1. HIGH-RESOLUTION COHERENT THREE-DIMENSIONAL SPECTROSCOPY OF IODINE
Zuri House, Peter C. Chen, Thresa A. Wells
Spelman College, Atlanta GA
Benjamin R. Strangfeld
Georgia Institute of Technology, Atlanta GA

2. Outline/Purpose Background Experimental Set- up
Four Wave Mixing Processes
Data Analysis
Next Step
Conclusion
Acknowledgement s
Purpose of Experiment: To explore and test a new 3 dimensional technique on Iodine

3. Background- Iodine Purpose of the study
Understand how 3D spectroscopy can be used for molecules without known spectroscopic constants
Establish a standard procedure for analyzing unknown molecules
Reasons for choosing iodine
Energy levels for two states involved are known and thoroughly studied (X to B transition)
Simple diatomic molecule with no isotopomers
Used low resolution absorption spectrum to determine roughly where to set laser

4. Electronic Spectra

5. Background Types of Spectroscopic Methods
Raman, IR, UV-Vis, NMR (a few examples)
Characteristics of Techniques (in heavily congested systems)
1D- highly congested 2D- less congested
3D- even less congested, and selective (see next slide)
*2D and especially 3D techniques are new and innovative I λb λa λa

6. Data Analysis- Original Run

7. Resonance 3D spectroscopy is a fully resonant process
When 3 beams are resonant with the levels in the molecule, a lot of light is generated and the peaks are more intense
triply resonant features are more intense than > doubly > Singly

8. Four Wave Mixing Process
532 M S ω4
M 532 S ω4
M S 532 ω4
532 S M ω4
i ii iii iv
ω4= ω532- ωS + ωM
Non-linear optical process
Can only be done with very intense (pulsed) lasers
Taking 3 beams and overlapping them to create a new 4th beam that has its own wavelength (determined by molecule present)
Detected by monochromator
Which process is responsible for my results?

9. Experimental Set-up 3 lasers used for the Four Wave Mixing Process
532nm Nd: YAG Laser (GCR)
Raman Shifters
SOPO
Sample
532nm Nd: YAG Laser
532 S M ω4
532nm Nd: YAG Laser (GCR)
MOPO
Monochromator with CCD
Just like in the 2D GC example, we have more than one variable device responsible for more than one domain (in this case, two frequencies).
3 lasers used for the Four Wave Mixing Process
Mopo (tunable)
Sopo (broadband OPO)
Can adjust to find fully resonant peaks
532nm ND: YAG laser
Wavelength cannot be changed
Selects J value, primarily vibrational changes

10. Process 4 Diagram B state, high v’ B state, low v’ X state, high v”
X state, low v”

11. Data Analysis- Original Run

12. Slope of the line ω4 – (ω532 – ωS) = ωM ωM = ω4 + (ωS – ω532)
Slope of lines
The slope of the line which passes through all of the clusters in that particular area in the pattern was derived
Slope should be 1 because the axes are ω4 vs. ωM
Derivation from equation ω4 = ω532- ωS + ωM to y=mx+b
ω4 – (ω532 – ωS) = ωM
ωM = ω (ωS – ω532)
y = mx b
Used to help determine spectroscopic constants

13. Vertical Spacing Intercluster Relationship
Indicates spacing between the excited levels within the B-state
Since levels are relatively evenly spaced, levels are not approaching the dissociation limit for the B-state

14. Diagonal Spacing Intercluster Relationship
Tells us about the spacing between the excited levels within the higher X-state
Aren’t converging, so dissociation level hasn’t been reached
All of this information determined is electronic and vibrational
Next: find rotational information (intracluster relationship)

15. Intracluster relationship

16. Further Study Use simulation (via Excel spreadsheet) to:
Tune the laser to a specific resonance and decrease the bandwidth to control the number of peaks within a cluster
Employ same techniques Benjamin Strangfeld described and calculate B’s for designated triangles within a cluster
Compare coherent 3D spectroscopic constant to literature values

17. Acknowledgements
Peter Chen Thresa Wells Benjamin Strangfeld Aspiring Researchers Program NSF Grant: NSF CHE