494 research outputs found
Attoscience at ETH Zurich: Shining New Light on Old Questions in Quantum Mechanics
Ten years ago, we began a new research effort in attoscience at ETH Zurich, building on our ultrafast laser expertise in the few femtosecond regime. I present some of the technical highlights and explain how we continue within the NCCR MUST
Sub-cycle time resolution of multi-photon momentum transfer in strong-field ionization
During multi-photon ionization of an atom it is well understood how the
involved photons transfer their energy to the ion and the photoelectron.
However, the transfer of the photon linear momentum is still not fully
understood. Here, we present a time-resolved measurement of linear momentum
transfer along the laser pulse propagation direction. Beyond the limit of the
electric dipole approximation we observe a time-dependent momentum transfer. We
can show that the time-averaged photon radiation pressure picture is not
generally applicable and the linear momentum transfer to the photoelectron
depends on the ionization time within the electromagnetic wave cycle using the
attoclock technique. We can mostly explain the measured linear momentum
transfer within a classical model for a free electron in a laser field.
However, corrections are required due to the interaction of the outgoing
photoelectron with the parent ion and due to the initial momentum when the
electron appears in the continuum. The parent ion interaction induces a
measurable negative attosecond time delay between the appearance in the
continuum of the electron with minimal linear momentum transfer and the point
in time with maximum ionization rate
National Center of Competence in Research: Molecular Ultrafast Science and Technology: Editorial
The Centre for Chemical Sensors/Biosensors and bioAnalytical Chemistry, CCS, at the Interface between Science and the Market Place
In the following article, a very brief overview describing the general strategies and the main goals tackled by CCS is given. The latest news, as well as projects running in collaboration with companies are not discussed here. For more details see homepage, http://www.chemsens.ethz.ch
Development of an optical membrane for humidity
4-(N,N-dioctylamino)-4′-trifluoroacetyl-azobenzene (ETHT 4001), together with the catalyst tridodecylmethylammonium chloride, is dissolved in the hydrophilic polymer polyurethane Tecoflex. The resulting membrane layers show high sensitivity toward water vapour and allow the application of the membranes for humidity measurements. Upon exposure to humid air, the membrane exhibits a decrease in absorbance at a wavelength around 490 nm and an increase at around 430 nm. This signal change is caused by the conversion of the trifluoroacetyl group of the reactand into a diol, thus changing the electron delocalisation of the reactand. The sensor layer exhibits a dynamic range from 1% to 100% RH with highest sensitivity in the 5%-40% RH range. The limit of detection is 0.5% RH. The amount of added catalyst enables the sensitive range to be tailored. The selectivity over ethanol and carbonate is sufficient for the membrane to be used for long-term measurements of air. The change in colour of the humidity-sensitive membrane from red to yellow also means it can be used as an optical test stri
Process Monitoring with Disposable Chemical Sensors Fit in the Framework of Process Analysis Technology (PAT) for Innovative Pharmaceutical Development and Quality Assurance
The innovative principle of enzymatic sensors applied to monitor the feeding process in disposable bioreactors is described. Innovative is the type of enzyme immobilized within the 'paste' to monitor L-glutamate. Innovative is the application of the miniaturized disposable
sensor developed at C-CIT AG for continuous monitoring. The sensor allows the amount of the digested nutrient to be estimated from the amperometric signal. Innovative is the wireless signal transduction between the sensor mounted to the bioreactor and the signal receiver. An example of a process
control run is given and, also, the biocompatibility and the specifications of the biosensors. The comparison of results evaluated by different analytical methods is discussed
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