Clyde A. Morrison

Crystal‐field analysis of triply ionized rare earth ions in lanthanum trifluoride

Previously reported spectra of nine triply ionized lanthanides in LaF3 are analyzed by using a parametrized C2 crystal‐field Hamiltonian. Initial crystal‐field parameters Bnm in the fitting procedure were obtained from point charge lattice sums Anm using previously derived ρn, where Bnm=ρnAnm. The largest rms deviation of theory from experiment was 18.1 cm−1 (Pr3+), and the smallest was 2.1 cm−1 (Ho3+). The resulting Bnm were used to obtain a smoothed set of crystal field parameters for the entire lanthanide series whose largest rms deviation was 20.8 cm−1 (Pr3+) and whose smallest was 3.5 cm−1 (Ho3+).

Crystal‐field analysis of triply ionized lanthanides in Cs2NaLnCl6

Optical spectra of the elpasolite hexachloride compounds Cs2NaLnCl6, where Ln represents one of the lanthanide ions, are analyzed with a crystal‐field Hamiltonian of Oh symmetry. Crystal‐field parameters, Bnm, are found that minimize the rms deviation between calculated and experimental energy levels for Ln=Ce, Pr, Nd, Eu, and Tb. A set of ’’smoothed’’ Bnm is found for the lanthanide series that predicts the spectroscopic properties of the remaining eight lanthanide ions. Predicted energy levels and g values are compared with available experimental data for all the lanthanides except Pm and Gd, and magnetic dipole intensities are computed.

Crystal‐field analysis of triply ionized rare earth ions in lanthanum trifluoride. II. Intensity calculations

Implementation of the Judd–Ofelt theory of induced electric dipole transitions is considered for rare‐earth ions in LaF3. Parameters in the theory are derived a priori. Calculations of the multiplet‐to‐multiplet line strengths, lifetimes, branching ratios, and line‐to‐line squared matrix elements are performed between all the energy levels considered for the triply ionized lanthanides Ce3+ through Yb3+. Magnetic dipole calculations are also performed. The g factors for all the lanthanides with an odd number of f electrons are given. Calculated Judd–Ofelt intensity parameters and radiative lifetimes compare reasonably well with experiment.

Optical spectra, energy levels, and crystal‐field analysis of tripositive rare‐earth ions in Y2O3. IV. C3i sites

We report an analysis of new and previously existing optical absorption and fluorescence data, far‐infrared data, and electronic Raman scattering data for Eu3+, Dy3+, and Er3+ in the C3i sites of Y2O3 and R2O3, where R=a rare earth. Our previous analysis of C2‐site spectra yields an effective point‐charge model for the host lattice that allows initial estimates to be calculated for the C3i‐site crystal‐field parameters Bkm. Best‐fit values of B20, B40, and B43 are obtained for Eu, and best‐fit values of all Bkm allowed by symmetry are obtained for Dy and Er. The best‐fit Bkm are in relatively poor agreement with the model; in particular, B20 has the opposite sign from and B44 is much smaller than the model predictions. From the best‐fit Bkm we obtain phenomenological crystal‐field components Akm, from which we predict Bkm and C3i ‐site energy levels for the ground states of Tb3+, Ho3+, Tm3+, and Yb3+. While the effective point‐charge model is apparently too crude to make accurate, quantitative, a priori p...

Energy levels and crystal quantum states of trivalent holmium in yttrium aluminum garnet

Absorption spectra of Ho3+ ions in yttrium aluminum garnet (Ho3+:YAG) are reported between 2.16 and 0.23 μm at various temperatures between 4 K and room temperature. Laser‐excited excitation spectra and emission spectra from the 5F4 and 5S2 multiplet manifolds to the ground state manifold 5I8 were obtained at 4, 20, and 55 K. The majority of Ho3+ ions substitute for Y3+ ions in sites of D2 point‐group symmetry in the lattice. Over 1000 temperature‐dependent transitions (hot bands) establish 280 experimental Stark levels of the 4u2009fu200910(2S+1LJ) multiplet manifolds. Symmetry labels Γ1, Γ2, Γ3, or Γ4, appropriate to D2 symmetry, have been assigned to Stark levels up to 43u2009000 cm−1. Experimental levels are compared with results obtained from a theoretical calculation. The model Hamiltonian includes Coulombic, spin‐orbit, and interconfiguration interaction terms for the 4u2009fu200910 atomic configuration of Ho3+ and crystal‐field terms in D2 symmetry. The Hamiltonian was diagonalized within the 50 lowest 2S+1LJ manifol...

Resonant level lifetime in GaAs/AlGaAs double‐barrier structures

The lifetime of the lowest quasibound state localized between the barriers of a GaAs/AlGaAs double‐barrier structure is calculated as a function of barrier and well dimensions. The results are consistent with high‐frequency experiments.

Symmetry, selection rules, and energy levels of Pr3+:Y3Al5O12

Abstract Absorption, fluorescence, and site-selective excitation spectra of Pr 3+ : Y 3 Al 5 O 12 are reported between 0.4 and 6.7 μm at several temperatures between 1.6 and 90 K. The complexity of the spectra indicates that Pr 3+ ions occupy several different sites. The most intense spectra, representing the majority of the Pr 3+ ions in dodecahedral lattice sites, are analyzed on the basis of electric-dipole selection rules for D 2 site symmetry. Weak spectra are reported but not analyzed due to the difficulty in assigning levels to a particular site. Analyses of intense spectra establish the symmetry of 17 Γ 1 , 12 Γ 2 , 10 Γ 3 , and 12 Γ 4 Stark levels. These 51 levels are compared with the results of a crystal-field splitting calculation. A Hamiltonian consisting of Coulombic, spin-orbit, and crystal-field (D 2 symmetry) terms was diagonalized for all manifolds of the Pr 3+ (4f 2 ) configuration. The rms deviation between calculated and experimental levels is 11 cm −1 .

The orotron–A free‐electron laser using the Smith‐Purcell effect

A theory of operation of the orotron is described in which the electromagnetic field present in the open resonator of the device bunches the electron beam; this bunching leads to coherent oscillation. Theoretical results at 75 GHz are discussed.

Optical spectra, energy levels, and crystal‐field analysis of tripositive rare‐earth ions in Y2O3. III. Intensities and g values for C2 sites

We report measurements of the oscillator strengths between the Stark‐split ground level and numerous excited Stark levels of Nd3+, Sm3+, Er3+, and Tm3+ in the C2 sites of Y2O3. Experimental results are compared with calculations based on the Judd–Ofelt theory of induced electric‐dipole transitions, which uses the odd‐parity terms in the crystal‐field interaction (determined via an effective point‐charge model). We also compare our theoretical results with previous measurements of manifold‐to‐manifold oscillator strengths, excited‐state lifetimes, and Judd–Ofelt intensity parameters. Magnetic‐dipole contributions to the intensities are included as well. Calculated ground‐state g values for all the rare earths with an odd number of f electrons are reported. Comparison of theoretical and experimental results indicates that good agreement is obtained in most cases.

Analysis of the ground term energy levels for triply ionized neodymium in yttrium orthovanadate

An investigation has been made of the 4I ground term of Nd3+ in YVO4. Wavelength and polarization measurements of the absorptions in the wavelength range 0.8–2.6 μm were used to establish energy levels for the 4F3/2, 4I9/2, 4I13/2, and 4I15/2 multiplets. These data were correlated with reported spectra in the literature, and an energy level scheme was obtained that identifies 25 out of the possible 26 ground term levels. By diagonalizing the Hamiltonian H = J λn (L⋅S)n + J B+km Ckm in an LS basis and performing a least squares calculation, an rms deviation between calculated and experimental energy levels of 4.01 cm−1 was obtained. The parameter values giving this fit are λ1=293.74, λ2=−2.454, λ3=0.0389, B20=−135.7, B40=625.9, B60=−1169.5, B44=1023.9, and B64=−251.4 cm−1. Theoretical values of g∥ = −0.915 and g⊥ = 2.379 are in good agreement with Ranon’s reported values of g∥ = ±0.915 and g⊥ = 2.348 for the ground state; thus the ground state symmetry property was determined to be Γ7,8 in S4 notation or Γ...