Ritz Wavelengths Research Articles

Updated System of S i Levels Using Fourier Transform Infrared Spectroscopy in the Range from 800 to 11,000 cm−1

In this study we report on high-precision laboratory measurements of transition wavenumbers for 172 atomic sulfur lines in the infrared region 800–11,000 cm−1 using Fourier transform spectroscopy techniques. Our analysis includes 96 lines that have not been previously measured in the laboratory. We also correct several sulfur energy-level measurements reported in earlier studies. These refined measurements are important for a range of scientific disciplines, such as astrophysics, atmospheric chemistry, and combustion plasma physics. We have used the combined list of all observed lines to derive a refined set of sulfur energy levels. For about half of all nonautoionizing levels, the uncertainties have been reduced by a factor between 2 and 23. From the newly measured nonpenetrating (high-l) Rydberg levels we have also obtained the first ionization energy of the S atom, IE = 83,559.170(11) cm−1, which is more accurate than the currently recommended value by 2 orders of magnitude. Our analysis has led to a significantly more accurate result than the earlier set of Ritz wavelengths with observed intensities reduced to a common uniform scale and an extended list of recommended transition probabilities.

Isotopic shifts in 3 P states of the carbon atom

ABSTRACT Isotope shifts in the transition energies between several lowest 3 P e states of the carbon atom are calculated at the nonrelativistic level of theory. We considered the 12 C, 13 C, and 14 C isotopes, for which we performed variational calculations by expanding the wave functions of the atomic states in terms of all-electron explicitly correlated Gaussian functions. The Born–Oppenheimer approximation was not assumed in the calculations. By combining the computed isotope shifts with the experimentally derived Ritz wavelengths for the natural mixture of the isotopes we make predictions of the positions of the spectral lines for specific carbon isotopes. These predictions may be useful for guiding future experimental measurements of these lines using high-resolution spectroscopy.

Energy Levels and Transition Data of Cs VI

Previously reported atomic data (spectral lines, wavelengths, energy levels, and transition probabilities) were collected and systematically analyzed for Cs VI. The present theoretical analysis was supported by extensive calculations made for Cs VI with a pseudo-relativistic Hartree–Fock (HFR) method together with the superposition of configuration interactions implemented in Cowan’s codes. In this work, all previously reported energy levels and their (allowed) transition assignments were confirmed. A critically evaluated set of optimized energy levels with their uncertainties, observed and Ritz wavelengths along with their uncertainties, and theoretical transition probabilities with their estimated uncertainties were presented in the compilation. In addition to this, we determined the radiative transition parameters for several forbidden lines within the ground configuration 5s25p2 of Cs VI.

Critically Evaluated Atomic Data for the Au iv Spectrum

A spectral investigation of triply ionized gold (Au iv) has been carried out in the wavelength region of 500–2106 Å. The gold spectra were photographed at the National Institute of Standards and Technology, USA, on a 10.7 m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3 m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Our analysis is theoretically supported by the pseudorelativistic Hartree–Fock (HFR) formalism with a superposition of configuration interactions implemented in Cowan's suite of codes. Radiative transition parameters are also calculated using the HFR+CPOL (core polarization effects) model and the multiconfiguration Dirac–Hartree–Fock approach, and their comparisons are used to evaluate the transition rate data. All the previously reported levels of the 5d 8, 5d 76s, and 5d 76p configurations are confirmed, except one, and three are newly established. The missing 1 S 0 level of 5d 8 is now established at 55,277.8 cm−1. A total of 981 observed lines (E1 type), classified to 1031 transitions, including 133 newly identified, enabled us to optimize 139 energy levels. Several astrophysically important transitions, forbidden (M1- and E2-type) lines of 5d 8 and 5d 76s, are provided with their Ritz wavelengths and radiative parameters. A critically evaluated set of energy levels, observed and Ritz wavelengths along with their uncertainties, transition rates, and uniformly scaled intensities of Au iv lines have been presented. Also, large-scale atomic data to compute the opacity of Au iv in the kilonova ejecta have been supplemented in this work.

New Ritz wavelengths and transition probabilities for parity-forbidden, singly ionized nickel [Ni ii] lines of astrophysical interest

ABSTRACT We report accurate Ritz wavelengths for parity-forbidden [Ni ii] transitions, derived from energy levels determined using high-resolution Fourier transform spectroscopy. Transitions between the 18 lowest Ni ii energy levels of even-parity produced Ritz wavelengths for 126 parity-forbidden lines. Uncertainties for the Ritz wavelengths derived in this work are up to two orders of magnitude lower than previously published values. Transition probabilities were calculated using the semi-empirical orthogonal operator method, with uncertainties ranging from approximately 1 per cent for strong M1 lines and up to 10 per cent for weak E2 lines. Accurate forbidden line wavelengths and transition probabilities, particularly for lines in the infrared, are important in the analyses of low-density astrophysical plasmas, such as supernova remnants, planetary nebulae, and active galactic nuclei.

Energy levels, wavelengths and radiative rates for transitions in Hg-like Bismuth

The fourth spectrum of bismuth (Bi IV) has been investigated in the vacuum ultraviolet region. Recordings of bismuth spectra were made on a 3-m normal incidence vacuum spectrograph at Antigonish laboratory in Canada using a triggered spark light source. The theoretical interpretation for this spectrum was made with the pseudo-relativistic Hartree-Fock approach implemented in Cowan's code. The previous analysis of the energy level structure of Bi IV is confirmed and extended with the identifications of the 6p2 1S0 and 5d96s26p 3D2 levels, which were not reported earlier. Two new doubly excited configurations 6p6d and 6p7s were studied for the first time with the identification of 56 spectral lines. In total, 84 energy levels were located in the 5d10[6s2+ 6snp (n = 6, 7) + 6p2 + 6snd (n = 6, 7) + 6s5f], 6p6d, 6p7s, 5d96s2np (n = 6–10) and 5d96s2nf (n = 5–13) configurations, among which fifteen were newly established. A total of 552 spectral lines have now been classified in Bi IV in the region 193–5000 Å. We also present the optimized energy level values, transition rates and Ritz wavelengths along with their uncertainties evaluated using the least-squares fitting procedure.

Energy structure investigations in triply ionized mercury: Hg IV

We report energy level structure of triply ionized mercury (Hg IV). The spectrum was recorded on a 3-m normal incidence vacuum spectrograph in the wavelength region 300 – 2000 Å, using a triggered spark source at the spectroscopy laboratory, St. Francis Xavier University, Antigonish in Canada. Wavelength measurement and the corresponding uncertainties caused by calibration procedures are carefully analyzed. Based on the analysis of original measurements, the energy levels are optimized, which resulted in an improved set of energy level values. A complete disentanglement of the origin of these energy levels may well be impossible; therefore, new configurations have been extended in our theoretical calculations using Cowan's pseudo-relativistic Hartree-Fock code with superposition of interacting configurations. All preceding results were confirmed, and the 5d8(6d + 7s) mixed configurations have been newly established with the aid of experimental data supported by theoretical calculations. Along with the optimized energy eigenvalues, the observed and Ritz wavelengths, transition rates, and eigenvector compositions of Hg IV are also given. The energy level values were optimized using a computer code LOPT.

New Ritz Wavelengths and Transition Probabilities of Parity-forbidden [Mn II] Lines of Astrophysical Interest.

We report a comprehensive list of accurate Ritz wavelengths and calculated transition probabilities for parity-forbidden [Mn II] lines. Ritz wavelengths have been derived from experimentally established energy level values resulting from an extensive analysis of a high-resolution Fourier-transform emission spectrum of singly ionized manganese. Our analysis includes transitions between all known metastable and other long-lived levels of Mn II giving a total of 1130 [Mn II] Ritz wavelengths. Our entire list of derived Ritz wavelengths for [Mn II] lines ranges between 237 nm and 170 μm (42,125-58 cm-1). The accurate Ritz wavelengths and calculated transition probabilities for forbidden lines in this paper are useful in the study and diagnostics of nebulae and other low-density astrophysical plasmas.

Reference wavelengths of Si ii, C ii, Fe i, and Ni ii for quasar absorption spectroscopy.

Wavelengths of absorption lines in the spectra of galaxies along the line of sight to distant quasars can be used to probe the variablility of the fine structure constant, α, at high redshifts, provided that the laboratory wavelengths are known to better than 6 parts in 108, corresponding to a radial velocity of ≈20 ms-1. For several lines of Si ii, C ii, Fe i, and Ni ii, previously published wavelengths are inadequate for this purpose. Improved wavelengths for these lines were derived by re-analysing archival Fourier transform (FT) spectra of iron hollow cathode lamps (HCL), a silicon carbide Penning discharge lamp, and with new spectra of nickel HCLs. By reoptimizing the energy levels of Fe i, the absolute uncertainty of 13 resonance lines has been reduced by over a factor of 2. A similar analysis for Si ii gives improved values for 45 lines with wavelength uncertainties over an order of magnitude scer than previous measurements. Improved wavelengths for eight lines of Ni ii were measured and Ritz wavelengths from optimized energy levels determined for an additional three lines at shorter wavelengths. Three lines of C ii near 135 nm were observed using FT spectroscopy and the wavelengths confirm previous measurements.

Critically evaluated energy levels, wavelengths, transition probabilities, and intensities of six-times ionized cesium: Cs VII

Previously reported works on the spectrum of Cs VII are critically studied using supplementary spectrograms recorded on a 3-m normal incidence vacuum spectrograph in the wavelength region 300–1240 Å at the Antigonish laboratory (Canada). We confirmed the results of the earlier work of Gayasov and Joshi on this spectrum. Our analysis is supported by extended calculations with the pseudo-relativistic Hartree-Fock (HFR) method with superposition of configuration interactions implemented in Cowan's suite of codes. In this critical evaluation, in addition to the accurate energy levels of Cs VII with their uncertainties, observed and Ritz wavelengths with uncertainties and transition probabilities, the uniformly-scaled intensities of Cs VII lines are also presented. A total of 196 lines attributed to 197 transitions enabled us to optimize the energy values of 72 levels in Cs VII spectrum. Furthermore, Ritz wavelengths of 141 possibly observable lines are provided along with their transition probabilities.

Spectra of Ni V and Fe V in the Vacuum Ultraviolet.

This work presents 97 remeasured Fe V wavelengths (1200-1600 Å) and 123 remeasured Ni V wavelengths (1200-1400 Å) with uncertainties of approximately 2 mÅ. An additional 67 remeasured Fe V wavelengths and 72 remeasured Ni V wavelengths with uncertainties greater than 2 mÅ are also reported. A systematic calibration error is also identified in the previous Ni V wavelengths and is corrected in this work. Furthermore, a new energy level optimization of Ni V is presented that includes level values as well as Ritz wavelengths. This work improves upon the available data used for observations of quadruply ionized nickel (Ni V) in white dwarf stars. This compilation is specifically targeted toward observations of the G191-B2B white dwarf spectrum that has been used to test for variations in the fine structure constant, , in the presence of strong gravitational fields. The laboratory wavelengths for these ions were thought to be the cause of inconsistent conclusions regarding the variation limit of as observed through the white dwarf spectrum. These inconsistencies can now be addressed with the improved laboratory data presented here.

A search for the space-time variations in the proton-to-electron mass ratio using the [Fe II] transitions

A new limit in the spatial and temporal variations in the proton-to-electron mass ratio (Δμ/μ) was found from an analysis of the combined 27 Ritz wavelengths of [Fe II] lines found in the quasar spectra together with laboratory data. The obtained result was Δμ/μ=(0.025±0.262)×10−7. This will allow us to check for the space-time variation limits of Δμ/μ over cosmic timescales and develop future improvements in this limit with high redshifts of quasi-stellar objects (QSOs).

An Updated Constraint on Variations of the Fine-Structure Constant Using Wavelengths of Fe II Absorption Line Multiplets

A new stringent limit relating to the variation of the fine-structure constant ( α = e 2 4 π ε 0 ℏ c ) has been extracted from Ritz wavelengths of 27 quasi_stellar object (QSO) absorption spectra lines of Fe II. The calculation was combined with laboratory wavelengths and QSO spectra to obtain the result Δ α / α = ( 0.027 ± 0.832 ) × 10 − 6 . This result suggests how dedicated astrophysical estimations can improve these limits in the future and can also constrain space_time variations.

Improved documentation of spectral lines for inductively coupled plasma emission spectrometry

An approach to improving the documentation of weak spectral lines falling near the prominent analytical lines used in inductively coupled plasma optical emission spectrometry (ICP-OES) is described. Measurements of ICP emission spectra in the regions around several hundred prominent lines, using concentrated solutions (up to 1% w/v) of some 70 elements, and comparison of the observed spectra with both recent published work and with the output of a computer program that allows calculation of transitions between the known energy levels, show that major improvements can be made in the coverage of spectral atlases for ICP-OES, with respect to “classical” line tables. It is argued that the atomic spectral data (wavelengths, energy levels) required for the reliable identification and documentation of a large majority of the weak interfering lines of the elements detectable by ICP-OES now exist, except for most of the observed lines of the lanthanide elements. In support of this argument, examples are provided from a detailed analysis of a spectral window centered on the prominent Pb II 220.353 nm line, and from a selected line-rich spectrum (W). Shortcomings in existing analyses are illustrated with reference to selected spectral interferences due to Zr. This approach has been used to expand the spectral-line library used in commercial ICP-ES instruments (Agilent 700-ES/5100-ES). The precision of wavelength measurements is evaluated in terms of the shot-noise limit, while the absolute accuracy of wavelength measurement is characterised through comparison with a small set of precise Ritz wavelengths for Sb I, and illustrated through the identification of Zr III lines; it is further shown that fractional-pixel absolute wavelength accuracies can be achieved. Finally, problems with the wavelengths and classifications of certain Au I lines are discussed.

Critically Evaluated Energy Levels, Spectral Lines, Transition Probabilities, and Intensities of Neutral Vanadium (V i)

The energy levels, observed spectral lines, and transition probabilities of the neutral vanadium atom, V i, have been compiled. Also included are values for some forbidden lines that may be of interest to the astrophysical community. Experimental Lande g-factors and leading percentage compositions for the levels are included where available, as well as wavelengths calculated from the energy levels (Ritz wavelengths). Wavelengths are reported for 3985 transitions, and 549 energy levels are determined. The observed relative intensities normalized to a common scale are provided.

Critically Evaluated Energy Levels, Spectral Lines, Transition Probabilities, and Intensities of Singly Ionized Vanadium (V ii)

Abstract The energy levels, observed spectral lines, and transition probabilities of singly ionized vanadium, V ii, have been compiled. The experimentally derived energy levels belong to the configurations 3d 4, 3d 3 ns (n = 4, 5, 6), 3d 3 np, and 3d 3 nd (n = 4, 5), 3d 34f, 3d 24s 2, and 3d 24s4p. Also included are values for some forbidden lines that may be of interest to the astrophysical community. Experimental Landé g-factors and leading percentages for the levels are included when available, as well as Ritz wavelengths calculated from the energy levels. Wavelengths and transition probabilities are reported for 3568 and 1896 transitions, respectively. From the list of observed wavelengths, 407 energy levels are determined. The observed intensities, normalized to a common scale, are provided. From the newly optimized energy levels, a revised value for the ionization energy is derived, 118,030(60) cm−1, corresponding to 14.634(7) eV. This is 130 cm−1 higher than the previously recommended value from Iglesias et al.

THE SPECTRUM AND TERM ANALYSIS OF CO iii MEASURED USING FOURIER TRANSFORM AND GRATING SPECTROSCOPY

ABSTRACT The spectrum of Co iii has been recorded in the region 1562–2564 Å (64,000 cm−1–39,000 cm−1) by Fourier transform (FT) spectroscopy, and in the region 1317–2500 Å (164,000 cm−1–40,000 cm−1) using a 10.7 m grating spectrograph with phosphor image plate detectors. The spectrum was excited in a cobalt–neon Penning discharge lamp. We classified 514 Co iii lines measured using FT spectroscopy, the strongest having wavenumber uncertainties approaching 0.004 cm−1 (approximately 0.2 mÅ at 2000 Å, or 1 part in 107), and 240 lines measured with grating spectroscopy with uncertainties between 5 and 10 mÅ. The wavelength calibration of 790 lines of Raassen & Ortí Ortin and 87 lines from Shenstone has been revised and combined with our measurements to optimize the values of all but one of the 288 previously reported energy levels. Order of magnitude reductions in uncertainty for almost two-thirds of the 3d64s and almost half of the 3d64p revised energy levels are obtained. Ritz wavelengths have been calculated for an additional 100 forbidden lines. Eigenvector percentage compositions for the energy levels and predicted oscillator strengths have been calculated using the Cowan code.

ENERGY LEVELS AND SPECTRAL LINES OF QUADRUPLY IONIZED IRON (Fe V)

This paper, combining a critical compilation with new calculations, provides revised comprehensive lists of recommended energy levels, observed spectral lines, and transition probabilities in the spectrum of quadruply ionized iron (Fe V). The new level optimization made in this work is based on critically assessed uncertainties of about 2000 wavelengths previously measured with grating spectrographs. For 80% of energy levels, relative uncertainties have been reduced by a factor of three on average, compared with previously reported uncertainties. For 65% of observed lines, uncertainties of the new Ritz wavelengths are smaller than those of observed wavelengths by a factor of four on average.

THE SPECTRUM OF THORIUM FROM 250 nm TO 5500 nm: RITZ WAVELENGTHS AND OPTIMIZED ENERGY LEVELS

We have made precise observations of a thorium-argon hollow cathode lamp emission spectrum in the region between 350 nm and 1175 nm using a high-resolution Fourier transform spectrometer. Our measurements are combined with results from seven previously published thorium line lists (Giacchetti et al. 1974; Zalubas & Corliss 1974; Zalubas 1976; Palmer & Engleman 1983; Engleman et al. 2003; Lovis & Pepe 2007; Kerber et al. 2008) to re-optimize the energy levels of neutral, singly-, and doubly-ionized thorium (Th I, Th II, and Th III). Using the optimized level values, we calculate accurate Ritz wavelengths for 19874 thorium lines between 250 nm and 5500 nm (40000 1/cm to 1800 1/cm). We have also found 102 new thorium energy levels. A systematic analysis of previous measurements in light of our new results allows us to identify and propose corrections for systematic errors in Palmer & Engleman (1983) and typographical errors and incorrect classifications in Kerber et al. (2008). We also found a large scatter in the thorium line list of Lovis & Pepe (2007). We anticipate that our Ritz wavelengths will lead to improved measurement accuracy for current and future spectrographs that make use of thorium-argon or thorium-neon lamps as calibration standards.

ACCURATE RITZ WAVELENGTHS OF PARITY-FORBIDDEN [Co II] AND [V II] LINES OF ASTROPHYSICAL INTEREST

We report a comprehensive list of accurate Ritz wavelengths for parity-forbidden [Co II] and [V II] lines obtained from the analysis of energy levels measured in the laboratory with Fourier transform emission spectroscopy. Such lines, particularly those in the infrared, are in demand for the analysis of low-density astrophysical plasmas in and around objects such as planetary nebulae, star-forming regions, and active galactic nuclei. Transitions between all known metastable levels of Co II and V II are included in our analysis, producing wavelengths for 1477 [V II] lines and 782 [Co II] lines. Of these, 170 [V II] lines and 171 [Co II] lines arise from transitions with calculated transition probabilities greater than 1 × 10–2 s–1 and upper level excitations of less than 5 eV, and thus are likely to be observed in astrophysical spectra.