Rise and decay of pulsed cathodoluminescence in Nd:YAG single crystals and ceramics

The kinetics of pulsed cathodoluminescence of Nd$^{3+}$ ions in Nd:YAG single crystals and ceramic samples was studied. In these substances, luminescence appears after the ending of exposure by an electron beam with a duration of 2 ns. Optical transitions are observed from the $^{2}F_{5/2}$ level and manifest themselves in the ultraviolet and visible regions of the spectrum, and from the $^{4}F_{3/2}$ level – in the near infrared region. The kinetics of luminescence is characterized by a rise and a decay and is described by the difference between two exponential functions. It has been determined that the characteristic decay times of luminescence are the lifetimes of the $^{2}F_{5/2}$ and $^{4}F_{3/2}$ radiative levels, and the time of a rise is determined by the pumping mechanism. Moreover, the pumping of the uppermost Stark component of the $^{2}F_{5/2}$ level occurs in the process of linear recombination of the ionized neodymium ion with free electrons, and the $^{4}F_{3/2}$ level is due to nonradiative transitions from the upper levels.