A5060642937- Quantum, superfluid, helium dynamics
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Chemical Physics Studies
- Phase Equilibria and Thermodynamics
- Spectroscopy and Laser Applications
- Physics of Superconductivity and Magnetism
- High-pressure geophysics and materials
- Gas Sensing Nanomaterials and Sensors
- Spacecraft and Cryogenic Technologies
- Atmospheric Ozone and Climate
- nanoparticles nucleation surface interactions
- Methane Hydrates and Related Phenomena
- Lattice Boltzmann Simulation Studies
- Spectroscopy and Quantum Chemical Studies
- Astrophysical Phenomena and Observations
University of Southern California
2019-2024
Finding the lowest energy configuration of N unit charges on a sphere, known as Thomson's problem, is long-standing query which has only been studied via numerical simulations. We present its physical realization using multiply charged He nanodroplets. The charge positions are determined by x-ray coherent diffractive imaging with Xe contrast agent. In neutral droplets, filaments resulting from atoms condensing quantum vortices observed. Unique to however, clusters that condense distributed...
Infrared (IR) spectroscopy using ultracold helium nanodroplet matrices has proven to be a powerful method interrogate encapsulated ions, molecules, and clusters. Due the droplets' high ionization potential, optical transparency, ability pick up dopant droplets offer unique modality probe transient chemical species produced via photo- or electron impact ionization. In this work, were doped with acetylene molecules ionized impact. Ion-molecule reactions within droplet volume yield larger...
Here, we show that electron impact ionization of helium (He) droplets doped with water molecules and clusters yield Zundel cations embedded in the consisting a few thousand atoms. Infrared spectra OH-stretching range were obtained using release from upon laser excitation. The He appear to have about factor 10 narrower bands similar matrix shifts as compared those via tagging Ar results confirm calculated structure free ion, where proton is equidistant two units. effect environment on ions...
The electron impact ionization of helium droplets doped with ethylene molecules and clusters yields diverse CXHY+ cations embedded in the droplets. primarily produces C2H2+, C2H3+, C2H4+, CH2+, whereas larger carbocations are produced upon reactions primary ions molecules. vibrational excitation leads to release bare a few atoms attached. laser spectra show well resolved bands wavenumber widths—an order magnitude less than those previously obtained solid matrices or molecular beams by...
Observation of the free rotation molecules in helium droplets enabled microscopic study interaction quantum rotors with a superfluid environment at T = 0.4 K. This work extends studies to molecular cations, such as methenium, CH3+. The spectrum v3 band CH3+ around 3130 cm–1 has three prominent peaks assigned rotational structure band. While is an oblate top, it behaves prolate top. effect ascribed strong binding two He atoms along figure axis ion. Our results indicate that other within first...
Superfluid helium nanodroplets are unique nanomatrices for the isolation and study of transient molecular species, such as radicals, carbenes, ions. In this work, isomers C3H4+ were produced upon electron ionization propyne allene molecules interrogated via infrared spectroscopy inside He nanodroplet matrices. It was found that spectrum has at least three distinct groups bands. The relative intensities bands depend on precursor employed its pickup pressure, which indicates presence different...
Previous single-pulse extreme ultraviolet and x-ray coherent diffraction studies revealed that superfluid $^{4}\mathrm{He}$ droplets obtained in a free jet expansion acquire sizable angular momentum, resulting significant centrifugal distortion. Similar experiments with normal fluid $^{3}\mathrm{He}$ may help elucidate the origin of large degree rotational excitation highlight similarities differences dynamics droplets. Here, we present comparison shapes isolated following corresponding...
Helium droplets are unique hosts for isolating diverse molecular ions infrared spectroscopic experiments. Recently, it was found that electron impact ionization of ethylene clusters embedded in helium produces carbocations containing three and four carbon atoms, indicating effective ion-molecule reactions. In this work, similar experiments reported but with the saturated hydrocarbon precursor ethane. distinction to ethylene, no characteristic bands larger covalently bound were found,...
Superfluid helium nanodroplets are an ideal environment for the formation of metastable, self-organized dopant nanostructures. However, presence vortices often hinders their formation. Here, we demonstrate generation vortex-free and explore size range in which they can be produced. From x-ray diffraction images xenon-doped droplets, identify that single compact structures, assigned to aggregation, prevail up 10^{8} atoms per droplet. This finding builds basis exploring assembly...
Clusters in 3 He and 4 nanodroplets reveal markedly different shapes showcasing the effect of superfluidity on aggregation.
Silver clusters were assembled in helium droplets of different sizes ranging from 104 to 1011 atoms. The heated upon laser irradiation at 355 nm, and evaporation dynamics He atoms studied by quadrupole mass spectroscopy using signals He+, He2+, He4+ splitter ions. We found that for containing less than 107 the leads However, breakup large into smaller ones.
Superfluid helium nanodroplets are an ideal environment for the formation of metastable, self-organized dopant nanostructures. However, presence vortices often hinders their formation. Here, we demonstrate generation vortex-free and explore size range in which they can be produced. From x-ray diffraction images xenon-doped droplets, identify that single compact structures, assigned to aggregation, prevail up $10^8$ atoms per droplet. This finding builds basis exploring assembly...