INFRARED SPECTROMETRY AT THE ROSSSENDORF FREE ELECTRON LASER - THE PROJECT


OBJECTIVE:

Infrared measuring of low concentration components in liquid (aqueous) and solid environmental samples, determination of the chemical binding of actinides at humic components, at surfaces of minerals and rocks, and in bacteria.

PRESENT SITUATION:

Standard methods of infrared spectroscopy 12,000 - 50 cm-1 (0.8 - 200 µm) at the Perkin-Elmer Mod 2000 FTIR spectrometer:

  • transmission techniques:
    solid samples: different pellet techniques and Nujol method
    aqueous samples: different cuvettes, e.g. CaF2 , AgCl
  • reflection techniques:
    solid samples: diffuse reflection (DRIFT)
    solid and liquid samples: attenuated total reflection (ATR)
  • photo acoustic techniques:
    opaque samples (liquid or solid)

The low intensity of the infrared beam limited the sensitivity of the spectroscopic methods, therefore, low concentration components are not measurable, e. g. complexes of actinides in environmental samples.

PERSPECTIVE: THE FEL - INFRARED LIGHT

Scheme of Free Electron Laser
Principle of the Free Electron Laser (FEL) for infrared light generation.

The intensive, pulsed IR light (middle and far infrared) is generated by a Free Electron Laser (FEL), which is installed at ELBE. The energy is ca. 10 µJ per pulse. Both the wave length and the pulse length are well adjustable, see table below.

wave number
[cm-1]
wave length
[µm]
pulse length
[ps]
2000 - 500 5 - 20 0.3 - 5
670 - 66 15 - 150 1 - 10

EXPERIMENTS:

The Radiochemical FEL-IR-Laboratory (Head: Dr. Harald Foerstendorf) will be designed for working with radioactive elements, especially actinides. The specific feature of the Radiochemical FEL-IR-Laboratory is the investigation of components at extremly low concentrations. The following investigations are scheduled:

  • Sorbed organics at surfaces of minerals and rocks
  • Surface complexes at minerals and rocks
  • Dissolved and colloid components in aqueous phase
  • Imaging and mapping of surfaces
  • Kinetic investigations

The introduction of photo-thermal methods and the sum frequency generation (SFG) for investigations of surfaces ar in the focus of development . Main part of the experimental setup is an inert gas box for experiments under controlled atmosphere, e.g. free of oxygen.

An first experiment using pulsed photo-thermal spectroscopy and based on the proposal "Infrared Microspectrometry of Environmental Samples" started at the CLIO Experiment (FEL facility LURE, Orsay, France) in June 2000 and will be finished in 2003. The Radiochemical FEL-IR Laboratory will be put into operation in 2004, first radioactive experiments with actinides will start in 2005.