H. M. Crosswhite

Spectrum analysis of U3+:LaCl3

The spectrum of U3+:LaCl3 has been analyzed; 53 crystal states of electronic origin have been identified, many of them accompanied by extensive vibronic sidebands having a recognizable structure similar to that for lanthanide‐doped LaCl3. Seventeen energy level parameters were varied simultaneously in a least‐squares adjustment yielding a mean error of 26 cm−1. Values for the crystal field parameters are: B20=260±64 cm−1, B40=−532±139 cm−1, B60=−1438±113 cm−1 and B66=1025±88 cm−1.

Energy level analysis of Np3+:LaCl3 and Np3+:LaBr3

The polarized absorption and fluorescence spectra of 0.01–5% Np3+ doped into single‐crystal LaCl3 were measured at moderate and high resolution in the range to 50 000 cm−1 at 298, 77, and 4 K. The 150 crystal field components identified were fit by a parametrized model which has previously been shown to provide an excellent account of the energy level structures observed for lanthanides doped into LaCl3. This constitutes the first successful evaluation of the crystal field interaction for an actinide ion in LaCl3 in which J mixing effects were explicitly included. The crystal field parameters for Np3+:LaCl3, B20=163, B40=−632, B60=−1625, and B66=1028, all in cm−1, were determined to be approximately twice as large as those for the analogous lanthanide, Pm3+:LaCl3. From analysis of Zeeman patterns in the fluorescence spectra, the ground state was found to be doubly degenerate, having crystal quantum numbers ±2 and a parallel splitting factor 0.17 LU (Lorentz unit).

Spin‐correlated crystal field parameters for lanthanide ions substituted into LaCl3

Fits to spectral energy levels for Ho3+:LaCl3 and Gd3+:LaCl3 establish, for the first time, empirical values of the lanthanide spin‐correlated crystal field parameters. The fitted rank 6 parameters are consistent with the superposition model analysis and provide the solution to a long standing problem in the fitted values of the crystal field parameters for trivalent lanthanide ions in LaCl3.

Parametric energy level analysis of Ho3+: LaCl3

A 20‐parameter least‐squares fit to the levels of Ho3+:LaCl3 observed by Dieke and Pandey has been obtained. The results are in substantial agreement with their assignments and with the subsequent analysis of Rajnak and Krupke. A considerably more extensive atomic Hamiltonian was used, including operators for two‐ and three‐particle electrostatic interactions, spin–orbit and spin–other‐orbit magnetic interaction, two‐particle pseudomagnetic configuration‐mixing interactions, and single‐particle crystal‐field interactions. The fit of twenty parameters to 128 observed levels resulted in a mean error of 5.2 cm−1. The results are consistent with similar recent studies of Nd3+ and Pm3+ in the LaCl3 host.

Spectroscopic Properties of the f-Elements in Compounds and Solutions

In this systematic examination of some of the spectroscopic properties of the f-elements we deal with both the trivalent lanthanides and actinides. We summarize the present status of our energy level calculations in single crystal matrices and in aqueous solution, and compare the predicted crystal-field structure in certain low-symmetry sites with that observed. Some interesting new structural insights are thereby gained. The state eigenvectors from these calculations are then used in part in reassessing and interpreting the intensities of transitions in aqueous solution via the Judd-Ofelt theory. The parameters of this theory derived from fitting experimental data are compared with those computed from model considerations. Finally, we discuss some recent contributions to the interpretation of excited state relaxation processes in aqueous solution.

Absorption spectra of NpCl3 and NpBr3

Low temperature absorption spectra are reported for NpCl3 and NpBr3 in the range 3300–40 000 cm−1. Term assignments are made to a number of excited levels not previously identified, and the data are interpreted in terms of a refined free‐ion model. Some of the parameters associated with this model are found to have similar values for both 3+ actinide and lanthanide chlorides. The values determined for other of the parameters are in good agreement with those calculated independently using Hartree‐Fock methods. The similar crystal‐field quantum number ordering of levels in the ground states of actinide trichlorides and analogous lanthanides doped into LaCl3 is noted and discussed.

Fluorescent and dynamic properties of optically excited dysprosium trifluoride

Fluorescent, excitation, and absorption spectra of DyF3 are reported. The energies of the electronic states of the ground level are significantly shifted compared to those of the dilute system DyxLa1−xF3 and are consistent with recent specific heat measurements from 5 to 350 K. The fluorescent decay rate K of the (4F9/2)1 state follows the equation K(μs−1)=1.600+0.0307 T(K), where T(K) is the absolute temperature. At 0 K the quantum efficiency is approximately 4.5×10−4. The decay rate is determined by the donor‐to‐acceptor transfer rate, where an acceptor is a pair of coupled dysprosium ions which deactivate the (4F9/2)1 state. Cross relaxation of the form 4F9/2+6H15/2→6F3/2+6H5/2 is calculated to be the dominant dipole–dipole decay channel. Comparison of high‐resolution absorption line shapes, measured above 4.2 K, and below the ferromagnetic transition 2.53 K shows a shift of the line centers, and a reduction, by a factor of 6 in the linewidths. These results are consistent with analogous measurements p...

Magnetic effects in Ba I and Sr I absorption spectra

Results of high-resolution work on the s21S0-snp 1P01 absorption series of Ba I and Sr I in magnetic fields of up to 4.7 T are reported, with special attention paid to measurement of ‘ quasi-Landau resonances ’ beyond the zero-field limit. Also, the Zeeman patterns of the 6s21S0- 5d8p 3P01, 3D01 transitions are reported, and interpretations are given involving a magnetically forced transition to a level close to 5d8p 3D01.

Simultaneous Diamagnetic and Paschen-Back Effects in Rydberg Series of In(I)

We qualitatively describe magnetic structures in both π- and σ -polarization for In(I) Rydberg series. Two types of shift of Zeeman patterns, proportional to the square of the magnetic field, and ascribable respectively to partial Paschen-Back effect and atomic diamagnetism - previously considered mutually exclusive - are found to occur simultaneously. We attempt quantitative description of this combination.

Evidence for Motional Electric Field Effects in the Absorption Spectrum of Lithium Vapor in a Magnetic Field

Since the discovery, by Garton and Tomkins in 1969 [1], of magnetically-induced periodic fluctuations in the vicinity of the ionization limit in the Ba I absorption spectrum, there has been a growing interest in high-energy spectroscopic phenomena. Developments in fundamental theory, particularly by the Fano school, have opened up new perceptions of the importance of such phenomena to basic physical and chemical processes. Magnetic effects, of course, constitute only a small part of high-energy spectroscopic phenomena; however, a brief review of some of the experimental results, and of the interpretation of these results, is trenchant in defining the place of magnetic effects in the overall high-energy context. Such, indeed, is the purpose of this paper.