A team of researchers from Freiburg led by Prof. Dr. Frank Stienkemeier and
Dr. Lukas Bruder has succeeded in developing a new measurement method for
investigating ultrafast processes in matter. These are processes at the
atomic and molecular level that occur within a billionth of a second (10-12
sec). The new method, which combines different spectroscopy techniques,
enables, among other things, new insights into the energy structure in
matter and the probability distribution of- electrons. Fundamental molecular
processes can now be understood more precisely, according to the
researchers. The results of the research have been published in the
scientific journal Optica and are expected to foster a variety of further
developments in related scientific fields.
Investigating fundamental properties of matter
The Freiburg team has been working for several years on extending ultrafast,
coherent, multidimensional spectroscopy in new directions. Put simply,
spectroscopy involves studying the absorption of light in order to
investigate important properties of matter. These include the mentioned
ultrafast processes, as well as quantum coherence phenomena and interactions
between atoms and other nanoscopic particles. "These are the fundamental
properties of matter that drive the processes in nature at the nanoscopic
level, and we want to better understand these properties through our
experiments," Stienkemeier reports.
A general problem in coherent, multidimensional spectroscopy is the
complexity of the measurement data, which often makes a clear interpretation
of the experimental results difficult or even impossible. The situation
improves significantly when the experiment is combined with the use of, for
example, a mass spectrometer. "This approach gives us the additional and
very useful information about the chemical composition of the substance
under investigation—a major advantage in the study of ultrafast chemical
reactions," Bruder explains.
A host of possibilities
Comparably, the Freiburg researchers have now succeeded in combining
coherent, multidimensional spectroscopy with photoelectron spectroscopy. In
this procedure, the substance is ionized and the energy of released
electrons is measured. This procedure provides information about the energy
structure and spatial probability distribution of electrons (orbitals) in
matter. When photoelectron spectroscopy is combined with X-ray light
sources, precise measurements with atomic selection are even possible,
meaning that the energy distribution in a substance can be studied with
extremely high resolution up to the atomic level.
"Our approach opens up a variety of exciting new developments," Stienkemeier
explains. "This ranges from extending our method for simultaneous energy-
and angle-resolved electron measurements, to experiments with X-rays to
obtain atom-specific information." As another benefit of the Freiburg
approach, the sensitivity of the coherent, multidimensional spectroscopy
experiments has been improved by orders of magnitude. That is, signals that
were previously a factor of 200 smaller than the noise in the measurement
can now be detected. "The increased sensitivity allows us to study very
clean samples in an ultra-high vacuum environment from which we can
understand fundamental molecular processes more precisely," Bruder adds.
Reference:
Daniel Uhl et al, Coherent optical 2D photoelectron spectroscopy, Optica
(2021).
DOI: 10.1364/OPTICA.434853
Tags:
Physics