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Imaging the photodynamics of doped helium nanodroplets

English title Imaging the photodynamics of doped helium nanodroplets
Applicant Drabbels Marcel
Number 112193
Funding scheme Project funding (Div. I-III)
Research institution Institut des sciences et ingénierie chimiques EPFL - SB - ISIC
Institution of higher education EPF Lausanne - EPFL
Main discipline Physical Chemistry
Start/End 01.04.2006 - 31.03.2008
Approved amount 179'782.00
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Keywords (8)

helium droplets; photodissociation; photoionization; ion imaging; photoelectron spectroscopy; molecular dynamics; helium nanodroplets; superfluidity

Lay Summary (English)

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Lay summary
Liquid helium is a highly quantum system and as such has some remarkable properties. One of the most striking is undoubtedly that 4He becomes superfluid at temperatures below 2.17 K. Superfluid helium has a vanishing small viscosity and objects can move through the liquid without experiencing any friction provided their velocity is below the so-called critical Landau velocity of 58 m/s. Although many properties of liquid helium have been extensively studied since it was first liquefied almost a century ago, it mainly concerns macroscopic properties. Studies at a microscopic level have been severely hampered by the fact that species do not dissolve into bulk helium. This situation changed dramatically when in the beginning of the 1990’s techniques for the production helium nanodroplets became available and it was found that molecular probes can be readily introduced into these droplets. The current research program is a continuation of our efforts to gain a more profound understanding on the interaction of neutral and charged molecular species with this quantum fluid. Currently two different types of experiments are being carried out. Experiments in which molecular species residing in helium droplets are dissociated by UV light are intended to elucidate the mechanism underlying the translational motion of neutral species in superfluid helium. These experiments make use of spectroscopic and ion imaging techniques that enable the determination of the velocity distributions of products that have left the droplets. These distributions provide detailed information on the kinetic energy and momentum transfer from the photofragments to the quantum fluid. In other experiments atoms or molecules embedded in helium droplets are photoionized and the kinetic energy of the escaping electrons is determined. These experiments are intended to provide inside into the solvation and translational dynamics of charged particles in liquid helium. Besides experiments that focus on these fundamental interactions, experiments are planned that make use of the special properties of liquid helium to probe properties of molecules that are otherwise difficult if not impossible to obtain.
Direct link to Lay Summary Last update: 21.02.2013

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Associated projects

Number Title Start Funding scheme
119789 Photodynamics of doped helium nanodroplets 01.04.2008 Project funding (Div. I-III)
103527 Imaging the photodynamics in liquid helium droplets 01.04.2004 Project funding (Div. I-III)

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