Cross-relaxation energy transfer

Fig. 15. (A) Energy levels of Nd in LaF3. (B) Cross-relaxation energy transfer leading to concentration quenching in this material...

All glass lasers developed to date have used a rare earth as the active ion and optical pumping for excitation (Stokowski, 1982). Of these, flash-lamp-pumped neodymium glass lasers are the most frequently used and the most widely investigated. The spectroscopic data needed for estimation of the laser characteristics are usually obtained from small samples (Reisfeld and Jprgensen, 1977). The data include absorption, emission, nonradiative relaxation, energy transfer probabilities and laser cross sections. Laser operation predictions can be made from such data without actually demonstrating laser action. 

Figure C3.5.5. Vibronic relaxation time constants for B- and C-state emitting sites of XeF in solid Ar for different vibrational quantum numbers v, from [25]. Vibronic energy relaxation is complicated by electronic crossings caused by energy transfer between sites.

Jameson C. J., Jameson A. K., Smith N. C. 15N spin-relaxation studies of N2 in buffer gases. Cross-sections for molecular reorientation and rotational energy transfer, J. Chem. Phys. 86, 6833-8 (1987). 

Similar results were obtained by De Shazer using a different detection technique, where laser oscillations in the sample were forced to develop from the narrow-band radiation, injected from a second small aperture laser into the sample laser cavity. The interionic transfer allowed the feeding of this narrow-band radiation by ions having frequencies outside this interval. The effeciency of energy extraction within the narrow bandwidth and the degree of depolarization of the laser oscillations parametrize the cross relaxation effects. 

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