K. Čermák's research while affiliated with Instytut Chemii i Techniki Jądrowej and other places
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Publications (6)
The concentration dependence of mean fluorescence lifetimes of chlorophyll a in methanol was studied in the concentration interval 3 × 10−6 − 7.3 × 10−5 mol l−1 at room temperature. The values found experimentally were corrected for reabsorption of fluorescence using the average molar absorptivity F derived from spectral properties of overlapping f...
On exposure to intensive light containing the near UV spectrum region transient colour centres are formed in YAG: Nd. Their optical properties are accounted for by optically induced transfer of the hole arising between O−2 anions in the neighbourhood of the defect within the cation sub-lattice.
Formation of a transient absorption centre is demonstrated in YAG : Nd monocrystals on intensive irradiation in the near UV spectrum region. Spectral distribution has been studied of their absorption coefficient, their decay kinetics was also followed. Activation energy of the decay process was determined from the temperature dependence. The transi...
Luminescence accompanying the disintegration of colour centres formed by the intensive irradiation of the YAG : Nd single crystals with light containing near UV region of the spectrum is studied. Spectral distribution is studied together with the luminescence decay kinetics.
Citations
... The Nd:YAG single crystals are always needed to be annealed in air to reduce the oxygen vacancies that are introduced during growth in reducing atmosphere [12][13][14][15]. Just as in single crystals, there are unavoidable defects in Nd:YAG ceramics after vacuum sintering, which degrade the optical properties significantly. ...
... These bands, as discussed above, are mostly attributed to impurities (e.g. Fe 3+ ), (F + , F, F --centers) or Ocenter [24][25][26][27][28][29][30]. The defect emission from Fe-Fe impurity is responsible for absorption bands at 407 and 415 nm. ...
... Under these conditions, a range of side effects occurs, which undermine the fluorescence data. One of them is photon re-absorption, known to distort the shape of the fluorescence spectrum and consequently to alter the decay-associated components [9][10][11] . Re-absorption by chlorophyll a dissolved in organic solvents at concentrations higher than 1 mM was shown to induce a distortion of the fluorescence lifetimes 12 . ...
... The irradiation of active elements leads to creation of color centers (CC), which can absorb pumping light (passive losses) as well as reabsorb laser radiation (active losses). Depending on lifetime CC in oxide laser crystals can be divided into stable color centers (SCC) existing in crystals in the time range from seconds to a few months or years, and transient color centers (TCC), which lifetime lies in the time range less than one second after the end of excitation [4,5]. SCC usually are responsible for passive energy losses, and TCC -for active energy losses [4,6,7]. ...
... ). τ F is the fluorescence lifetime (τ F~5 ns [3]). c is the speed of light in vacuum and n is the surrounding medium refractive index (n=1.36 ...
Reference: Optofluidic chlorophyll lasers
... The various models that have been proposed indicate the diversity of opinion. Examples include those by Cermak and Linka [10], Mori [11], Bernhardt [12] and Hayes et al [6]. The electron beams used in CL typically only excite the material to a depth of say 1 micron (e.g. for energies of ∼20 keV) thus spectral analysis of luminescence from CL, and also from TL following the electron irradiation, offers data on the imperfections and quality of the near surface layers. ...
