OPTICAL MEASUREMENT OF THE ISOTOPE SHIFTS AND HYPERFINE AND SUPERHYPERFINE INTERACTIONS OF ND IN THE SOLID-STATE

We report the observation of optically resolved isotope, hyperfine, an d superhyperfine structure in the spectrum of Nd3+ ions in YLiF4, isot opically pure in Li-7. This observation was made on the (4f(3)-4f(3)), I-4(9/2)(1)-->F-4(3/2)(1) transition of Nd3+ ions present as impuriti es at ppm levels. The optical linewidths of the transitions of the eve n mass number isotopes, Nd-142, Nd-144, Nd-146, Nd-148, and Nd-150, ar e only 45 MHz which makes it very easy to resolve the isotope shift of 115 MHz/unit mass. The hyperfine structure of the two odd mass number isotopes, Nd-143 and Nd-145, are resolved and the hyperfine parameter s are determined in both the ground and electronically excited states. Some of the transitions have linewidths as narrow as 10 MHz. These ar e the narrowest optical inhomogeneous linewidths observed in solids. I n addition, each even isotope line is split by 30 MHz. The observed sp litting is assigned to a superhyperfine coupling between Nd3+ and its nearest-neighbor fluorine nuclei. Here, a superhyperfine splitting has been resolved in an optical spectrum. The optical line shapes for the even isotopes are calculated as the sum of all transitions between th e superhyperfine components (Nd3+ With its eight nearest-neighbor F nu clei) of the ground and excited electronic states, considering both ma gnetic dipole-dipole (including spin-transfer contributions) and conta ct interactions. The results are in quantitative agreement with experi ment.