Observation of crystallization slowdown in supercooled para-hydrogen and ortho-deuterium quantum liquid mixtures

We report a quantitative experimental study of the crystallization kinetics of supercooled quantum liquid mixtures of para-hydrogen (pH$_2$) and ortho-deuterium (oD$_2$) by high spatial resolution Raman spectroscopy of liquid microjets. We show that in a wide range of compositions the crystallization rate of the isotopic mixtures is significantly reduced with respect to that of the pure substances. To clarify this behavior we have performed path-integral simulations of the non-equilibrium pH$_2$-oD$_2$ liquid mixtures, revealing that differences in quantum delocalization between the two isotopic species translate into different effective particle sizes. Our results provide first experimental evidence for crystallization slowdown of quantum origin, offering a benchmark for theoretical studies of quantum behavior in supercooled liquids.Comment: 6 pages, 3 figure

Experiments on microjets of undercooled liquid hydrogen

28th International Symposium on Rarefied Gas Dynamics 2012 (2012). AIP Conf. Proc.; 9 pags. ; 7 figs. ; 1 tab. ; PACS: 67.63.Cd, 33.20.Fb, 64.60.My, 64.70.dg, 47.60.KzNovel experiments on liquid microjets (filaments) of hydrogen and deuterium, carried out at the Laboratory of Molecular Fluid Dynamics of the IEM, are reported. These filaments, less than 10 microns in diameter, are an ideal medium to produce highly undercooled liquid samples and to investigate the homogeneous solidification process, free from wall effects. The filaments exit from cryogenic capillary nozzles into a vacuum chamber, to cool down very fast by surface evaporation. Finite size radius leads to a temperature gradient across the filament, determined by thermal conductivity, and, possibly, to a velocity gradient as well. The filaments are monitored by laser shadowgraphy, and analyzed by means of high performance Raman spectroscopy. Real-time measurements in the rotational and vibrational spectral regions reveal the structure and temperature along the filaments, allowing to track the crystal growth process. The high spatial resolution of Raman spectroscopy allows observing in situ the structural changes of the liquid microjets, with a time resolution of ∼ 10 ns. The filaments of pure para-H2 can be cooled down to 9 K (65% of its melting point at 13.8 K), while staying liquid, before eventually solidifying into a metastable polymorph. Crystallization kinetics revealed a growth rate of 33 cm/s, much higher than expected for a thermally activated process. The time and spatial control attained in these experiments offers new opportunities for investigating the processes of nonequilibrium phase transformations in undercooled fluids, as well as the propagation of liquid jets into a rarefied gas media. © 2012 American Institute of PhysicsThis work has been supported by the the Spanish Ministerio de Ciencia e Innovacion, through grants FIS2007-61430, FIS2010-22064-C02-01, and HD2008-0068, by the Helmholtz Gemeinschaft, through grant VH-NG-331, and by the German academic exchange service (DAAD) under reference Nr. 50025171.Peer reviewe

Observation of the Efimov state of the helium trimer

Quantum theory dictates that upon weakening the two-body interaction in a three-body system, an infinite number of three-body bound states of a huge spatial extent emerge just before these three-body states become unbound. Three helium atoms have been predicted to form a molecular system that manifests this peculiarity under natural conditions without artificial tuning of the attraction between particles by an external field. Here we report experimental observation of this long predicted but experimentally elusive Efimov state of $^{4}$He$_{3}$ by means of Coulomb explosion imaging. We show spatial images of an Efimov state, confirming the predicted size and a typical structure where two atoms are close to each other while the third is far away

Time-Resolved study of crystallization in deeply cooled liquid para-hidrogen

PACS numbers: 67.63.Cd, 33.20.Fb, 64.60.My, 64.70.dgWe present real-time measurements of the crystallization process occurring in liquid para-hydrogen (para-H2) quenched to ≈0.65Tm (Tm=13.8   K is the melting point of bulk liquid para-H2). The combination of high spatial resolution Raman spectroscopy and liquid microjet generation allows, in situ, capturing structural changes with ∼10-8  s time resolution. Our results provide a crystal growth rate that rules out a thermally activated freezing process and reveal that the quenched melt freezes into a metastable polymorph, which undergoes a structural transition. The achieved temporal control offers new opportunities for exploring the elementary processes of nonequilibrium phase transformations in supercooled liquids.We acknowledge financial support from the Helmholtz Gemeinschaft, through Grant No. VH-NG-331, and the Spanish Ministerio de Ciencia e Innovacion, through Grants No. FIS2010-22064-C02-01 and No. HD2008- 0068. We acknowledge travel support from the German academic exchange service (DAAD) under reference No. 50025171.Peer reviewe

Crystallization of Undercooled Quantum Liquids: para-H2, ortho-D2, and their mixtures with Ne

QFC2015, University Paul Sabatier in Toulouse, France, from June 7th to 11th, 2015; https://qfc2015.sciencesconf.org/We have extended the experimental production of liquid microjets (filaments) in vacuum, first realized by Faubel et al. [1], to studying the crystallization of undercooled quantum liquids: para-hydrogen (pH2), ortho-deuterium (oD2), and their mixtures with Ne. These highly collimated filaments, less than 10 microns in diameter, are an ideal medium to produce undercooled liquid samples and to investigate the homogeneous solidification process, free from wall effects [2]. The filaments exit from cryogenic capillary nozzles into vacuum, to cool down fast by surface evaporation, although with a temperature gradient across the jet due to their finite size radius and thermal conductivity. The filaments are monitored by laser shadowgraphy, and analyzed by means of high performance Raman spectroscopy [3], revealing their structure and temperature. The high spatial resolution of Raman spectroscopy allows observing in situ the structural changes of the liquid microjets, with a time resolution of ~10 ns. The filaments of pure pH2 can be cooled down to 9 K (normal melting point at 13.8 K), before eventually solidifying at a crystal growth rate of ~33 cm/s [4]. Filaments of diluted mixtures of oD2 and pH2 show a significant slowdown in the crystallization kinetics with respect to the pure substances [5], which is more pronounced in their mixtures with small amounts of Ne impurity. In the case of the pH2/oD2 mixtures, the observed slowdown can be interpreted in terms of a different effective size, caused by a purely mass-induced difference in zero-point quantum delocalization. This effect is confirmed in the mixtures with Ne, with a much larger quantum effective size ratio. References [1] M. Faubel, S. Schlemmer, and J. P. Toennies, Z. Phys D 10, 269 (1988). [2] R. E. Grisenti, R. A. Costa-Fraga, N. Petridis, R. Dorner, and J. Deppe, EuroPhys. Lett. 73, 540-546 (2006). [3] S. Montero, J. H. Morilla, G. Tejeda, and J. M. Fernandez, Eur. Phys. J. D 52, 31-34 (2009). [4] M. Kühnel, J. M. Fernández, G. Tejeda, A. Kalinin, S. Montero, and R. E. Grisenti, Phys. Rev. Lett. 106, 245301 (2011). [5] M. Kühnel, J. M. Fernández, F. Tramonto, G. Tejeda, E. Moreno, A. Kalinin, M. Nava, D. E. Galli, S. Montero, and R. E. Grisenti. Phys. Rev. B 89, 180201(R) (2014).Peer Reviewe

Frustrated solidification in microjets of undercooled liquid hydrogen mixtures

Novel experiments on undercooled liquid microjets (filaments) of para-hydrogen (p-H2) and ortho-deuterium (o-D2) mixtures will be reported. These highly collimated filaments, less than 10 microns in diameter, are an ideal medium to produce undercooled liquid samples and to investigate the homogeneous solidification process, free from wall effects [1]. The filaments exit from cryogenic capillary nozzles into vacuum, to cool down fast by surface evaporation, with a temperature gradient across the jet due to their finite size radius and thermal conductivity. The filaments are monitored by laser shadowgraphy, and analyzed by means of high performance Raman spectroscopy [2], revealing their structure and temperature. The high spatial resolution of Raman spectroscopy allows observing in situ the structural changes of the liquid microjets, with a time resolution of ~10 ns. The filaments of pure p-H2 can be cooled down to 9 K (normal melting point at 13.8 K), before eventually solidifying at a crystal growth rate of ~33 cm/s [3]. Crystal growth rate in o-D2 is ~¿2 smaller, consistent with a collision-limited process [4]. Our new experiments also show that adding small amounts of o-D2 to the p-H2 sample leads to a dramatic slowing down in the crystallization kinetics of the mixture. Phase transformations in undercooled liquids, and especially the understanding of the exact interplay between crystallization and glass formation, still poses great challenges to both theory and experiments [5]. One possible framework to explain the origin of the slowing down of the dynamics in glass-forming liquids is offered by the concept of geometric frustration associated to the development of locally favoured structures in the undercooled liquid. Simulation studies have reported a correlation between specific structural features and slowed dynamics in a variety of model systems, but the experimental demonstration of such an intrinsic link has proven challenging so far. Here, that link is supported by our measurements on the slowing down in the crystallization kinetics of diluted mixtures of o-D2 in p-H2 in liquid microjets. Full path-integral Monte Carlo simulations show that the observed effect is a result of the (weak) zero-point contribution to the interaction potential between the particles. This favours the development in the undercooled liquid mixture of icosahedral local structures around the o-D2 solute molecules, and thus frustrates the p-H2 crystal growth. While our work strongly supports the view of an intrinsic link between local order and frustrated crystallization, it provides as well the first experimental evidence for the role played by quantum fluctuations during structural transformations in undercooled liquids. [1] R. E. Grisenti, R. A. Costa-Fraga, N. Petridis, R. Dorner, and J. Deppe, EuroPhys. Lett. 73, 540-546 (2006). [2] S. Montero, J. H. Morilla, G. Tejeda, and J. M. Fernandez, Eur. Phys. J. D 52, 31-34 (2009). [3] M. Kühnel, J. M. Fernández, G. Tejeda, A. Kalinin, S. Montero, and R. E. Grisenti, Phys. Rev. Lett. 106, 245301 (2011). [4] J. M. Fernández, M. Kühnel, G. Tejeda, A. Kalinin, R. E. Grisenti, and S. Montero, AIP Conf. Proc. 1501, 1296-1304 (2012). [5] M. D. Ediger and P. Harrowell, J. Chem. Phys. 137, 080901 (2012).Peer Reviewe

Measuring the temperature of the coldest liquid water

Bundesministerium für Bildung und Forschung (05K13RF5), and Spanish Ministerio de Economía y Competitividad (FIS2013-48275-C2)Peer reviewe

Crystallization in undercooled liquid microjets of H2/D2 mixtures

Novel experiments on undercooled liquid microjets (filaments) of para-hydrogen (p-H2) and ortho-deuterium (o-D2) mixtures will be reported. These highly collimated filaments, less than 10 microns in diameter, are an ideal medium to produce undercooled liquid samples and to investigate the homogeneous solidification process, free from wall effects [1]. The filaments exit from cryogenic capillary nozzles into vacuum, to cool down fast by surface evaporation, with a temperature gradient across the jet due to their finite size radius and thermal conductivity. The filaments are monitored by laser shadowgraphy, and analyzed by means of high performance Raman spectroscopy [2], revealing their structure and temperature. The high spatial resolution of Raman spectroscopy allows observing in situ the structural changes of the liquid microjets, with a time resolution of ~10 ns. The filaments of pure p-H2 can be cooled down to 9 K (normal melting point at 13.8 K), before eventually solidifying at a crystal growth rate of ~33 cm/s [3]. Crystal growth rate in o-D2 is ~¿2 smaller, consistent with a collision-limited process [4]. Our experiments on diluted mixtures of o-D2 in p-H2 also show a dramatic slowing down in the crystallization kinetics of the mixture. Full path-integral Monte Carlo simulations show that the observed effect is a result of the (weak) zero-point contribution to the interaction potential between the particles. This favours the development in the undercooled liquid mixture of icosahedral local structures around the o-D2 solute molecules, and thus frustrates the p-H2 crystal growth. While our work strongly supports the view of an intrinsic link between local order and frustrated crystallization, it provides as well the first experimental evidence for the role played by quantum fluctuations during structural transformations in undercooled liquids. [1] R. E. Grisenti, R. A. Costa-Fraga, N. Petridis, R. Dorner, and J. Deppe, EuroPhys. Lett. 73, 540-546 (2006). [2] S. Montero, J. H. Morilla, G. Tejeda, and J. M. Fernandez, Eur. Phys. J. D 52, 31-34 (2009). [3] M. Kühnel, J. M. Fernández, G. Tejeda, A. Kalinin, S. Montero, and R. E. Grisenti, Phys. Rev. Lett. 106, 245301 (2011). [4] J. M. Fernández, M. Kühnel, G. Tejeda, A. Kalinin, R. E. Grisenti, and S. Montero, AIP Conf. Proc. 1501, 1296-1304 (2012).Peer Reviewe

Experiments on undercooled liquid microjets of H2, D2 and their mixtures with Ne

Conferencia invitada; ISMB2015, 28 junio al 3 de julio de 2015, Segovia (España); http://www.ucm.es/ismbWe have extended the experimental production of liquid microjets (filaments) in vacuum, first realized by Faubel et al. [1], to studying the crystallization of undercooled quantum liquids: para-hydrogen (pH2), ortho-deuterium (oD2), and their mixtures with Ne. These highly collimated filaments, less than 10 microns in diameter, are an ideal medium to produce undercooled liquid samples and to investigate the homogeneous solidification process, free from wall effects [2]. The filaments exit from cryogenic capillary nozzles into vacuum, to cool down fast by surface evaporation, although with a temperature gradient across the jet due to their finite size radius and thermal conductivity. The filaments are monitored by laser shadowgraphy, and analyzed by means of high performance Raman spectroscopy [3], revealing their structure and temperature. The high spatial resolution of Raman spectroscopy allows observing in situ the structural changes of the liquid microjets, with a time resolution of ~10 ns. The filaments of pure pH2 can be cooled down to 9 K (normal melting point at 13.8 K), before eventually solidifying at a crystal growth rate of ~33 cm/s [4]. Filaments of diluted mixtures of oD2 and pH2 show a significant slowdown in the crystallization kinetics with respect to the pure substances [5], which is more pronounced in their mixtures with small amounts of Ne impurity. In the case of the pH2/oD2 mixtures, the observed slowdown can be interpreted in terms of a different effective size, caused by a purely mass-induced difference in zero-point quantum delocalization. This effect is confirmed in the mixtures with Ne, with a much larger quantum effective size ratio. References [1] M. Faubel, S. Schlemmer, and J. P. Toennies, Z. Phys D 10, 269 (1988). [2] R. E. Grisenti, R. A. Costa-Fraga, N. Petridis, R. Dorner, and J. Deppe, EuroPhys. Lett. 73, 540-546 (2006). [3] S. Montero, J. H. Morilla, G. Tejeda, and J. M. Fernandez, Eur. Phys. J. D 52, 31-34 (2009). [4] M. Kühnel, J. M. Fernández, G. Tejeda, A. Kalinin, S. Montero, and R. E. Grisenti, Phys. Rev. Lett. 106, 245301 (2011). [5] M. Kühnel, J. M. Fernández, F. Tramonto, G. Tejeda, E. Moreno, A. Kalinin, M. Nava, D. E. Galli, S. Montero, and R. E. Grisenti. Phys. Rev. B 89, 180201(R) (2014).Peer Reviewe