1. 1 STRUCTURE OF COLD, MIXED PARA-H 2 /D 2 CLUSTERS Russell Sliter & Andrey Vilesov University of Southern California Department of Chemistry OSU International Symposium on Molecular Spectroscopy June 25, 2010 FB02

2. 2 He vs. H 2 Superfluid Metastable superfluid phase Ginzburg, Sobianin, JETP Letters 15 (1972) 343 Apenko, Phys. Rev.B 60 (1999) 3052 4 HeH2H2 BosonI = 0I = 0, 1 MassM = 4 auM = 2 au *Interactionε m = 11 Kε m = 34 K *Binding interaction in dimers

3. 3 Previous Work Growth of large pH 2 clusters in a seeded nozzle beam expansion D = 1 mm Cooling and cluster growth T 0 = 15-30 K P 0 = 20 atm X% pH 2 in He Kuyanov-Prozument, Kirill; Vilesov Andrey F. Physical Review Letters, 101, 205301, (2008). Supercooling bulk samples proven unsuccessful Clusters allow lower freezing point due to size effects Expansion w/ He allows cooling down to 0.37 K Average Cluster Size: ~ 5*10 4

4. 4 T ≈ 1.2 K T ≈ 10 K T ≈ 2 K 10% pH 2 in He 1% pH 2 in He 0.5% pH 2 in He Free pH 2 Rotational S 0 (0) line of pH 2 clusters in He ( = 0  0, J = 2  0 ) J = 2 J = 0 Rotational CARS Splitting pattern depends on crystal structure J = 2m j = ±2, ±1, 0 Splitting in hcp crystal Kuyanov-Prozument, Kirill; Vilesov Andrey F. Physical Review Letters, 101, 205301, (2008).

5. 5 Phase Separation in 3 He/ 4 He Mixtures T c = 0.87 K X c ( 3 He) = 0.67 D. O. Edwards and M. S. Pettersen, J. Low. Temp. Phys. 87, 473 (1992) ( 3 He)

6. 6 () Experimental CARS Setup Continued PMT L Grating Filters nozzle T 0 = 15-30 K P 0 = 20 atm X% (pH 2 + D 2 ) in He k1k1 k1k1 k2k2 k3k3

7. 7 Vibrational CARS of pH 2 in pH 2 /He Clusters T = 20 K

8. 8 Vibrational CARS of pH 2 in pH 2 /D 2 /He Clusters X = 1% (H 2 + D 2 ) in HeX = 8% (H 2 + D 2 ) in He 58% D 2 27% D 2 0% D 2 85% D 2 37% D 2 0% D 2

9. 9 Vibrational CARS of pH 2 in pH 2 /D 2 Liquid Expansion (X = 100%)

10. 10 Vibrational CARS in pH 2 /D 2 Clusters

11. 11 In gasIn solid ν = 0 Q 1 (0) Band due to vibron propagation Δν I = 8.7 cm -1 Δν B = 2.7 cm -1 Δk = 0 Vibron Hopping &Vibrational shift in solid pH 2 R ν = 1 J. van Kranendonk, Solid hydrogen. Theory of the properties of solid H 2, HD and D 2. (1983)

12. 12 Vibron Hopping in pH 2 /D 2 Clusters pH 2 D2D2 D2D2 D2D2 D2D2 D2D2 D2D2 D2D2 2.7 cm -1 0

13. 13 Vibrational CARS of pH 2 in pH 2 /D 2 Clusters Bulk Mixture

14. 14 Phase Separation in pH 2 /D 2 Clusters Randomly mixed Clusters Phase separated Clusters D2D2 pH 2

15. 15 Model of Phase Separation in pH 2 /D 2 Liquids M. Lambert, Phys. Rev. Lett. 4, 555 (1960) No phase separation in bulk liquid pH 2 /D 2 mixtures Mixing stability based on lowering free energy G = H – T·S High Temperature Entropy dominates

16. 16 Phase Separation in pH 2 /D 2 Liquids Modeling of phase separation

17. 17 Conclusions pH 2 /D 2 solid cluster frequency shifts follow expectations observed in bulk mixed hydrogen samples pH 2 /D 2 liquid cluster vibrational Raman frequency shift saturates with increasing D 2 Phase separation observed Estimation of phase separation of ~ 3 K helps validate supercooled liquid clusters previously observed

18. 18 Acknowledgments Melody Sun Evginy Loginov Luis Gomez Andrey Vilesov $upport