1. CALIFORNIA INSTITUTE OF TECHNOLOGY TIME DOMAIN TERAHERTZ SPECTROSCOPY OF POLYCYCLIC AROMATIC HYDROCARBONS Brandon Carroll  Marco A. Allodi  Sergio Ioppolo  Ian A. Finneran  Brett A. McGuire  Xander de Vries  Geoffrey A. Blake

2. Polycyclic Aromatic Hydrocarbons (PAHs) Nearly any combination of aromatic rings Stable with a wide variety of charge states, electronic states, and hydrogenation Highly photostable and functionalizable INTRODUCTION

3. Bands at 3.3 μ m 6- 9 μ m and 11-15 μ m consistently appear together, however their relative intensities vary widely Transitions due to sp 2 hybridized (aromatic) carbonaceous species No one species can explain the observed variations in intensity or line shape/width UIRS

4. FAR INFRARED PAH EMISSION Boersma et al. ApJ 729 64, (2011)

5. SPECTRAL COVERAGE

6. EXPERIMENTAL SETUP

7. ANTHRACENE PELLETS

8. Three simple PAHs Crystalline samples Polyethylene substrate 0.3 THz – 8 THz Multiple temperatures –10 K, 37.5 K, 75 K, 150 K, 300K SPECTRA

9. NAPHTHALENE 4.9 THz

10. NAPHTHALENE 5.2 THz

11. NAPHTHALENE Frequency (cm -1 ) 267 200133 67 0

12. NAPHTHALENE Frequency (cm -1 ) 267 200 67 0 Frequency (THz)

13. ANTHRACENE 2.5 THz

14. ANTHRACENE 3.3 THz

15. ANTHRACENE 7.0 THz

16. ANTHRACENE Frequency (cm -1 ) 267 200 67 0 Frequency (THz)

17. ANTHRACENE Frequency (cm -1 ) 267 200 67 0 Frequency (THz)

18. PYRENE 2.7 THz

19. PYRENE 5.7 THz

20. PYRENE Frequency (cm -1 ) 267 200 67 0 Frequency (THz)

21. PYRENE Frequency (cm -1 ) 267 200 67 0 Frequency (THz)

22. CONCLUSION AND FUTURE DIRECTIONS Initial spectra a promising Crystalline samples are promising, but complex Simple ab initio is a good start, but not complete

23. Si substrate Optical constants Lattice vibrations Additional species Matrix isolation CONCLUSION AND FUTURE DIRECTIONS Initial spectra a promising Crystalline samples are promising, but complex Simple ab initio is a good start, but not complete

24. ACKNOWLEDGEMENTS Blake Lab: -Jacob Good - Nate Crockett -Masha Klescheva -Coco Zhang -Dana Anderson -Katherine Kaufman -Alex Lockwood