title: Helium superfluidity. Shapes and vorticities of superfluid helium nanodroplets.
abstract: Helium nanodroplets are considered ideal model systems to explore quantum hydrodynamics in self-contained, isolated superfluids. However, exploring the dynamic properties of individual droplets is experimentally challenging. In this work, we used single-shot femtosecond x-ray coherent diffractive imaging to investigate the rotation of single, isolated superfluid helium-4 droplets containing ~10(8) to 10(11) atoms. The formation of quantum vortex lattices inside the droplets is confirmed by observing characteristic Bragg patterns from xenon clusters trapped in the vortex cores. The vortex densities are up to five orders of magnitude larger than those observed in bulk liquid helium. The droplets exhibit large centrifugal deformations but retain axially symmetric shapes at angular velocities well beyond the stability range of viscous classical droplets.
authors.affiliation: Department of Chemistry, University of Southern California (USC), Los Angeles, CA 90089, USA.
authors.forename: Luis F
authors.initials: LF
authors.lastname: Gomez
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
authors.forename: Ken R
authors.initials: KR
authors.lastname: Ferguson
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Cryan
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA. Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA.
authors.forename: Camila
authors.initials: C
authors.lastname: Bacellar
authors.affiliation: Department of Chemistry, University of Southern California (USC), Los Angeles, CA 90089, USA.
authors.forename: Rico Mayro P
authors.initials: RM
authors.lastname: Tanyag
authors.affiliation: Department of Chemistry, University of Southern California (USC), Los Angeles, CA 90089, USA.
authors.forename: Curtis
authors.initials: C
authors.lastname: Jones
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Schorb
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Denis
authors.initials: D
authors.lastname: Anielski
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Belkacem
authors.affiliation: Department of Physics and Astronomy, USC, Los Angeles, CA 90089, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Bernando
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany. Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Boll
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
authors.forename: John
authors.initials: J
authors.lastname: Bozek
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Carron
authors.affiliation: Advanced Light Source, LBNL, Berkeley, CA 94720, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.affiliation: CFEL, DESY, Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Tjark
authors.initials: T
authors.lastname: Delmas
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße, 85741 Garching, Germany.
authors.forename: Lars
authors.initials: L
authors.lastname: Englert
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Sascha W
authors.initials: SW
authors.lastname: Epp
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany. Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Erk
authors.affiliation: Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany. Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Foucar
authors.affiliation: PNSensor GmbH, Otto-Hahn-Ring 6, 81739 München, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Hartmann
authors.affiliation: Advanced Light Source, LBNL, Berkeley, CA 94720, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Hexemer
authors.affiliation: PNSensor GmbH, Otto-Hahn-Ring 6, 81739 München, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Huth
authors.affiliation: Mork Family Department of Chemical Engineering and Materials Science, USC, Los Angeles, CA 90089, USA.
authors.forename: Justin
authors.initials: J
authors.lastname: Kwok
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA. Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA. Department of Physics, University of California Berkeley, Berkeley, CA 94720, USA.
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Leone
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA. Department of Physics, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Jonathan H S
authors.initials: JH
authors.lastname: Ma
authors.affiliation: National Energy Research Scientific Computing Center, LBNL, Berkeley, CA 94720, USA.
authors.forename: Filipe R N C
authors.initials: FR
authors.lastname: Maia
authors.affiliation: Physical Biosciences Division, LBNL, Berkeley, CA 94720, USA. Department of Plant and Microbial Biology, University of Calfornia Berkeley, Berkeley, CA 94720, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Malmerberg
authors.affiliation: Advanced Light Source, LBNL, Berkeley, CA 94720, USA. Department of Physics, University of California Davis, Davis, CA 95616, USA.
authors.forename: Stefano
authors.initials: S
authors.lastname: Marchesini
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA. Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Neumark
authors.affiliation: Physical Biosciences Division, LBNL, Berkeley, CA 94720, USA.
authors.forename: Billy
authors.initials: B
authors.lastname: Poon
authors.affiliation: Department of Chemistry, University of California Berkeley, Berkeley, CA 94720, USA.
authors.forename: James
authors.initials: J
authors.lastname: Prell
authors.affiliation: Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany. Deutsches Elektronen-Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany. Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Rolles
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Rudek
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany. James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Artem
authors.initials: A
authors.lastname: Rudenko
authors.affiliation: Department of Chemistry, University of Southern California (USC), Los Angeles, CA 90089, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Seifrid
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA.
authors.forename: Katrin R
authors.initials: KR
authors.lastname: Siefermann
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA.
authors.forename: Felix P
authors.initials: FP
authors.lastname: Sturm
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA.
authors.forename: Michele
authors.initials: M
authors.lastname: Swiggers
authors.affiliation: Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany. Max Planck Advanced Study Group at the Center for Free-Electron Laser Science (CFEL), Notkestraße 85, 22607 Hamburg, Germany.
authors.forename: Joachim
authors.initials: J
authors.lastname: Ullrich
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA.
authors.forename: Fabian
authors.initials: F
authors.lastname: Weise
authors.affiliation: Physical Biosciences Division, LBNL, Berkeley, CA 94720, USA.
authors.forename: Petrus
authors.initials: P
authors.lastname: Zwart
authors.affiliation: Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA. PULSE Institute, Stanford University and SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA. bostedt@slac.stanford.edu ogessner@lbl.gov vilesov@usc.edu.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bostedt
authors.affiliation: Ultrafast X-ray Science Laboratory, Chemical Sciences Division, Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA 94720, USA. bostedt@slac.stanford.edu ogessner@lbl.gov vilesov@usc.edu.
authors.forename: Oliver
authors.initials: O
authors.lastname: Gessner
authors.affiliation: Department of Chemistry, University of Southern California (USC), Los Angeles, CA 90089, USA. Department of Physics and Astronomy, USC, Los Angeles, CA 90089, USA. bostedt@slac.stanford.edu ogessner@lbl.gov vilesov@usc.edu.
authors.forename: Andrey F
authors.initials: AF
authors.lastname: Vilesov