Prof. Robert P. Lucht School of Mechanical Engineering, Purdue University, W. Lafayette, IN

1. Selective, Sensitive Detection of Dipicolinic Acid and Other Molecules (NO, C6H6, C2H2) Using CARS Techniques Prof. Robert P. Lucht School of Mechanical Engineering, Purdue University, W. Lafayette, IN Institute for Quantum Studies, Texas A&M University, College Station, TX 2003 TAMU/DARPA/ONR Workshop on Quantum Optics, Jackson Hole, WY, July 7-11, 2003

2. Acknowledgments • Funding Support from DARPA, DOE Office of Basic Energy Sciences, ARO • Experiments: Sherif Hanna, Waruna Kulatilaka, Jonathan DuBois (Texas A&M MEEN graduate students), Dr. Zane Arp (now at Los Alamos) • Modeling: Joel Kuehner (Univ. Illinois) • Prof. Marlan Scully (Physics), Dr. Tomas Opatrny (Physics),Prof. Phil Hemmer (EE)

3. Outline of the Presentation • Introduction and Motivation • Laser Diagnostics in Combustion: Dual-Pump CARS • Electronic-Resonance-Enhanced CARS of NO: Experiments and Modeling • Electronic Resonance CARS of C2H2 • CARS Detection of Solid DPA • Conclusions and Future Work

4. CARS Experiments in Flames Triple-pump CARS measurements performed in laminar hydrogen/air diffusion flame. Simultaneous acquisition of single-shot H2/N2 and H2/O2 spectra demonstrated.

5. Dual-Pump CO2/N2 CARS Performed in Exhaust of JP8-Fueled Combustor at WPAFB

6. Dual-Pump CARS of N2/CO2

7. Dual-Pump CARS Spectrum of N2/CO2 from Hencken Burner N2 CO2 CO2

8. Anthrax Spore Detection • Weaponized anthrax mailed to Senate offices, National Enquirer offices Fall 2001 • Anthrax difficult to detect in short period of time • Anthrax spores can remain dangerous for years • Anthrax diagnosis must be rapid to prevent severe damage or death

9. Ultraviolet Resonant Raman Spectra 3b: Calcium Dipicolinate 2b: Bacillus Cereus 1b: Bacillus Megaterium

10. Research Roadmap “Ordinary” CARS ERE CARS NO CARS Gas Phase Benzene CARS Liquid, 992 cm-1 C2H2 CARS Gas Phase DPA CARS Powder Polycrystalline 998 cm-1 DPA, Benzene CARS DPA in Spores

11. Electronic-Resonance-Enhanced Coherent Anti-Stokes Raman Scattering (ERE CARS) • ERE CARS was explored as a combustion diagnostic technique by Taran, Attal-Tretout and co-workers from the late 1970s to early 1990s • Technique was complicated both experimentally and theoretically because only two laser frequencies were used, both electronically resonant • Our ERE CARS approach is a variant on the dual-pump CARS technique, demonstrated on NO in gas cell to gain understanding of the physics

12. ER CARS, Pump 1 = Pump 2 Druet and Taran Prog Quant Elec 1979

13. Electronic Resonance CARS of NO

14. Electronic Resonance CARS Detection of NO

15. ERCARS Beam Geometry

16. Stokes Scan, Fixed Pump 2

17. NO CARS Spectrum: Theory

18. CARS Detection of NO

19. Electronic Resonance CARS Detection of NO

20. Electronic Resonance CARS Detection of NO

21. Polarization Suppression of Nonresonant Background

22. NO Electronic Resonance CARS with Background Suppression

23. Stokes Scan, Comparison of Theory and Experiment

24. Pump 2 Scan, Fixed Stokes

25. UV Pump Scan, Comparison of Theory and Experiment

26. Energy Level Diagram

27. CARS SusceptibilityNear Electronic Resonance Raman resonance Resonance enhancement “Normal” Raman cross section

28. Detailed Energy Level Diagram

29. Acetylene ERE CARS Spectrum

30. Theoretical Acetylene CARS Spectrum

31. Acetylene Electronic Spectrum Watson et al., J. Mol. Spectrosc. 95, 101 (1982)

32. DPA, Benzene CARS System

33. DPA, Benzene CARS Spectra

34. Conclusions • NO detected by electronic resonance CARS, spectrum observed clearly for 100 ppm NO • Sensitive, selective detection of minority species demonstrated, good agreement between model and experiment • ERE CARS of C2H2 demonstrated, significant resonant enhancement observed • Very strong CARS signal from DPA demonstrated, narrow spectral feature at 998 cm-1 observed

35. Research Roadmap “Ordinary” CARS ERE CARS NO CARS Gas Phase Benzene CARS Liquid, 992 cm-1 C2H2 CARS Gas Phase DPA CARS Powder Polycrystalline 998 cm-1 DPA, Benzene CARS DPA in Spores

36. Future Work • Experimental measurements of dissolved DPA and/or solid DPA particles and benzene by ERE CARS • Study two different ERE CARS schemes for DPA: (w1, w2 visible, w3 ultraviolet) or (w1, w2 ultraviolet, w3 = w1) • Work towards ERE CARS microscopy, focus UV beam(s) to less than 10 microns

37. ERE CARS of DPA

38. ERE CARS of DPA

39. Multi-Pump CARS Measurements in Combustion Systems • Electronic resonance CARS technique demonstrated in this work is a variant of the technique of dual-pump CARS • Dual-pump CARS developed for simultaneous measurement of two species in flames

40. Electronic Resonance Enhancement Factor l0 = 532 nm

41. Electronic Resonance Enhancement Factor – Saturated w3

42. Theoretical Acetylene CARS Spectrum

43. Single-Shot Dual-Pump CO2/N2 CARS Spectrum from JP8-Fueled Combustor

44. Third-order Perturbation TheoryResult for CARS Susceptibility

45. NO Electronic Resonance CARS with Background Suppression

46. Third-order CARS SusceptibilityNear Electronic Resonance ~0 ~0

47. ER CARS, Pump 1 = Pump 2 Doerk et al. Appl Phys B 1997

48. Pump 2 Scan, Comparison of Theory and Experiment

49. NO Electronic Spectroscopy J = N + S

50. NO Electronic Spectroscopy J = N - S