1. Spectroscopic Line Shapes Of Broad Band Sum Frequency Generation Himali Jayathilake Igor Stiopkin, Champika Weeraman, Achani Yatawara and Alexander Benderskii Department of Chemistry, Wayne State University Detroit, MI

2. Interfacial Studies Biological Processes Biological Processes Molecular Electronics Molecular Electronics Nanotechnology Nanotechnology Molecular Organization at the Surface Function Surface Selective Spectroscopy Nature Living Organisms (Cell membrane) Industry (LCD Displays)

3. Outline Spectroscopic Spectroscopic Line Shapes Line Shapes 1. Amplitude 2. Line Width 3. Transition frequency Information extracted from Line shapes 1.Molecular organization i. Orientation ii. Conformational order iii. Packing 2. Molecular Dynamics Frequency Amplitude Spectroscopic Signal

4. Polarization Second Order Non- linear Susceptibility Surface-Selective Non-Linear Optical Spectroscopy  Surface selectivity:  (2) = 0 in isotropic media (bulk)

5. Vibrational Sum Frequency Generation (SFG) Broad-Band Vibrational SFG (Broad-band IR pulse + Spectrally narrow vis pulse) |v=0  |v=1 vis  vis IR  IR  SFG =  IR +  vis SFG vis IR SFG van der Ham, Vrehen, Eliel Opt. Lett. 21, 1448 (1996) Richter; Petralli-Mallow; Stephenson, Opt. Lett. 23, 1594 (1998)

6. Experimental Set-up PumpLasers Amplifier OPAOscillator1 2 SFG Monochromator CCD IR vis Sample SFG Spectrum IR output: 3-8  m 65-75 fs 300 cm -1 bandwidth 1-2  J/pulse 800 nm 40 nm bandwidth 803 nm 26 nm bandwidth 40 fs 2 mJ/pulse, 1 kHz Shaped vis pulse i. Stretcher ii. Etalon

7. Etalon OPA To the sample Grating Tunable slit Stretcher and Etalon

8. Spectroscopic Line Shapes in SFG Peaks are asymmetric-interference of the resonant and the nonresonant SFG Peaks are broad-convolution of the molecular response with the visible up-converted pulse Propiolic acid At air- water interface

9. How Time Delay Affects SFG Spectra? (-) ve Time Delay(+) ve Time Delay

10. 1. Stretcher Based Visible Pulses Vis. Width=17 cm -1 Vis. Width=37 cm -1 Electric field of time domain visible pulse

11. SFG Spectra From Stretcher Based Visible Vis. Width=17 cm -1 Vis. Width=37 cm -1

12. Fitting Procedure Time domain Molecular response function The 1 st order polarization The 2 nd order polarization Frequency domain 2 nd order susceptibility The BB-SFG Spectrum Fourier Transform FFT

13. 2Г2ГAnalysis  Peak Intensity get maximized at negative maximized at negative time delays time delays  FWHM get minimized at negative time delays negative time delays

14. 2. Etalon Based Visible Pulse Electric field of time domain visible pulse

15. SFG Spectra From Etalon Based Visible

16. Fitting Results

17. Summary  Visible pulse shape and time delay can be used toenhance the SFG signal intensity and obtain the desired line shape without sacrificing the spectral resolution  Visible pulse shape and time delay can be used to enhance the SFG signal intensity and obtain the desired line shape without sacrificing the spectral resolution  Combining theoretical modeling with experimental measurements  Combining theoretical modeling with experimental measurements, i. information such as true line width can be extracted ii. observed line shapes can be described

18. Acknowledgements The Group Adib J. Samin Funding Wayne State University ACS-PRF NSF http://chem.wayne.edu/benderskii-group/

19. Modeled homodyne detected SFG spectrum Asymmetric homodyne detected SFG spectrum Symmetric real part of the resonant contribution Asymmetric imaginary part of the resonant contribution Non-resonant contribution

20. Visible Pulse Shape From Stretcher The inset shows the front view of the grating

21. Etalon OPA To the sample Grating Tunable slit Stretcher and Etalon