A5062405585- Quantum, superfluid, helium dynamics
- Cold Atom Physics and Bose-Einstein Condensates
- Atomic and Subatomic Physics Research
- nanoparticles nucleation surface interactions
- Laser-induced spectroscopy and plasma
- Methane Hydrates and Related Phenomena
- Spectroscopy and Laser Applications
- X-ray Diffraction in Crystallography
- Laser-Plasma Interactions and Diagnostics
- Crystallization and Solubility Studies
- Inorganic Fluorides and Related Compounds
- Fluid Dynamics and Turbulent Flows
- Gas Sensing Nanomaterials and Sensors
- Spectroscopy and Quantum Chemical Studies
- Structural Analysis and Optimization
- Phase Equilibria and Thermodynamics
- Solidification and crystal growth phenomena
- Spacecraft and Cryogenic Technologies
- Advanced Materials and Mechanics
- Structural Engineering and Vibration Analysis
- Hydrogen Storage and Materials
- Computational Physics and Python Applications
- Adhesion, Friction, and Surface Interactions
- Laser-Matter Interactions and Applications
- Advanced Chemical Physics Studies
University of Southern California
2016-2025
Intel (United States)
2021
Patna University
1983-1985
For more than two decades, encapsulation in superfluid helium nanodroplets has served as a reliable technique for probing the structure and dynamics of molecules clusters at low temperature ≈0.37 K. Due to weak interactions between host liquid helium, good spectral resolution can usually be achieved, making droplets an ideal matrix spectroscopy wide range from infrared ultraviolet. Furthermore, rotational spectra small provides unique probe with on atomic scale. This review presents summary...
The angular momentum of rotating superfluid droplets originates from quantized vortices and capillary waves, the interplay between which remains to be uncovered. Here, rotation isolated submicrometer $^{4}\mathrm{He}$ is studied by ultrafast x-ray diffraction using a free electron laser. patterns provide simultaneous access morphology vortex arrays they host. In capsule-shaped droplets, form distorted triangular lattice, whereas arrange along elliptical contours in ellipsoidal droplets....
Magnesium atoms in liquid helium have been hypothesized to form a metastable foam structure, which layer of surrounds each magnesium atom, inhibiting their coalescence into compact cluster. This conjecture is based on the weak interaction between themselves and with was used explain observations femtosecond two-photon ionization experiments by different groups. However, this theory incongruent previous infrared spectroscopic observations, indicating formation tightly bound clusters when...
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...
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...
The methanium CH
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...
Nitrogen oxide clusters (NO)n have been studied in He droplets via infrared depletion spectroscopy and by quantum chemical calculations. The ν1 ν5 bands of cis-ON-NO dimer observed at 1868.2 1786.5 cm(-1), respectively. Furthermore, spectral the trimer tetramer located vicinity corresponding accord with computed frequencies that place NO-stretch dimer, trimer, within a few wavenumbers each other. In addition, new line 1878.1 cm(-1) close to band origin single molecules was assigned van der...
Clusters in 3 He and 4 nanodroplets reveal markedly different shapes showcasing the effect of superfluidity on aggregation.
Strong-field ionization of nanoscale clusters provides excellent opportunities to study the complex correlated electronic and nuclear dynamics near-solid density plasmas. Yet, monitoring ultrafast, nanoscopic in real-time is challenging, which often complicates a direct comparison between theory experiment. Here, near-infrared laser-induced plasma ∼600 nm diameter helium droplets are studied by femtosecond time-resolved x-ray coherent diffractive imaging. An anisotropic, ∼20 wide surface...
Electron impact ionization of superfluid helium droplets containing several thousand atoms produces a broad distribution Hen+ ions that peaks at n = 2 and decreases monotonically toward larger n. In (say 105 or more atoms), however, the He4+ signal intensity is anomalously large. We have studied mechanism for formation in large by varying duration electron excitation pulse. Droplets different average sizes were generated using expansion 20 bars 9-20 K through pulsed valve nozzle. The...
Intense laser induced plasma dynamics in sub-micron scale helium droplets are monitored by femtosecond time-resolved X-ray coherent diffractive imaging. Anisotropic surface softening and strongly anisotropic shrinking of the core observed.