Noisy Light Spectroscopy A science story Darin J. Ulness Department of Chemistry Concordia College, Moorhead, MN

Spectroscopy Using light to gain information about matter Spectra Transition frequencies Time dynamics Absorptivities Susceptibilities InformationUses of information In Chemistry In Biology In Engineering

Modern Spectroscopy Frequency Domain Measure Spectra Examples IR, UV-VIS, Raman Material response Spectrally narrow Temporally slow Time Domain Response to light pulse Examples PE, transient abs. Material response Spectrally broad Temporally fast

Modern Spectroscopy Frequency Domain Measure Spectra Examples IR, UV-VIS, Raman Material response Spectrally narrow Temporally slow Time Domain Response to light pulse Examples PE, transient abs. Material response Spectrally broad Temporally fast

Time Domain Spectroscopy Ultrashort pulses are used to excite a molecule

Time Domain Spectroscopy Ultrashort pulses are used to excite a molecule

Creating Ultrashort Pulses Fourier Transforms! Things that happen fast in time require a broad frequency spectrum To make a short pulse you need a lot of colors

Phase Locking Synchronize the phase of the electric field Many colors conspire to create a short pulse The phases of the different colors need to be “locked”

Noisy light Spectroscopy Unlock the phase! The phases of the different colors have a random relation to one another Many colors conspire to create a short pulse coherence time Noisy Light Spectrum Frequency

Noisy light Spectroscopy Interacting with molecules The noisy light is “always on” …it is quasi-continuous wave The field may interact with the molecule at any time

Foundations of Noisy Light Optical coherence theory Perturbation theory: Density operator Noisy Light Spectroscopy

Nonlinear Spectroscopy P=  E Signal Material Light field Perturbation series approximation P(t) = P (1) + P (2) + P (3) … P (1) =  (1) E, P (2) =  (2) EE, P (3) =  (3) EEE

CARS Coherent Anti-Stokes Raman Scattering  1 -  2 =  R  CARS =  1 +  R RR 11 11 22  CARS

Bichromophoric Model   Noisy light P(t)P(t) (3) P(s)P(s) (3) *

Theoretical Challenges Complicated Mathematics Complicated Physical Interpretation Difficulty The cw nature requires all field action permutations. The light is always on. The proper treatment of the noise cross-correlates chromophores.

New Viewpoint: The  (5) Story

Theoretical Challenges Complicated Mathematics Complicated Physical Interpretation Difficulty The cw nature requires all field action permutations. The light is always on. The proper treatment of the noise cross-correlates chromophores.

FTC Diagram Analysis Set of intensity level terms (pre-evaluated) Set of evaluated intensity level terms Messy integration and algebra Set of FTC diagrams Construction Rules Evaluation Rules Physics hard easy

FTC Diagram Analysis   P(t,{t i }) P(s,{s i }) arrow segments:  -dependent correlation line segments:  -independent correlation

I (2) CARS Monochromator Narrowband Source Broadband Source Lens Sample Interferometer t B B’ M I (2) CARS Computer CCD Signal is dispersed onto the CCD Entire Spectrum is taken at each delay 2D data set: the Spectrogram

I (2) CARS: Data Processing Fourier Transformation X-Marginal

I (2) CARS: Hydrogen Bonding FT Neat Pyridine Pyridine/ Water X w = 0.55

I (2) CARS: Hydrogen Bonding

I (2) CARS: Halogen Bonding

Halogen Bonding Electropositve  -hole Test Charge Electroneutral “ring” Electronegative “belt”

Photosynthesis

Acknowledgements Students Theory Jahan Dawlaty Dan Biebighauser John Gregiore Duffy Turner Kurt Haag Issac Heath Carena Daniels Other Group Members Dr. Mark Gealy, Department of Physics Dr. Eric Booth, Post-doctoral researcher Dr. Haiyan Fan, Post-doctoral researcher Funding NSF CAREER Grant CHE Henry Dreyfus Teacher/Scholar program Concordia Chemistry Research Fund Method Development Pye Phyo Aung Tanner Schulz Lindsay Weisel Krista Cosert Perrie Cole Alex Harsh Britt Berger Zach Johnson Thao Ta Hydrogen/Halogen bonding Eric Berg Jeff Eliason Diane Moliva Jason Olson Scott Flancher Danny Green Photosynthesis Becca Hendrickson Meghan Knudtzon Dylan Howie Bobby Spoja