Fundamental Parameters and Metrology

In a world were global challenges like the energy shortage, environmental protection, and economical problems in less developed areas must be addressed, there is a need for new solutions based on sound scientific foundations. Pushing the limits of technology requires a critical assessment and evaluation of available data related to the interactions of radiation with matter that is called “fundamental parameters”. The lack of recent reliable values with low associated uncertainties has been pointed out by the scientific community as well as by industry and metrological laboratories. The research team has addressed this issue considering radiation from the visible and ultra-violet (VUV) to the X-rays and gamma-rays regimes.


Regarding the X-ray regime, the research team has joined the Fundamental Parameters Collaboration that aims to overcome the uneven quality and incompleteness of current X-ray fundamental parameters, and reported recently the most accurate (2.5 ppm), reference-free measurement done for a transition energy value in the X-ray domain. Still in the x-ray radiation analysis field, several members of the research team integrated recently the CREMA (Charge Radius Experiment with Muonic Atoms) collaboration that is going to measure, among others, several transition frequencies between the 2S and the 2P states (Lamb shift) in muonic helium ions, in order to determine the alpha-particle and helion rms.


To overcome the difficulties of the analysis of light elements with X-rays, the research team has acquired also expertise in the proton induced gamma-ray emission (PIGE) and in the VUV electron spectroscopy techniques.


Objectives of this research group are also the study of the physics underlying the decomposition of highly energetic molecules and identification of their reactive intermediates, in particular those relevant to industrial, atmospheric, biological and combustion processes. Photoelectron Spectroscopy, using either He I (21.22 eV) or Synchrotron Radiation in the X-ray range are the techniques used in this project. This work implies design and construction of scientific apparatus, which substantially improve the existing equipment and extend the limits of the experiment. Experimental findings are rationalized using different computational methods to obtain optimized molecular geometries, ionization energies, orbital contours, relative energies, vibrational frequencies, and to assess possible pathways for thermal fragmentation. Synchrotron radiation studies are performed in the 10-35 eV region at the Elettra synchrotron, Trieste, Italy, within a collaborative project with the University of Southampton, UK.and “ La Sapienza”-University of Rome, Italy.