This compilation revises the 1991 listing of atomic data for the lighter elements from hydrogen to gallium. The tabulation emphasizes resonance lines, i.e., lines whose lower level is the ground state, or an excited fine-structure state of the ground term, and is restricted to wavelengths longward of the H I Lyman limit at 911.753 ?. All but the very weakest known and predicted electric-dipole transitions are included, but no forbidden lines. This paper has attempted to review all data published by the end of 2002.?????The tables contain the best data available to the author on ionization potentials, level designations, vacuum and air wavelengths, lower and upper energy levels, statistical weights, transition probabilities, natural damping constants (reciprocal lifetimes), oscillator strengths, and the often used combinations of log gf and log ?f. All ion stages with relevant classified lines are included. Individual components resulting from isotope shift and hyperfine structure are listed explicitly for certain species. The accompanying text provides references, explanations for the critical selection of data, and notes indicating where new measurements or calculations are needed.?????This compilation should be particularly useful in the analysis of interstellar and quasar absorption lines and other astrophysical sites where the density of particles and radiation is low enough to excite only the lowest atomic levels. The data also are relevant to the study of stellar atmospheres, and gaseous nebulae.?????An Appendix summarizes new data relevant to the similar compilation in Paper II for the elements germanium to uranium.

https://iopscience.iop.org/article/10.1086/377639/pdf

Atomic Data for Resonance Absorption Lines. III. Wavelengths Longward of the Lyman Limit for the Elements Hydrogen to Gallium

Five simple microwave cavities for producing discharges in gases were tested in He and H2 at pressures from 1 μ to 1 atm. Three of the cavities are commonly used, and two have been recently designed. One of the newly designed cavities offered a considerable improvement over early models with respect to compactness, ease of attachment to the system, and efficiency.

Microwave Discharge Cavities Operating at 2450 MHz

Amplitude variation with offset (AVO) interpretation may be facilitated by crossplotting the AVO intercept (A) and gradient (B). Under a variety of reasonable petrophysical assumptions, brine‐saturated sandstones and shales follow a well‐defined “background” trend in the A-B plane. Generally, A and B are negatively correlated for “background” rocks, but they may be positively correlated at very high VP/VS ratios, such as may occur in very soft shallow sediments. Thus, even fully brine‐saturated shallow events with large reflection coefficients may exhibit large increases in AVO. Deviations from the background trend may be indicative of hydrocarbons or lithologies with anomalous elastic properties. However, in contrast to the common assumptions that gas‐sand amplitude increases with offset, or that the reflection coefficient becomes more negative with increasing offset, gas sands may exhibit a variety of AVO behaviors. A classification of gas sands based on location in the A-B plane, rather than on normal‐...

Framework for AVO gradient and intercept interpretation

This compilation extends the 1991 listing of atomic data by Morton to the heavier stable elements from germanium to bismuth Technetium, thorium, and uranium are added because they can live long enough to be astrophysically detectable The tabulation emphasizes resonance lines, ie, lines the lower level of which is the ground state, or an excited fine-structure state of the ground term, and is restricted to wavelengths longward of the H I Lyman limit at 91175 A This paper has attempted to review all data published by mid-1999 and includes some later material     The tables contain the best data available to the author on level designations, ionization potentials, vacuum and air wavelengths, lower and upper energy levels, statistical weights, transition probabilities, natural damping constants (reciprocal lifetimes), oscillator strengths, and the often-used combinations of log gf and log λf All ion stages with classified lines are included Individual components resulting from isotope shift and hyperfine structure are listed explicitly for Rb I, Cs I, Hg I and Hg II, Ti II, and Pb II The accompanying text provides references, explanations for the critical selection of data, and notes indicating where new measurements or calculations are needed     This compilation should be particularly useful in the analysis of interstellar and quasar absorption lines and other astrophysical sites where the density of particles and radiation is low enough to excite only the lowest atomic levels The data also are relevant to the study of stellar atmospheres, particularly those with enhanced abundances of heavy elements

https://iopscience.iop.org/article/10.1086/317349/pdf

Atomic Data for Resonance Absorption Lines. II. Wavelengths Longward of the Lyman Limit for Heavy Elements

Laser spectroscopy for nuclear structure physics

Photoionization and Rydberg spectra of ten lanthanides have been studied using stepwise laser excitation and ionization methods. These spectra were obtained from several different laser populated excited states in each case. Accurate ionization limits were derived from observed photoionization thresholds. Except for praseodymium, the observation of one or more long Rydberg progressions allowed more accurate limits to be determined. The Rydberg convergence values in eV are: Ce, 5.5387(4); Nd, 5.5250(6); Sm, 5.6437(6); Eu, 5.6704(3); Gd, 6.1502(6); Tb, 5.8639(6); Dy, 5.9390(6); Ho, 6.0216(6), and Er 6.1077(10). For praseodymium a threshold value of 5.464(+12-2) was obtained. When plotted against N, the lanthanide ionization limits normalized to correspond to ionization from the lowest level of fNs2 to the lowest level of fNs form two straight lines connected at the half-filled shell.

/pdf/first-ionization-potentials-of-lanthanides-by-laser-51y63topo8.pdf

First ionization potentials of lanthanides by laser spectroscopy

We report the first observation of perturbed and unperturbed Rydberg progressions of atomic uranium. Highlying levels within 1000 ${\mathrm{cm}}^{\ensuremath{-}1}$ of the ionization limit were accessed by time-resolved stepwise excitation using dye laser pulses tuned to resonant transitions. Atoms excited to these states were then photoionized by intense infrared radiation from a pulsed ${\mathrm{CO}}_{2}$ laser. The resultant photoion production was monitored. By delaying the infrared ionizing pulse, and thus discriminating against the shorter-lived valence states, we preferentially detected Rydberg levels with principal quantum numbers $n$ exceeding 60. Series convergence yields a value of the ionization limit of 6.1941 \ifmmode\pm\else\textpm\fi{} 0.0005 eV, in fair agreement with the value of 6.1912 \ifmmode\pm\else\textpm\fi{} 0.0025 eV obtained in photoionization studies. Ab initio calculations indicate that the unperturbed series belong to highly excited $5{f}^{3}7{s}^{2}\mathrm{np}$ and $\mathrm{nf}$ configurations.

Detection of Rydberg states in atomic uranium using time-resolved stepwise laser photoionization

We report the observation of over 100 new high-lying odd levels in atomic uranium between 32 600 and 34 200 cm−1 using tunable laser techniques. These augment the 32 odd levels previously determined in this energy regime by conventional atomic spectroscopy. The method used in these studies, multistep photoionization under pulsed dye laser excitation, was also employed to make J assignments, measure radiative lifetimes, and to obtain absorption cross sections of transitions involving these levels.

Radiative lifetimes, absorption cross sections, and the observation of new high-lying odd levels of 238 U using multistep laser photoionization*

Accurate wavelengths and wavenumbers of over 22 000 dysprosium lines have been measured in the wavelength region 2300–11 400 A. The Zeeman effect has been observed at a field strength of 24 000 G from 2300 to 9000 A. By comparison of relative intensities of the lines from sources under various conditions, 85% of the lines have been assigned as Dy i or Dy ii spectrum lines. From the energy-level analysis, 141 even and 197 odd levels of Dy i are known. Combinations between these levels account for 1952 lines. For Dy ii, 14 even and 214 odd levels are known, with 1000 lines classified. The ground levels of Dy i and Dy ii are 4f106s25I8 and 4f106s⁶I812, respectively. The lowest level of the 4f95d6s2 configuration of Dy i lies 7565.62 cm−1 above the ground level. The g values for most of the levels of both spectra are given.

/pdf/preliminary-level-analysis-of-the-first-and-second-spectra-59e36wjg0d.pdf

Preliminary Level Analysis of the First and Second Spectra of Dysprosium, Dy I and Dy II

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.

Earl F. Worden

Papers

First ionization potentials of lanthanides by laser spectroscopy

Detection of Rydberg states in atomic uranium using time-resolved stepwise laser photoionization

Radiative lifetimes, absorption cross sections, and the observation of new high-lying odd levels of 238 U using multistep laser photoionization*

Preliminary Level Analysis of the First and Second Spectra of Dysprosium, Dy I and Dy II

Use of electrodeless discharge lamps in the analysis of atomic spectra