Extreme ultraviolet laser excitation of isotopic molecular nitrogen: the dipole-allowed spectrum of ¹⁵N₂ and ¹⁴N¹⁵N

Extreme ultraviolet+ultraviolet (XUV+UV) two-photonionizationspectra of the b ¹Πu(v=0–9), c₃¹Πu(v=0,1), o ¹Πu(v=0,1), c′₄¹Σ⁺u(v=1) and b′¹Σ⁺u(v=1,3–6) states of ¹⁵N₂ were recorded with a resolution of 0.3 cm⁻¹ full-width at half-maximum (FWHM). In addition, the b ¹Πu(v=1,5–7) states of ¹⁴N¹⁵N were investigated with the same laser source. Furthermore, using an ultranarrow bandwidth XUV laser [∼250 MHz (∼0.01 cm⁻¹) FWHM], XUV+UV ionizationspectra of the b ¹Πu(v=0–1,5–7), c₃¹Πu(v=0), o ¹Πu(v=0), c′₄¹Σ⁺u(v=0), and b′¹Σ⁺u(v=1) states of ¹⁵N₂ were recorded in order to better resolve the band-head regions. For ¹⁴N¹⁵N, ultrahigh resolution spectra of the b¹Πu(v=0–1,5–6), c₃¹Πu(v=0), and b′¹Σ⁺u(v=1) states were recorded. Rotational analyses were performed for each band, revealing perturbations arising from the effects of Rydberg-valence interactions in the ¹Πu and ¹Σ⁺u states, and rotational coupling between the ¹Πu and ¹Σ⁺umanifolds. Finally, a comprehensive perturbation model, based on the diabatic-potential representation used previously for ¹⁴N₂, and involving diagonalization of the full interaction matrix for all Rydberg and valence states of ¹Σ⁺u and 1Πu symmetry in the energy window 100 000–110 000 cm⁻¹, was constructed. Term values for ¹⁵N₂ and ¹⁴N¹⁵N computed using this model were found to be in good agreement with experiment.The work was supported by the European Community, under the Access to Research Infrastructures initiative of the Improving Human Potential Program, Contract No. HPRI-CT-1999-00064. K.G.H.B. was supported by the Scientific Visits to Europe Program of the Australian Academy of Science

Probing the Gravitational Dependence of the Fine-Structure Constant from Observations of White Dwarf Stars

Hot white dwarf stars are the ideal probe for a relationship between the fine-structure constant and strong gravitational fields, providing us with an opportunity for a direct observational test. We study a sample of hot white dwarf stars, combining far-UV spectroscopic observations, atomic physics, atmospheric modelling, and fundamental physics in the search for variation in the fine structure constant. This variation manifests as shifts in the observed wavelengths of absorption lines, such as quadruply ionized iron (FeV) and quadruply ionized nickel (NiV), when compared to laboratory wavelengths. Berengut et al. (Phys. Rev. Lett. 2013, 111, 010801) demonstrated the validity of such an analysis using high-resolution Space Telescope Imaging Spectrograph (STIS) spectra of G191-B2B. We have made three important improvements by: (a) using three new independent sets of laboratory wavelengths; (b) analysing a sample of objects; and (c) improving the methodology by incorporating robust techniques from previous studies towards quasars (the Many Multiplet method). A successful detection would be the first direct measurement of a gravitational field effect on a bare constant of nature. Here we describe our approach and present preliminary results from nine objects using both FeV and NiV.This project is funded by a Leverhulme Trust Research Grant. WULTB wishes to acknowledge support from the LABEX Plas@par managed by the French ANR (ANR-11-IDEX-0004-02). J.D. Barrow is supported by the STFC of the UK

Quantum non-adiabatic study of the quasi-molecular satellites of the Lyman line perturbed by H

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Quantum scattering study of the abstraction reaction of H atoms from tetramethylsilane

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Analysis of the spectrum of the (5d6^6+5d5^56s)−(5d5^56p+5d4^46s6p) transitions of two times ionized osmium (Os III)

International audienceThe spectrum of osmium was observed in the (225–2100) Å wavelength region. The (5d 6 + 5d 5 6s) − (5d 5 6p + 5d 4 6s6p) transition array of two times ionized osmium, Os III, has been investigated and 1039 spectral lines have been classified in the region. The analysis has led to the determination of the 5d 6 , 5d 5 6s, 5d 5 6p and 5d 4 6s6p configurations. Fifty-eight levels of the 5d 6 and 5d 5 6s configurations in the even system and 142 levels of the 5d 5 6p and 5d 4 6s6p configurations in the odd system have been established. The orthogonal operators technique was used to calculate the level structure and transition probabilities. The energy parameters have been determined by the least squares fit to the observed levels. Calculated transition probability and energy values, as well as LS -compositions obtained from the fitted parameters are presented

The Spectrum and Term Analysis of Singly Ionized Manganese

International audienceAn extensive analysis of the Mn spectrum was carried out using high-resolution Fourier transform (FT) and grating spectroscopy of Mn-Ne and Mn-Ar hollow cathode discharge sources, over the range 82-5500 nm (1820-121,728 cm-1). Spectral wavelengths for a total of 6019 Mn II lines have been measured, of which 1345 are obtained through FT spectroscopy. These wavelengths are given to at least an order of magnitude lower uncertainty than previous measurements. These lines were used to identify 6256 Mn II transitions and improve the values of 505 previously published energy levels with typical uncertainties of a few thousandths of a cm-1, representing an order-of-magnitude reduction in uncertainty. We have verified and improved an additional 57 Mn II energy levels, previously established through observation of stellar spectra alone, using our FT spectra. In addition, 52 new energy level values have been established. The number of classified lines reported is approximately 50% more than previously published. The new accurate data for 614 energy levels and 6019 lines will allow a more reliable analysis of Mn II spectral lines in astrophysical spectra

Observation and interpretation of the Tm

The emission spectrum of thulium produced by a vacuum spark source was observed in the wavelength range from 700 to 2320 Å  on the 10.7 m normal-incidence vacuum ultraviolet spectrograph at the Paris-Meudon observatory. In the unknown spectrum of Tm IV, more than 760 lines have been identified for the first time as transitions between 157 levels of 4f115d, 33 levels of 4f116p, 9 levels of 4f116s and 10 levels of the 4f12 ground configuration. A parametric interpretation of the levels has been carried out using the Cowan codes. Configuration interaction effects are discussed, in particular with the core-excited configurations 5p54f13 and 5p54f125d. Radial Slater parameters derived from 4f12 levels are larger than those pertaining to trivalent Tm ions in compounds. A selection of 105 prominent lines is given

Ab Initio Investigation of the Abstraction Reactions by H and D from Tetramethylsilane and Its Deuterated Substitutions

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Extended analysis of the Eu III spectrum

Aims. We create an Eu ii