NMR measurement of an ion in an excited state by indirect optical detection: AG41level ofLiYF4:Pr3+

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Abstract
NMR measurements of the G41 excited level (9700 cm−1) of trivalent praseodymium in lithium-yttrium fluoride are reported. They were made by indirect optical nuclear double resonance, where a narrow-band optical excitation, which connects the H43 ground state to the D21 excited state (16 741.5 cm−1), pumps individual hyperfine levels. This produces a large polarization of the hyperfine levels, which is preserved as the excitation cascades to the lower crystal-field-split levels. A rf magnetic field induces transitions between the hf states of the longest-lived level (the lowest G41), which are observed through changes in the fluorescence from the lowest D21 level to the ground H43 multiplet. The results may be summarized as parameters in a Hamiltonian: D=+1.000±0.001 MHz, E<0.010 MHz, γz=+2.64±0.02 kHz/G. From these measurements, the hyperfine constant AJ for the G41 states is determined to be 716±30 MHz. Together with data previously reported for the D21 and H43 states, the interaction between the Pr3+ nuclear quadrupole moment and the lattice electric field gradient Platt=0.60±0.04 MHz, and the interaction between the 4f electrons and the nuclear quadrupole moment are given by P4f=0.814±0.010 MHz for H43, 0.028±0.020 MHz for G41, and 2.027±0.030 MHz for