A
double time-of-flight multi-electron-ion coincidence spectroscopy
technique
by Raimund
Feifel
Molecular Physics, SU
Thursday the 21st of February 10.00 o'clock at FA32
Abstract
The interpretation of the photoelectric effect by
Albert Einstein in 1905 opened the way for photoelectron spectroscopy
as pioneeringly developed in Uppsala. It reveals mainly the transitions
to singly-ionised states of the system studied.
The absorption of a single photon may also lead to the ejection of two
or more electrons from the same target species. If all the ejected
electrons can be detected in coincidence and energy analysed, the
energy levels of the multiply-ionised system can be obtained. This
experiment is in effect photoelectron spectroscopy of multiply charged
ions. Studies of dicationic states by this means are referred to as
PhotoElectron-PhotoElectron COincidence (PEPECO) spectroscopy.
In this seminar the fundamental aspects of conventional photoelectron
spectroscopy will be briefly recapitulated along with the presentation
of a novel technique recently invented for multi-electron-ion
coincidence spectroscopy. Examples of studies of single and double
photoionisation of atoms and molecules will be given and mechanisms for
multiple ionisation processes will be discussed as well as energy
relationships.
Super
lubricating nano particles
by Stefan Csillag
Nuclear Physics, SU
Thursday the 6th of Mars 10.00 o'clock at FA32
Abstract
Novel nano materials with selected properties for high performing,
environmentally friendly fuels and lubricants have recently been
developed. Some of these provide enhanced frictional properties via
unique “ball bearing” type mechanisms due to their spherical shape and
small size. Others rely on interactions with the metal surfaces of
engine parts under pressure to form glassy sacrificial layers via
particle breakdown at the solid steel/liquid interface providing
self-healing mechanisms to improve wear and reduce fuel consumption.
Advanced nano materials like inorganic-fullerenes (IF) used as
additives to oils and greases significantly improve the anti-friction
and anti-wear properties of these lubricants, as the IF treated oils
and greases extensively enhance the performance of all sorts of moving
parts, resulting in large energy savings, less costly equipment
maintenance, improved productivity and reduced pollution.
In order to be able to carry out in-situ tribological studies and to
study the tribo-film formation and possible chemical changes on the
friction exposed surfaces, advanced analytical instruments: TEM, SEM,
FIB, XPS. EDX, EELS instruments are used.
A friction reducing mechanism will be presented and the origin of the
chemical changes will be discussed.
IceCube: Detecting
neutrinos with ns precision within a km3 of ice
by David Nygren
Lawrence Berkeley National Laboratory, California
Thursday the 3rd of April 10.00 o'clock at FA32
Abstract
IceCube is under construction at Antarctica’s South Pole, and is about
half complete. About 1km3 of the deep polar ice will be instrumented
for detection of optical Cerenkov radiation, generated by the charged
products of high energy neutrino interactions. The energy range of
interest spans many decades, from a few tens of GeV up to EeV, adding
dynamic range to the engineering challenges. “Digital Optical Modules”,
organized in a highly decentralized architecture, capture
photomultiplier waveforms with ~1 ns precision. From these signals, the
tracks of high-energy muons can be determined, and, in turn, the
incident direction of the transformed neutrino. Special attention had
to be paid to several engineering issues, and especially to reliability
for electronics operating in an inaccessible and very cold environment.
Measured performance generally meets requirements. A new array,
called “Deep Core” has been recently approved and funded, and will
augment the detection capabilities for the lowest energy muon tracks,
where a WIMP annihilation signal may exist.
Multiparticle entanglement and multiparticle protocols
by Mohamed Bourennane
KoF, SU
Thursday the 29th of May10.00 o'clock at FA32
Abstract
Entanglement is one of the most puzzling features of quantum theory and
of great importance for the new field of quantum information theory.
The determination of whether a given state is entangled or not is one
of the most challenging open problems. For multipartite entangled state
Bell inequalities turned out not to be always suited to distinguish
genuine multipartite entanglement from biseparable, triseparable, etc.
entanglement. Only recently, significant progress in classifying
multipartite entanglement has been achieved using entanglement
witnesses. These observables can always be used to detect entanglement,
when some apriory knowledge about the states under investigation is
provided. It has been shown that witness operators can be implemented
experimentally in a straightforward way by using local projective
measurements, even for multipartite systems. We apply this scheme to
experimentally detect entanglement of multiphoton states. These states
are used for the realization of quantum multiparty communication
protocols such as secret sharing, Byzantine agreement, liar detection,
and tele-cloning.