title: Hydrogen clusters that remain fluid at low temperature.
abstract: Superfluidity of hydrogen, predicted three decades ago, continues to elude experimental observation, due to the high freezing temperature of H2 at T=13.8 K. Here, large para-H2 clusters are obtained in a cryogenic pulsed free jet expansion and are studied via nonlinear Raman spectroscopy. Clusters formed from neat pH_{2} are solid as evidenced by the characteristic splitting of the rotational S0(0) line. However, clusters formed of highly diluted pH_{2} (< or = 1%) in He have a single S0(0) line and remain liquid at the estimated superfluid transition temperature of T=1-2 K.
authors.affiliation: Department of Chemistry, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Kirill
authors.initials: K
authors.lastname: Kuyanov-Prozument
authors.forename: Andrey F
authors.initials: AF
authors.lastname: Vilesov