John G. Conway

Use of Electrodeless Discharge Lamps in the Analysis of Atomic Spectra

The application of electrodeless discharge lamps in obtaining the information necessary for the analysis of the first and second spectra of lanthanide and actinide elements is discussed. It is shown how differentiation of neutral atom and first ion lines, self-reversal, and Zeeman-effect observations may be procured using these lamps as the sole source. The procedures are illustrated by studies on Cm, Gd, and Dy.

Absorption Spectrum of Pu3+ in Lanthanum Trichloride and Lanthanum Ethylsulfate

The polarized absorption spectrum and some Zeeman effect studies were conducted on crystals of lanthanum trichloride and lanthanum ethylsulfate containing 0.1 and 5 mole % of Pu3+ at various low temperatures. The ground‐state levels as well as several excited states are well characterized. Attempts at fitting the positions of levels to 5f hydrogenic free‐ion states give good agreement for F2=245 cm—1 and ζ=2290 cm—1.

Generalized Parametric Study of 5fN and 5fN7s Configurations

The parametric studies of 5fN and 5fN7s configurations by application of both Slater-Condon theory and the generalized least-squares method to the whole sequence of actinides has led to the simultaneous interpretation of 72 levels in first spectra (5fN7s2) and of 112 levels in second spectra (5fN7s). The determination of the N-dependence of various electrostatic parameters of the 5fN core improves the reliability for prediction of missing configurations. Revised interpretations and new energy levels are reported in a number of spectra.

Laser spectroscopy of neptunium; first ionization potential, lifetimes and new high-lying energy levels of Np i

The first ionization potential of neptunium has been determined from the photoionization threshold and from Rydberg series observed by laser spectroscopy techniques. The Rydberg series convergence limits yield the most accurate value of 50 536(4) cm−1 [6.2657(5) eV]. The radiative lifetimes of five levels in the 26 200–29 050-cm−1 range have been measured. New energy levels, 27 odd and 37 even, in the 33 000–37 000-cm−1 range have been determined with approximately ± 0.5-cm−1 precision.

Determination of absolute transition probabilities in neutral cerium from branching ratio and lifetime measurements

We have used the 1-m Fourier-transform spectrometer at the National Solar Observatory, Kitt Peak, Arizona, to record the emission spectrum of 140Ce from an electrodeless discharge lamp in the 4000–27 600-cm−1 range. Branching ratios are determined from the intensity data for transitions originating from common upper levels. These measurements are combined with lifetimes determined by a delayed photoionization technique to yield transition probabilities or gA values for 30 transitions. A plot of the logarithm of intensity divided by gA versus upper energy was constructed; the excitation temperature of the source was determined from this plot. Also from this plot, absolute gA values were derived for 228 of the most intense observed lines of Ce i between 10 706 and 22184 cm−1. To our knowledge, the gA values obtained here are the first reported for neutral cerium.

The emission spectrum of curium

Abstract The curium emission spectrum was observed from 2400 to 11 200 A using electrodeless lamps as sources. Accurately measured wavelengths of 2034 of the strongest 244 Cm lines are reported. The wavelengths, wavenumbers, and relative intensities are given. In addition, Zeeman-effect data, spectrum assignment as neutral or singly ionized lines, isotope shift, and energy-level classifications are given for most of the lines.

Gadolinium enrichment technology at Lawrence Livermore National Laboratory

A method based on polarization selectivity and three step laser photoionization is presented for separation of the odd isotopes of gadolinium. Measurements of the spectroscopic parameters needed to quantify the excitation pathway are discussed. Model results are presented for the efficiency of photoionization. The vapor properties of electron beam vaporized gadolinium are presented which show dramatic cooling during the expansion of the hot dense vapor into a vacuum. This results in a significant increase in the efficiency of conversion of natural feed into enriched product in the AVLIS process. Production of enriched gadolinium for use in commercial power reactors appears to be economically viable using technology in use at LLNL.

The emission spectrum of berkelium

Abstract The berkelium emission spectrum was observed from 2540 to 9800 A with an electrodeless lamp as a source. The wavenumber, wavelength, and relative intensities of the 1930 strongest 249Bk lines are reported. In addition, information on hyperfine structure, Zeeman effect, spectrum assignment as neutral or singly-ionized lines, and energy level classification is presented for many of the lines. Tables of the known energy levels of the neutral and singly-ionized atoms are given.

Revisions and additions to the energy levels of neutral curium (/sup 244/Cm I)

New spectroscopic data obtained using isotopically different samples have led to revisions and additions to the energy levels of neutral curium, 244Cm i. There are now 491 odd and 432 even energy levels with J values. Almost all the levels have isotope shift, and many have g values and configuration designations. Ten odd configurations and nine (one tentative) even configurations have been identified.