ElectronNuclear Double Resonance, Nuclear Moments, and <r^{3}> of Neodymium143 (III) and Neodymium145 (III) in Lanthanum Trichloride
Abstract
The electronnuclear double resonance (ENDOR) spectra of dilute solutions of trivalent Nd^{143} and Nd^{145} ions occurring at the La^{+3} ion sites in the axially symmetric LaCl_{3} structure have been measured at the temperature of boiling He. For laboratory fields of ~ 10^{3} G the frequencies ν_{n} of the ENDOR transitions are in the range 10<=ν_{n}<=1000 Mc sec^{1}. The experimental results for each nuclide have been summarized by giving values of the parameters in the spin Hamiltonian, H_{s}=βH.g.S+S.T'.I+P'[I_{z}^{2}13I(I+1)] β_{n}H.g_{n}'.I, which produce a rigorous leastsquares fit to the data for the two experimental conditions H ⊥ c and H∥c, where c is a vector parallel to the hexagonal axis of symmetry of the LaCl_{3} crystal. The frequencies were fitted with rms deviations of 0.08δ for H∥c and 0.3δ for H ⊥ c, where δ is the average ENDOR line width, 3×10^{5} cps. The g_{n}' factor in the spin Hamiltonian was found to be anisotropic, with g_{nII}'g_{n⊥}'=0.62. A comprehensive theoretical interpretation of the spin Hamiltonian parameters using eigenvectors precisely calculated from the best available crystal field interaction parameters yielded μ(Nd^{143})μ(Nd^{145})=+1.60883+/0.00004, μ(Nd^{143})=1.079+/0.06 nuclear magneton, μ(Nd^{145})=0.671+/0.04 nuclear magneton, Q(Nd^{143})Q(Nd^{145})=+1.96+/0.2, Q(Nd^{143})=(+0.0206+/0.003)×10^{24} cm^{2}, Q(Nd^{145})=(+0.0105+/0.002)×10^{24} cm^{2}, <r^{ 3}(Nd^{+3}, 4f^{3})>=(36.9+/4.5)×10^{24} cm^{3}. An upper limit of one part in two thousand was established for the contribution, if any, of a contact term to the hyperfine interaction. The errors quoted are estimated standard deviations of the mean based upon internal consistency. A discussion of the errors and their sources is given. In particular, the precision of the determination of the nuclear moments μ and Q, of <r^{3}>, and of the contact term was limited mainly by the inaccuracies of the best available values of the crystal field parameters A_{n}^{m}<r^{n}>. Numerical values of the spin Hamiltonian parameters, crystal field eigenvectors, and relevant interaction multiplicative factors are tabulated.
 Publication:

Physical Review
 Pub Date:
 September 1962
 DOI:
 10.1103/PhysRev.127.1940
 Bibcode:
 1962PhRv..127.1940H