Spin-lattice relaxation time of the relaxed excited state of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>F</mml:mi></mml:math>center in KI and KBr

Abstract

The spin-lattice relaxation time of the relaxed excited state (RES) of the $F$ center in KI and KBr has been measured at 1.85 K and at magnetic fields up to 80 kG. The experimental data can be fitted with the same analytical expression as that used for the ground state, but the relaxation times are about three orders of magnitude smaller than those of the ground state. An attempt to extend to the RES the mechanisms effective in the ground state proved to be unsatisfactory.