Photon-echo nuclear double resonance and its application in ruby

Abstract

A photon-echo nuclear double resonance (PENDOR) experiment which detects nuclear magnetic resonances by monitoring the stimulated photon-echo intensity after the application of an rf pulse is described and used to determine the Cr-Al hyperfine and electric-quadrupole interaction parameters associated with the ${\mathrm{Cr}}^{3+}$ ion in the ${}_{}{}^2{}_{}{}^{}E\left(\overline{E}\right)$ optically excited state in ruby. Most of these parameters are found to be within a few percent of the values associated with ${\mathrm{Cr}}^{3+}$ in the ${}_{}{}^4{}_{}{}^{}A_2^{}{}_{}{}^{}$ ground state. Resonances are also observed associated with the latter, state, and they are in agreement with previous spin-echo ENDOR work. High resolution is obtained by using a gated cw ruby laser which generates a rapid train of three-pulse stimulated-photon echoes with a long time interval between the second and third excitation pulses. The theoretical behavior of the PENDOR effect is discussed with emphasis on the ability to disentangle complicated multiple overlapping resonances by causing whole sets of resonances to disappear in a controlled way.