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High-resolution far-ultraviolet broadband Fourier-transform photoabsorption spectra of ${}^{32}{\rm S}^{16}{\rm O}$, ${}^{33}{\rm S}^{16}{\rm O}$, ${}^{34}{\rm S}^{16}{\rm O}$, and ${}^{36}{\rm S}^{16}{\rm O}$ are recorded in a microwave discharge seeded with SO$_2$ . The $B{}^3{\Sigma}^-(v=4-30) \leftarrow X{}^3{\Sigma}^-(v=0)$ and $C{}^3{\Pi}(v=0-7) \leftarrow X{}^3{\Sigma}^-(v=0)$ bands are observed or inferred in the 43000 to 51000 cm$^{-1}$ (196 to 233 nm) spectral range. This is the first experimental detection of a $C{}^3{\Pi}(v>2)$ level and of any of these observed bands in an S-substituted isotopologue. Additional measurements of $A{}^3{\Pi}(v=1-3) \leftarrow X{}^3{\Sigma}^-(v=0)$ provide a calibration of the SO column density. Measured band profiles are fitted to an effective-Hamiltonian model of coupled excited $B{}^3{\Sigma}^-$ and $C{}^3{\Pi}$ states along with their predissociation linewidths and absorption band strengths. Electronic-state potential-energy curves and transition moments are deduced. The end result is a list of line frequencies, $f$-values, and dissociation widths describing the far-ultraviolet photodissociation spectrum of SO that is accurate enough for computing atmospheric photolytic isotope-fractionation.

The high-resolution B$^1\Sigma^+$ - A$^1\Pi$ (0, 0) and (0, 3) emission bands of the less-abundant $^{13}$C$^{17}$O isotopologue have been investigated by Fourier-transform spectroscopy in the visible region using a Bruker IFS 125HR spectrometer at an accuracy 0.003 cm$^{-1}$. These spectra are combined with high-resolution photoabsorption measurements of the $^{13}$C$^{17}$O B$^1\Sigma^+$ $\leftarrow$ X$^1\Sigma^+$ (0, 0), B$^1\Sigma^+$ $\leftarrow$ X$^1\Sigma^+$ (1, 0) and C$^1\Sigma^+$ $\leftarrow$ X$^1\Sigma^+$ (0, 0) bands recorded with an accuracy of 0.01 cm$^{-1}$ using the vacuum ultraviolet Fourier-transform spectrometer, installed on the DESIRS beamline at the SOLEIL synchrotron. In the studied 17,950 - 22,500 cm$^{-1}$ and 86,800 - 92,100 cm$^{-1}$ regions, 480 transitions have been measured. These new experimental data were combined with data from the C $\to$ A and B $\to$ A systems, previously analyzed in 13C17O. The frequencies of 1003 transitions derived from 12 bands were used to analyze the perturbations between the A$^1\Pi$ ($\nu$ = 0 - 3) levels and rovibrational levels of the d$^3\Delta_i$, e$^3\Sigma^-$, a$'{}^3\Sigma^+$, I$^1\Sigma^-$ and D$^1\Delta$ states as well as to a preliminary investigation of weak irregularities that appear in the B$^1\Sigma^+$ ($\nu$ = 0) level. Deperturbed molecular constants and term values of the A$^1\Pi$ state were obtained. The spin-orbit and L-uncoupling interaction parameters as well as isotopologue-independent spin-orbit and rotation-electronic perturbation parameters were derived., Comment: 37 pages, 8 tables, 7 figures, 91 references

Accurate Fourier-transform spectroscopic absorption measurements of vacuum ultraviolet transitions in atomic nitrogen and carbon were performed at the Soleil synchrotron. For $^{14}$N transitions from the $2s^22p^3\,^4$S$_{3/2}$ ground state and from the $2s^22p^3\,^2$P and $^2$D metastable states were determined in the $95 - 124$ nm range at an accuracy of $0.025\,\mathrm{cm}^{-1}$. Combination of these results with data from previous precision laser experiments in the vacuum ultraviolet range reveal an overall and consistent offset of -0.04 \wn\ from values reported in the NIST database. %The splitting of the $2s^22p^3\,^4$S$_{3/2}$ -- %$2s2p^4\,^4$P$_{5/2,3/2,1/2}$ The splittings of the $2s^22p^3\,^4$S$_{3/2}$ -- $2s2p^4\,^4$P$_{J}$ transitions are well-resolved for $^{14}$N and $^{15}$N and isotope shifts determined. While excitation of a $2p$ valence electron yields very small isotope shifts, excitation of a $2s$ core electron results in large isotope shifts, in agreement with theoretical predictions. For carbon six transitions from the ground $2s^22p^2\,^3$P$_{J}$ and $2s^22p3s\, ^3$P$_{J}$ excited states at $165$ nm are measured for both $^{12}$C and $^{13}$C isotopes.

Photoabsorption spectra of ${}^{14}{\rm N}{}^{15}{\rm N}$ were recorded at high resolution with a vacuum-ultraviolet Fourier-Transform spectrometer fed by synchrotron radiation in the range 81 to 100 nm. The combination of high column density ($3\times 10^{17}$ cm$^{-2}$) and low temperature (98 K) allowed for the recording of weak spin-forbidden absorption bands exciting levels of triplet character. The triplet states borrow intensity from ${}^1\Pi_u$ states of Rydberg and valence character while causing their predissociation. New predissociation linewidths and molecular constants are obtained for the states $C\,{}^3\Pi_u(v=7,8,14,15,16,21)$, $G\,{}^3\Pi_u(v=0,1,4)$, and $F\,{}^3\Pi_u(v=0)$. The positions and widths of these levels are shown to be well-predicted by a coupled-Schroedinger equation model with empirical parameters based on experimental data on ${}^{14}{\rm N}_2$ and ${}^{15}{\rm N}_2$ triplet levels., Comment: 16 pages, 16 figures

We have reinvestigated the A$^1\Pi$$(v=0)$ level of $^{13}$C$^{18}$O\ using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A$^1\Pi -\textrm{X}^1\Sigma^+$$(0, 0)$, e$^3\Sigma^--\textrm{X}^1\Sigma^+$$(1, 0)$, d$^3\Delta-\textrm{X}^1\Sigma^+$$(4, 0)$, a$'^3\Sigma^+-\textrm{X}^1\Sigma^+$$(9, 0)$, and \atX$(11, 0)$ bands. In addition, Fourier-transform emission spectroscopy in the visible range is performed on the ${\rm B}^1\Sigma^+-{\rm A}^1\Pi$$(0, 0)$ band. Spectra of the \BX$(0, 0)$ band are measured in order to tie information from the latter emission data to the level structure of A$^1\Pi$$(v=0)$. The high pressures in the absorption cell at the synchrotron and the high temperatures in the emission discharge permitted monitoring of high rotational quantum levels in A$^1\Pi$$(v=0)$ up to $J=43$. All information, in total over 900 spectral lines, was included in an effective-Hamiltonian analysis of the A$^1\Pi(v=0, J)$ levels that are directly perturbed by the e$\,^3\Sigma^-$$(v=1)$, d$^3\!\Delta$$(v=4)$, a$'^3\Sigma^+$$(v=9)$, d$^3\!\Delta$$(v=0)$, I$\,^1\Sigma^-$$(v=0, 1)$ close-lying levels and the e$\,^3\Sigma^-$$(v=0,2)$, d$^3\!\Delta$$(v=3,5)$, a$'^3\Sigma^+$$(v=8,10)$ remote levels, as well being indirectly influenced by the a$^3\Pi$$(v=10, 11)$ state. The influence of nine further perturber levels and their interactions was investigated and are not significant for reproducing the present experimental data. This analysis leads to a much improved description in terms of molecular constants and interaction parameters, compared to previous studies of the same energy region for other CO isotopologues., Comment: accepted Molecular Physics

Vacuum-ultraviolet (VUV) photoabsorption spectra were recorded of the $A\,{}^2\Sigma^+(v'=0)\leftarrow{}X\,{}^2\Pi(v''=0)$, $D\,{}^2\Sigma^-(v'=0)\leftarrow{}X\,{}^2\Pi(v''=0)$ and $D\,{}^2\Sigma^-(v'=1)\leftarrow{}X\,{}^2\Pi(v''=0)$ bands of the OH and OD radicals generated in a plasma-discharge source using synchrotron radiation as a background continuum coupled with the VUV Fourier-transform spectrometer on the DESIRS beamline of synchrotron SOLEIL. High-resolution spectra permitted the quantification of transition frequencies, relative $f$-values, and natural line broadening. The $f$-values were absolutely calibrated with respect to a previous measurement of $A\,{}^2\Sigma^+(v'=0)\leftarrow{}X\,{}^2\Pi(v''=0)$ ([wang1979]). Lifetime broadening of the excited $D\,{}^2\Sigma^-(v=0)$ and $D\,{}^2\Sigma^-(v=1)$ levels is measured for the first time and compared with previous experimental limits, and implies a lifetime 5 times shorter than a theoretical prediction ([van_der_loo2005]). A local perturbation of the $D\,{}^2\Sigma^-(v=0)$ level in OH was found.

The lowest $v=0$ level of the A$^1\Pi$, state of the $^{13}$C$^{16}$O isotopologue of carbon monoxide has been reinvestigated with a variety of high resolution spectroscopic techniques. The A$^1\Pi-$X$^1\Sigma^+(0,0)$ band has been studied by vacuum-ultraviolet Fourier-transform absorption spectroscopy, using the SOLEIL synchrotron as a radiation source. Spectra were obtained under quasi-static gas conditions at liquid-nitrogen temperature, room temperature and at an elevated temperature of 900 K, with absolute accuracies of 0.01$-$0.03 cm$^{-1}$. Two-photon Doppler-free laser spectroscopy has been applied to a limited number of transitions in the A$^1\Pi-$X$^1\Sigma^+(0,0)$ band, under collision-free circumstances of a molecular beam, yielding an absolute accuracy of 0.002 cm$^{-1}$. The third technique is high-resolution Fourier-transform emission spectroscopy in the visible region applied to the B$^1\Sigma^+-$A$^1\Pi(0,0)$ band in a gas discharge, at an absolute accuracy of up to 0.003 cm$^{-1}$. With these methods rotational levels of A$^1\Pi(0)$ could be studied in both parity components up to a rotational quantum number of $J=46$. The frequencies of 397 transitions were used to analyse the perturbations between the A$^1\Pi(0)$ level by vibrational levels of the D$^1\!\Delta$, e$^3\Sigma^-$, d$^3\!\Delta$, and a$'^3\Sigma^+$ states., Comment: 16 pages, 6 figures, 5 tables

The (2,0) (3,0) and (4,0) bands of the A$^1\Pi-$X$^1\Sigma^+$ system of $^{12}$C$^{16}$O have been re-investigated by high-resolution vacuum ultraviolet absorption spectroscopy. A VUV Fourier-transform spectrometer, illuminated by synchrotron radiation, was applied to record a jet-cooled spectrum, a room temperature static gas spectrum and a high temperature (900 K) quasi-static gas spectrum, resulting in absolute accuracies of 0.01$-$0.02 cm$^{-1}$ for the rotational line frequencies. Precise laser-based data were included in the analysis allowing for a highly accurate determination of band origins. Rotational levels up to $J=52$ were observed. The data were used to perform an improved analysis of the perturbations in the A$^1\Pi$, $v=2$, $v=3$, and $v=4$ levels by vibrational levels of the D$^1\Delta$, I$^1\Sigma^-$, e$^3\Sigma^-$, d$^3\Delta$, and a$'^3\Sigma^+$ states., Comment: 12 pages, 4 figures, 5 tables, Molecular Physics (2015) accepted

We study the formation of local magnetic moments and magnetic hyperfine fields at an \textit{s-p} impurity diluted in intermetallic Laves phases compounds $R$Ni$_{2}$ ($R$ = Nd, Sm, Gd, Tb, Dy) at finite temperatures. We start with a clean host and later the impurity is introduced. The host has two-coupled ($R$ and Ni) sublattice Hubbard Hamiltonians but the Ni sublattice can be disregarded because its $\textit{d}$ band, being full, is magnetically ineffective. Also, the effect of the $\textit{4f}$ electrons of $R$ is represented by a polarization of the \textit{d} band that would be produced by the $\textit{4f}$ magnetic field.This leaves us with a lattice of \textit{effective} rare earth \textit{R}-ions with only \textit{d} electrons. For the \textit{dd} electronic interaction we use the Hubbard-Stratonovich identity in a functional integral approach in the static saddle point approximation., Comment: 4 pages , 3 figures

Photoabsorption spectra of N$_2$ and CO were recorded at 900K, using the vacuum-ultraviolet Fourier-transform spectrometer at the DESIRS beamline of synchrotron SOLEIL. These high-temperature and high-resolution measurements allow for precise determination of line wavelengths, oscillator strengths, and predissociative line broadening of highly-excited rotational states with $J$ up to about 50, and also vibrational hot bands. In CO, the perturbation of $A\,{}^1\Pi-X\,{}^1\Sigma^+$ vibrational bands $(0,0)$ and $(1,0)$ were studied, as well as the transitions to perturbing optically-forbidden states $e\,{}^3\Sigma^-$, $d\,{}^3\Delta$, $D\,{}^1\Delta$ and $a'\,{}^3\Sigma^+$. In N$_2$, we observed line shifts and broadening in several $b\,{}^1\Pi_u-X\,{}^1\Sigma^+_g$ bands due to unobserved forbidden states of ${}^3\Pi_u$ symmetry. The observed state interactions are deperturbed and, for N$_2$, used to validate a coupled-channels model of the interacting electronic states. This data is appropriate for use in astrophysical or (exo-)planetary atmospheric applications where high temperatures are important and in future spectroscopic models of these molecules., Comment: 17 pages, 8 figures, 7 tables

Novel VUV sources and techniques for VUV spectroscopy are reviewed. Laser-based VUV sources have been developed via non-linear upconversion of laser pulses in the nanosecond (ns), the picosecond (ps), and femtosecond (fs) domain, and are applied in high-resolution gas phase spectroscopic studies. While the ns and ps pulsed laser sources, at Fourier-transform limited bandwidths, are used in wavelength scanning spectroscopy, the fs laser source is used in a two-pulse time delayed mode. In addition a Fourier-transform spectrometer for high resolution gas-phase spectroscopic studies in the VUV is described, exhibiting the multiplex advantage to measure many resonances simultaneously., Comment: 17 Pages, 8 figures, Conference proceedings of the VUV/X-ray 2013 at Hefei, China

The 3p\pi D^1\Pi_u state of the H_2 molecule was reinvestigated with different techniques at two synchrotron installations. The Fourier-Transform spectrometer in the vacuum ultraviolet wavelength range of the DESIRS beamline at the SOLEIL synchrotron was used for recording absorption spectra of the D^1\Pi_u state at high resolution and high absolute accuracy, limited only by the Doppler contribution at 100 K. From these measurements line positions were extracted, in particular for the narrow resonances involving ^1\Pi_u^- states, with an accuracy estimated at 0.06 cm^{-1} . The new data also closely match MQDT-calculations performed for the \Pi^- components observed via the narrow Q-lines. The \Lambda-doubling in the D^1\Pi_u state was determined up to v=17. The 10 m normal incidence scanning monochromator at the beamline U125/2 of the BESSY II synchrotron, combined with a home built target chamber and equipped with a variety of detectors was used to unravel information on ionization, dissociation and intramolecular fluorescence decay for the D^1\Pi_u vibrational series. The combined results yield accurate information of the characteristic Beutler-Fano profiles associated with the strongly predissociated \Pi_u^+ parity components of the D^1\Pi_u-levels. Values for the parameters describing the predissociation width as well as the Fano-q line shape parameters for the J=1 and J=2 rotational states were determined for the sequence of vibrational quantum numbers up to v=17., Comment: 11 pages, 9 figures, 1 table

The D^1\Pi_u - X^1\Sigma_g^+ absorption system of molecular deuterium has been re-investigated using the VUV Fourier -Transform (FT) spectrometer at the DESIRS beamline of the synchrotron SOLEIL and photon-induced fluorescence spectrometry (PIFS) using the 10 m normal incidence monochromator at the synchrotron BESSY II. Using the FT spectrometer absorption spectra in the range 72 - 82 nm were recorded in quasi static gas at 100 K and in a free flowing jet at a spectroscopic resolution of 0.50 and 0.20 cm^{-1} respectively . The narrow Q-branch transitions, probing states of \Pi^- symmetry, were observed up to vibrational level v = 22. The states of \Pi^+ symmetry, known to be broadened due to predissociation and giving rise to asymmetric Beutler-Fano resonances, were studied up to v = 18. The 10 m normal incidence beamline setup at BESSY II was used to simultaneously record absorption, dissociation, ionization and fluorescence decay channels from which information on the line intensities, predissociated widths, and Fano q-parameters were extracted. R-branch transitions were observed up to v = 23 for J = 1-3 as well as several transitions for J = 4 and 5 up to v = 22 and 18 respectively. The Q-branch transitions are found to weakly predissociate and were observed from v = 8 to the final vibrational level of the state v = 23. The spectroscopic study is supported by two theoretical frameworks. Results on the \Pi^- symmetry states are compared to ab initio multi-channel-quantum defect theory (MQDT) calculations, demonstrating that these calculations are accurate to within 0.5 cm^-1., Comment: 16 pages, 10 figures, 2 tables, supplemental material with an additional table

The $\textrm{A}^1\Pi-\textrm{X}^1\Sigma^+$ band system of carbon monoxide, which has been detected in six highly redshifted galaxies ($z=1.6-2.7$), is identified as a novel probe method to search for possible variations of the proton-electron mass ratio ($\mu$) on cosmological time scales. Laboratory wavelengths of the spectral lines of the A-X ($v$,0) bands for $v=0-9$ have been determined at an accuracy of $\Delta\lambda/\lambda=1.5 \times 10^{-7}$ through VUV Fourier-transform absorption spectroscopy, providing a comprehensive and accurate zero-redshift data set. For the (0,0) and (1,0) bands, two-photon Doppler-free laser spectroscopy has been applied at the $3 \times 10^{-8}$ accuracy level, verifying the absorption data. Sensitivity coefficients $K_{\mu}$ for a varying $\mu$ have been calculated for the CO A-X bands, so that an operational method results to search for $\mu$-variation., Comment: 7 pages (main article), 3 figures, includes supplementary material

Magnetic hyperfine field at Cu isotopes as impurities in Fe were recently measured at low temperature. A model to explain these experimental results is proposed. The diluted Cu impurities in the ferromagnetic Fe host are described by an extension of the Daniel-Friedel model, including the next neighbor perturbation. In order to account for the available experimental data in Cu isotopes with atomic masses $A$ = 59, 67, 69 and 71 as impurity, we needed to incorporate the Cu anomaly volume in the effective charge to be screened and in the self-consistent procedures.

The first comprehensive high-resolution photoabsorption spectrum of 14N15N has been recorded using the Fourier-transform spectrometer attached to the Desirs beamline at the Soleil synchrotron. Observations are made in the extreme ultraviolet (XUV) and span 100,000-109,000 cm-1 (100-91.7 nm). The observed absorption lines have been assigned to 25 bands and reduced to a set of transition energies, f values, and linewidths. This analysis has verified the predictions of a theoretical model of N2 that simulates its photoabsorption and photodissociation cross section by solution of an isotopomer independent formulation of the coupled-channel Schroedinger equation. The mass dependence of predissociation linewidths and oscillator strengths is clearly evident and many local perturbations of transition energies, strengths, and widths within individual rotational series have been observed., Comment: 14 pages, 8 figures, one data archive

A great deal of experimental work using perturbed angular correlation (PAC) has succeed in measuring hyperfine fields in Ce diluted in metallic systems, thus allowing the determination of the local impurity moment at low temperatures. Motivated by such experimental work on Ce(140) placed on a R site of the rare earth (R = Gd, Tb, Dy, Ho, Er) in RCo_2, we theoretically discuss, within a simple model, the local magnetic moments and thereby calculate the magnetic hyperfine fields. The results are in good agreement with the experimental data. For the sake of comparison we recall our previous results on Ta d-impurity embedded in the same hosts., Comment: Presented in 11th Joint MMM/Intermag Conference, Washington 2010

Recent experimental results for the magnetic hyperfine field B_{\rm hf} at the nuclei of \textit{s-p} impurities such as ${}^{119}$Sn in intermetallic Laves phases RM_2 (R = Gd, Tb, Dy, Ho, Er; M = Fe, Co) and ${}^{111}$Cd in RCo_{2}, the impurity occupying a $R$ site indicate that the ratio B_{\rm hf}/\mu_{3d} exhibits different behavior when one goes from RFe_2 to RCo_2. In this work, we calculate these local moments and the magnetic hyperfine fields. In our model, B_{\rm hf} has two contributions: one arising from the $R$ ions, and the other arising from magnetic 3d-elements; these separate contributions allow the identification of the origin of different behavior of the ratio mentioned above. For {}^{111}Cd in RCo_2 we present also the contributions for B_{\rm hf} in the light rare earth Pr, Nd, Pm, Sm compounds. For the sake of comparison we apply also the model to {}^{111}Cd diluted in RNi_2. Our self-consistent magnetic hyperfine field results are in good agreement with those recent experimental data., Comment: Presented in ICM2009 in Karlsruhe, Germany