1. Development of a Sheath-Flow Supercritical Fluid Expansion Source for Vaporization of Nonvolatiles at Moderate Temperatures Bradley M. Gibson and Jacob T. Stewart Department of Chemistry, University of Illinois at Urbana- Champaign Benjamin J. McCall Departments of Chemistry and Astronomy, University of Illinois at Urbana-Champaign

2. What is a supercritical fluid? Figure from:http://en.wikipedia.org/wiki/Supercritical_fluid {2}

3. Why use supercritical fluids? Figures from:B. Brumfield. Development of a quantum cascade laser based spectrometer for high-resolution spectroscopy of gas phase C 60. UIUC, 2011. {3} C 60 Vapor Pressure

4. Why use supercritical fluids? Figures from:B. Brumfield. Development of a quantum cascade laser based spectrometer for high-resolution spectroscopy of gas phase C 60. UIUC, 2011. {4}

5. Why use supercritical fluids? Figure from:B. E. Brumfield et al. Rev. Sci. Instrum. 81, 063102 (2010). {5}

6. Why use supercritical fluids? Figures from:J. T. Stewart. High-resolution infrared spectroscopy of large molecules and water clusters using quantum cascade lasers. UIUC, 2013. {6} Estimated: Observed: (NEA ~ 0.6 ppm)

7. Why use supercritical fluids? {7} Inefficient Vibrational Cooling Large partition function Poor density of states at low energy

8. How does the source work? {8}

9. How does the source work? {9}

10. How does the source work? {10}

11. How does the source work? {11}

12. What affects the final temperature? Extraction chamber temperature Pure CO 2 : > 305 K 7:3 CO 2 :toluene: ~ 450 K 96:4 CO 2 :naphthalene: ~ 340 K Nozzle temperature Aerosol-formation limited 7:3 CO 2 :toluene: ~ 400 K Argon backing pressure Expansion composition Velocity matching Figures adapted from:S. R. Goates, N. A. Zabriskie, J. K. Simmons, B. Khoobehi. Anal. Chem. 59, 2927 (1987) C. H. Sin, M. R. Linford, and S. R. Goates. Anal. Chem. 64, 233 (1992) {12}

13. How can we test the source? {13} Methylene Bromide Solubility unknown No signal observed Pyrene Solubility in pure CO 2 too low Solubility with cosolvents unknown No signal yet Visible pyrene output – mg/ hr scale D2OD2O Very strong monomer signals observed Poor for vibrational temperature estimates

14. Does the source cool efficiently? {14} D 2 O Tests 1 11 ←0 00 rovibrational transition Clear evidence of cooling (T rot < 16 K) Works from 400 - 500 K nozzle 350-370 K mixing chamber (limited by heater)

15. What molecules can we target? {15} Nonvolatile Molecules Fullerenes Polycyclic aromatics Perylene Coronene

16. What are the source’s limitations? {16} Fundamental Limitations Low vapor production rate Minimum “starting” temperature Appropriate solvent system required Design-Specific Limitations Clogging / multi-phase behavior Limited temperature range (<370 K) Limited pressure range (<3600 psi)

17. Conclusions {17} Should allow vaporization at moderate temperatures Prototype source completed Tests with D 2 O appear promising Numerous interesting targets available Design improvements and additional testing underway

18. Acknowledgements {18} McCall Group Claire Gmachl Steven Goates