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Atomic probes in normal fluid, superfluid and solid helium: spectroscopy and imaging

English title Atomic probes in normal fluid, superfluid and solid helium: spectroscopy and imaging
Applicant Weis Antoine
Number 129831
Funding scheme Project funding
Research institution Département de Physique Université de Fribourg
Institution of higher education University of Fribourg - FR
Main discipline Condensed Matter Physics
Start/End 01.04.2010 - 31.03.2012
Approved amount 199'194.00
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All Disciplines (2)

Discipline
Condensed Matter Physics
Other disciplines of Physics

Keywords (14)

superfluid helium; solid helium; ultrafast laser spectroscopy; quantized vortices; atomic bubbles; quantum fluids; quantum crystals; matrix isolation spectroscopy; quantum fluids and solids; liquid and solid helium; snowballs; laser spectroscopy; ultrafast dynamics; pump-probe laser spectroscopy

Lay Summary (English)

Lead
Lay summary
The Fribourg Atomic Physics group (FRAP) has a world-leading expertise in the study of atoms and molecules embedded into liquid and solid helium matrices. This unique variant of matrix isolation spectroscopy in quantum fluids and solids is closely related to defect spectroscopy in heavier rare gas and hydrogen solids and in doped helium nano-droplets.On one hand, we are interested in gaining a deeper understanding of the modification of free atomic properties by superfluid? normal fluid, and solid helium matrices, which, together with model calculations, gives us a quantitative insight into the structure, symmetry, and dynamics of the local trapping sites in these unusual matrices. On the other hand, we use the spectroscopic and time-resolved interrogation of the dopants in order to ivestigate the properties of the quantum fluid/solid and the dynamics of the defect surrounding. This approach allows us to investigate the quantum fluids and solids at the nanometer and femtosecond scales.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Formation of Metallic Nanowires by Laser Ablation in Liquid Helium
Lebedev V, Moroshkin P, Grobety B, Gordon E, Weis A (2011), Formation of Metallic Nanowires by Laser Ablation in Liquid Helium, in JOURNAL OF LOW TEMPERATURE PHYSICS, 165(3-4), 166-176.
Laser ablation and spectroscopy of copper in liquid and solid He-4
Moroshkin P, Lebedev V, Weis A (2011), Laser ablation and spectroscopy of copper in liquid and solid He-4, in PHYSICAL REVIEW A, 84(5), 052519-1-052519-9.
Phonon generation in condensed He-4 by laser-excited atomic bubbles
Moroshkin P, Lebedev V, Weis A (2011), Phonon generation in condensed He-4 by laser-excited atomic bubbles, in EPL, 96(2), 26002-p1-26002-p6.
Spectroscopy of barium atoms in liquid and solid helium matrices
Lebedev V, Moroshkin P, Weis A (2011), Spectroscopy of barium atoms in liquid and solid helium matrices, in PHYSICAL REVIEW A, 84(2), 022502-1-022502-9.
Spectroscopy of Nonspherical Atomic Bubbles in Solid Helium
Lebedev V, Moroshkin P, Weis A (2011), Spectroscopy of Nonspherical Atomic Bubbles in Solid Helium, in JOURNAL OF PHYSICAL CHEMISTRY A, 115(25), 7169-7179.
Vibronic Transitions of Atomic Bubbles in Condensed He-4
Moroshkin P, Lebedev V, Weis A (2011), Vibronic Transitions of Atomic Bubbles in Condensed He-4, in JOURNAL OF LOW TEMPERATURE PHYSICS, 162(5-6), 710-717.
Spectroscopy of Cs-2, RbCs, and Rb-2 in solid He-4
Moroshkin P, Hofer A, Lebedev V, Weis A (2010), Spectroscopy of Cs-2, RbCs, and Rb-2 in solid He-4, in JOURNAL OF CHEMICAL PHYSICS, 133(17), 174510-1-174510-7.
Spectroscopy of the copper dimer in normal fluid, superfluid, and solid He-4
Lebedev V, Moroshkin P, Toennies JP, Weis A (2010), Spectroscopy of the copper dimer in normal fluid, superfluid, and solid He-4, in JOURNAL OF CHEMICAL PHYSICS, 133(15), 154508-1-154508-8.
Nanowire formation by gold nano-fragment coalescence on quantized vortices in He II
Moroshkin P, Lebedev V, Grobety B, Neururer C, Gordon EB, Weis A (2010), Nanowire formation by gold nano-fragment coalescence on quantized vortices in He II, in EPL, 90(3), 34002-p1-34002-p5.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
LiMat-Day 2011 11.11.2011 Bern, Switzerland
MATRIX-2011 10.07.2011 Vancouver, Canada
ECAMP X: 10th European Conference on Atoms, Molecules, and Photons 05.07.2010 Salamanca, Spain


Awards

Title Year
EPL Best of 2011 2012
Faculty of Science Prize for best PhD thesis in experimental science 2012
Bronze Award for best student oral presentation at ANGEL 2010 2010

Associated projects

Number Title Start Funding scheme
119786 Spectroscopy of electronic, atomic, ionic and exciplex bubbles in quantum solids 01.04.2008 Project funding

Abstract

15 years ago the main applicant (Prof. A. Weis) has pioneered the field of doped solid He spectroscopy and has reached a world-leading position in this field. In past SNF-funding periods our team at the Physics Department of the University of Fribourg has concentrated on the optical and magneto-optical spectroscopy of metallic impurity atoms and molecules in solid He matrices. During the last funding period we have make some remarkable new observations which incite us to slightly shift gears in the continuation proposal. In three subprojects we plan to deepen previously gained knowledge and to advance into new areas:Subproject A: Doped vortices in superfluid helium. Foreign atoms trapped in solid He matrices are practically immobile, a feature that was used in all of previous high-accuracy spectroscopic studies. On the other hand, impurity atoms in superfluid He can move freely and may become trapped on quantized vortex lines. Although the trapping of He+ ions and free electrons had already been observed in 1970ies, no investigation of the interaction of neutral atomic dopants with vortices was presented up to date. Recently we have shown, that neutral metal atoms may indeed become trapped at vortex lines, where they aggregate into extremely thin and long filaments (nanowires). We will use our past spectroscopic expertise to explore, whether impurity atoms can be used as moving tracers -- that do not disturb the motion of the liquid -- for the observation of the flow of superfluid He. Laser-induced fluorescence will serve as the the monitoring signal. We propose experiments aimed at the visual observation of single metal atoms in superfluid He and the investigation of the nanofilament formation mechanism by high resolution CCD imaging.Subproject B:Revealing the difference between normal fluid and superfluid helium. The defects formed by impurity atoms in superfluid and solid He - atomic bubbles are very well studied and understood. However, very little is known about the foreign atoms in normal fluid He. The actual role of superfluidity in the atomic bubble structure and energetics is not clear. We propose a new spectroscopic experiment that will provide the information on the validity of the atomic bubble model for normal fluid He and, more specifically, to reveal microscopic signatures of superfluidity.Subproject C: Femtosecond atomic bubble dynamics. In the past we have shown that atomic bubbles are efficient sensors exploring the local structure of condensed He. Because of the quantum nature of the He matrix the surrounding of the embedded atoms is strongly affected by the size and symmetry of the dopant impurity. Structural changes of the latter imply corresponding structural changes of the former. Such changes are expected to occur on picosecond time scales. Here we propose to explore these dynamic processes by measuring the response of the medium following a sudden atomic excitation in spectroscopic femtosecond pump-probe experiments. This project will be performed in close collaboration with Prof. T. Feurer at the University of Bern who will provide the femtosecond oscillator and his leading edge know-how on the spectral and temporal tailoring of femtosecond pulses.
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