon echo, OKE, FROG, polarization beats…

  35. 8 Noisy Light Spectroscopy Optical coherence theory Perturbation theory: Density operator Darin J. Ulness, Concordia College Noisy Light Spectroscopy Theory

  36. 9 Difficulty • The cw nature requires all field action permutations. The light is always on. • The proper treatment of the noise cross-correlates chromophores. Solution • Factorized time correlation (FTC) diagram analysis Darin J. Ulness, Concordia College Noisy Light Spectroscopy Theoretical Challenges • Complicated Mathematics • Complicated Physical Interpretation

  37. 10 Messy integration and algebra Construction Rules Evaluation Rules Set of intensity level terms (pre-evaluated) Set of FTC diagrams Set of evaluated intensity level terms easy Physics hard hard Darin J. Ulness, Concordia College Noisy Light Spectroscopy FTC Diagram Analysis

  38. A1 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Utility of FTC Diagrams • Organize lengthy calculations • Error checking • Identification of important terms • Immediate information of about features of spectrograms • Much physical insight that transcends the choice of mathematical model.

  39. A2 a P(t,{ti}) b P(s,{si}) Darin J. Ulness, Concordia College Noisy Light Spectroscopy Example: I(2)CARS • FTC analysis • Each diagram with arrows has a topologically equivalent partner diagram containing only lines: 2:1 dynamic range • Each diagram with arrows has a topologically equivalent partner diagram that has arrows pointing in the opposite direction: signal must be symmetric in t arrow segments: B, B’ correlation t-dependent line segments: B, B or B’,B’ correlation t-independent

  40. 4 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Modern Spectroscopy Frequency Domain Time Domain • Measure Spectra • Examples • IR, UV-VIS, Raman • Material response • Spectrally narrow • Temporally slow • Response to light pulse • Examples • PE, transient abs. • Material response • Spectrally broad • Temporally fast

  41. 4 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Modern Spectroscopy Frequency Domain Time Domain • Measure Spectra • Examples • IR, UV-VIS, Raman • Material response • Spectrally narrow • Temporally slow • Response to light pulse • Examples • PE, transient abs. • Material response • Spectrally broad • Temporally fast

  42. 4 Darin J. Ulness, Concordia College Noisy Light Spectroscopy Modern Spectroscopy Frequency Domain Time Domain • Measure Spectra • Examples • IR, UV-VIS, Raman • Material response • Spectrally narrow • Temporally slow • Response to light pulse • Examples • PE, transient abs. • Material response • Spectrally broad • Temporally fast Is there another useful technique? Noisy light? YES!

  43. A3 A Pixel A Pixel B B C Pixel C Darin J. Ulness, Concordia College Noisy Light Spectroscopy Example: I(2)CARS • The I(2)CARS data shows • 2:1 dynamics range • t symmetry

  44. A4 (a) 0.30 0.25 0.20 0.15 g s 0.10 0.05 0.00 0 1 2 3 4 5 S/N (b) 0.25 0.20 0.15 0 D w s 0.10 0.05 0.00 0 1 2 3 4 5 S/N Darin J. Ulness, Concordia College Noisy Light Spectroscopy

  45. A5 Darin J. Ulness, Concordia College Noisy Light Spectroscopy

  46. A6 Darin J. Ulness, Concordia College Noisy Light Spectroscopy

  47. A7 Darin J. Ulness, Concordia College Noisy Light Spectroscopy - ∆G° Product Favored - ∆H° Exothermic - ∆S° Entropically unfavorable

  48. A8 Darin J. Ulness, Concordia College Noisy Light Spectroscopy c(3)complex = Icomplexc(3)free xfree Icomplex = Ifree at 0.21 mole fraction c(3)complex = 1c(3)free .79 c(3)complex = 3.76c(3)free

More Related