The history of our group dates back to the 1960's when such pioneers as Timo Paakkari and Pekka Suortti started systematic x-ray crystallographic studies at the Department of Physics (then located near Helsinki downtown, at Siltavuorenpenger). In the 1970's, Seppo Manninen spent a post-doc period at the lab of Prof. Malcolm Cooper, Warwick (UK) and brought the knowhow of x-ray Compton scattering spectroscopy to Helsinki.

SiltavuorenpengerKumpula

Our group's location before and now. Left: Siltavuorenpenger campus (1959-2001).  Right: Kumpula campus (2001- )

Synchrotron radiation

Our group has been utilizing synchrotron radiation already since the 1970's since the work of Pekka Suortti at Brookhaven National Synchrotron Light Source.  He worked with synchrotron radiation techniques including designs of beamlines and their application to spectroscopy, x-ray diffraction, including the resonance phenomena, and medical imaging. In the 1980-1990 period many important researcher visits were made to Daresbury and HASYLAB as well. One important turning point was Keijo Hämäläinen's post-doc period in early 1990's developing inelastic x-ray scattering spectroscopy at Brookhaven's National Synchrotron Light Source under the supervision of Jerry Hastings. Hämäläinen is best known in the field of x-ray spectroscopy from his utilization of resonant x-ray emission spectroscopy to yield much more information on the electronic structure than regular x-ray absorption spectroscopy can yield. The Hämäläinen method was based on the recording of resonant x-ray emission peak intensity when incident photon energy is tuned across an x-ray absorption edge. The variations of the intensity could be interpreted as x-ray absorption spectra with an elimination of the deep core-hole lifetime broadening. Resonant x-ray emission spectroscopy is even nowadays a hypermodern tool for x-ray spectroscopy.

Nowadays we are an integral part of the Finnish Synchrotron Radiation Users' Organization.

Helsinki and light sources

In the end of 1980's Pekka Suortti, amongst others, proposed that Finland should become a member of the then-yet-to-be European Synchrotron Radiation Facility already at its planning phase together with other Nordic countries. At that time there were only few synchrotron radiation users in Finland and it wasn’t clear to many people that it would become such an important research tool for many people worldwide. Currently, roughly 7000 researcher visits are made to ESRF annually.

ESRF is still one of our most important experimental facilities. Annually we perform nearly 10 synchrotron radiation experiments on average, majority of them at ESRF and MAX-Lab.

Helsinki and computational materials physics

Today an important factor of our work is based on the interplay of computational and experimental materials physics. Spectroscopy yields indirect information on the underlying function and structure of materials. Interpretation and prediction of experimental results can only be done through computations. This is an important challenge in our frontier and has been attacked by our group in the early days of our existence. Starting from developing corrections to x-ray powder intensities, calculations of Compon profiles, the interpretation of resonant and non-resonant IXS spectra has been very close to our hearts. One important advance was when J. Aleksi Soininen spent a post-doc period with Eric Shirley (US) in the early 2000's and developed advanced methods to take electron-hole interaction into account in various spectra including valence- and core-excited states. His work includes as well the methodology to extract symmetry-projected densities of states from core-level IXS spectra. Nowadays various kinds of software is routinely used in the group, both locally and at supercomputers, for calculating atomic structures and molecular dynamics, electronic properties, x-ray observables and dielectric properties in general.  

Want to know where we are doing today?

Please visit our Research Topics page.

Happy surfing on our group's pages!

 

 

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