Excitation energy moderate pumping

Two-color pump-probe absorption spectroscopy is carried out with moderate pump energies producing small depletions of the vibrational ground state of only a few percent in order to avoid secondary excitation steps and minimize the temperature increase of the sample due to the deposited pump energy. 

In the excitation spectrum of europium (Fig. 6), there is a moderately strong peak at 532 nm, which is also where the fluorescence maximum of uranium exists (Fig. 7). This overlap provides a convenient opportunity for energy transfer between uranium and europium. Codoped silica gel was prepared with a Eu/U ratio of 20 1 [35]. The excitation spectrum for the 615 nm europium emission is shown in Fig. 8 for the codoped samples. For samples with the same europium content, the fluorescence emission is nearly doubled when sensitized by uranium at ideal pumping wavelengths [35]. At nonideal pumping... 

Example 8.1 For saturation of the pump transition even moderate intensities ( p < 10 kW/cm ) are sufficient (Sect. 2.1). Assume an output power of 50 kW of the transfer laser L2 and a beam diameter of 1 mm in the focal plane, which yields /transf = 6.7 MW/cm, energy transfer cross sections of ctt 1.3 X 10 cm, which is about 1000 times larger than the gas-kinetic cross section. The energy transfer Rj = anvhvj, where n is the density of collision partners, colliding with the excited atoms. With n = 10 cm, v = 10 cm/s and hvj = 2 eV, we obtain Rj = l(f eV/s. 

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