Polish Academy of Sciences

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Experimental methods
  • Polarisation labelling spectroscopy

The Polarisation Labelling Spectroscopy (PLS) is a powerful method for simplification of complex molecular spectra, which is based on a combination of polarisation spectroscopy and optical double resonance. The basic principle of the PLS is to monitor the change of the polarisation of a weak probe laser beam which is caused  by optical anisotropy of a sample induced by a strong pump beam. In contrary to the classical PLS scheme, this  experiment utilizes a probe laser of fixed frequency, while  the pump laser is scanned over the investigated spectral regions.

  • Thermoluminescence

At temperatures high enough a thermal population of electronically excited molecular states is possible. The elements in metallic form  are loaded to specially built  heat-pipe oven, which construction depends on the types of elements used in the experiment. Atomic vapors are  mixing and reacting in the central part of the heat-pipe, producing molecules. Thermally excited fluorescence spectra may be recorded using  Fourier Transform Spectrometer.

  • Laser induced fluorescence

In laser induced fluorescence (LIF) technique a population of excited states is generated using laser beam, which wavelength is tuned to the known transition between ground and a chosen excited state. We employ a home-made  external-cavity diode lasers whose wavelength is actively stabilized using a High-Finesse WS7 wavemeter. Fluorescence to the ground state is  recorded  with Fourier Transform Spectrometer. Molecules are produced in the heat-pipe oven as during other types of experiments. To increase the contrast between LIF and thermoluminescence signals (observed simultaneously because of high temperature of the heat-pipe oven), the reduction of the temperature of the central part of the heat-pipe is needed.