Browsing by Author "Moroshkin, P."

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Bound-bound transitions in the emission spectra of Ba+-He excimer
(2016-05-19)
Moroshkin, P.
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Kono, K.
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物理研究所
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Institute of Physics
We present an experimental and theoretical study of the emission and absorption spectra of the Ba+ ions and Ba+*He excimer quasimolecules in the cryogenic Ba-He plasma. We observe several spectral features in the emission spectrum, which we assign to the electronic transitions between bound states of the excimer correlating to the 6(2)P(3/2) and 5(2)D(3/2,5/2) states of Ba+. The resulting Ba+(5(2)D(J)) He is a metastable electronically excited complex with orbital angular momentum L = 2, thus expanding the family of known metal-helium quasimolecules. It might be suitable for high-resolution spectroscopic studies and for the search for new polyatomic exciplex structures.
Dynamics of the Vortex-Particle Complexes Bound to the Free Surface of Superfluid Helium
(2019-05-03)
Moroshkin, P.
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Leiderer, P.
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Kono, K.
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Inui, S.
;
Tsubota, M.
We present an experimental and theoretical study of the 2D dynamics of electrically charged nanoparticles trapped under a free surface of superfluid helium in a static vertical electric field. We focus on the dynamics of particles driven by the interaction with quantized vortices terminating at the free surface. We identify two types of particle trajectories and the associated vortex structures: vertical linear vortices pinned at the bottom of the container and half-ring vortices traveling along the free surface of the liquid.
Imaging and time-resolved study of laser-induced fluorescence of dysprosium atoms injected into superfluid helium
(2020-04-28)
Moroshkin, P.
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Kono, K.
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國際半導體學院
;
International College of Semiconductor Technology
We study the time evolution of the cloud of Dy atoms dispersed in superfluid helium and investigate the possibility of using these atoms as tracers for the imaging of superfluid-helium flows. The atoms are produced by pulsed laser ablation and are visualized via their laser-induced fluorescence. It turns out that the observation time is limited by the optical pumping of the atomic population into a nonabsorbing metastable state which is also responsible for the saturation of the fluorescence yield observed earlier.
Laser spectroscopy of phonons and rotons in superfluid helium doped with Dy atoms
(2018-03-09)
Moroshkin, P.
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Borel, A.
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Kono, K.
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物理研究所
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Institute of Physics
We report the results of a high-resolution laser-spectroscopy study of dysprosium atoms injected into superfluid He-4. A special attention is paid to the transitions between the inner 4f and 5d electronic shells of Dy. The characteristic gap is observed between the zero-phonon line and the phonon wing in the experimental excitation spectrum that arises due to the peculiar structure of the phonon-roton spectrum of superfluid He. This observation resolves the longstanding discrepancy between the studies of bulk superfluid He and He nanodroplets.
Metallic nanowires and mesoscopic networks on a free surface of superfluid helium and charge-shuttling across the liquid-gas interface
(2016-10-14)
Moroshkin, P.
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Batulin, R.
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Leiderer, P.
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Kono, K.
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物理研究所
We investigate the motion of electrically charged metallic nano- and microparticles produced by laser ablation in He gas and injected into superfluid helium. In the presence of a vertical static electric field, the particles either perform a repetitive shuttle-like motion transporting the charge across the liquid-gas interface or become trapped under the free surface of liquid He and coalesce into long filaments and complex two-dimensional mesoscopic networks. A classical electrohydrodynamic model is used to describe the motion of charged microparticles in superfluid He. The resulting filaments and networks are analyzed using electron microscopy. It is demonstrated that each filament is in fact composed of a large number of nanowires with a characteristic diameter of order of 10 nm and extremely large aspect ratios.
Motion of metallic microparticles in superfluid helium in the presence of space charge
(2017-04-01)
Moroshkin, P.
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Leiderer, P.
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Kono, K.
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物理研究所
;
Institute of Physics
We report an experimental and theoretical study of the motion of metallic micro-and nanoparticles in cryogenic superfluid helium in the presence of a static electric field. Depending on the polarity of the applied field, the system is charged with a large number of positive ions or free electrons. For the electrons, we observe the formation of a negative charge layer above the free surface of liquid He and a shuttle-like motion of metallic particles between this layer and the positively charged bottom electrode. For the positive ions, the positive space charge is created in the liquid and the particle motion resembles bouncing off the (negatively charged) bottom electrode. The observations are explained by a theoretical model based on classical electrostatics and hydrodynamics. Published by AIP Publishing.
Perturbations of a Free Surface of Superfluid Helium by the Ion Wind Produced by a Corona Discharge Above the Liquid
(2019-05-01)
Moroshkin, P.
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Leiderer, P.
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Kono, K.
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電子物理學系
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Department of Electrophysics
We report on experimental observations of the deformations of a free surface of superfluid 4He in the presence of the corona discharge above the liquid. The effect is attributed to the impact of the ion wind generated by the discharge.
Taylor cone and electrospraying at a free surface of superfluid helium charged from below
(2017-05-19)
Moroshkin, P.
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Leiderer, P.
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Moeller, Th. B.
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Kono, K.
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物理研究所
Electrically charged metallic micro-and nanoparticles are trapped under a free surface of superfluid He in a vertical static electric field. We observe a static deformation of the charged liquid surface in the form of a Taylor cone and the emission of a charged liquid helium jet (electrospray). Our numeric calculations reproduce the static shape of the cone.
Trapping of metallic nanoparticles under the free surface of superfluid helium in a static electric field
(2019-07-01)
Moroshkin, P.
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Leiderer, P.
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Moeller, Th. B.
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Kono, K.
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國際半導體學院
Electrically charged metallic microparticles and nanoparticles have been trapped under a free surface of superfluid He-4 in a vertical static electric field. We report the details of the trapping technique and the observed dynamics of the trapped particles moving along the surface and driven by surface waves, by a static horizontal electric field, and by a thermal counterflow within the surface layer of liquid He.
Zero-phonon lines in the spectra of dysprosium atoms in superfluid helium
(2019-03-18)
Moroshkin, P.
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Konol, K.
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國際半導體學院
;
International College of Semiconductor Technology
We present an experimental study of a zero-phonon line (ZPL) in the absorption spectrum of Dy atoms solvated in superfluid He. The dopants reside in nanometer-sized spherical cavities known as atomic bubbles. We observe a temperature-dependent broadening of ZPL in the absorption spectrum. The effect is attributed to the scattering of thermal phonons on the atomic bubble that leads to the dephasing of the Dy transition dipole. The extrapolated ZPL intrinsic spectral width at zero temperature is 2300 times larger than the natural linewidth in a free atom. This can be assigned to a fast radiationless quenching of the upper state of the studied transition.