Doublet Lines Research Articles

Shock Wave Driven by an Expanding System of Loops

We report on a Coronal Mass Ejection (CME) observed on June 27, 1999 by the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board the SOHO spacecraft. The CME was also observed by the Large Angle Spectroscopic Coronagraph (LASCO). Emission of hot material has been recorded by UVCS propagating in front of an opening system of loops generated by the CME. The evolution of the UVCS structure is highly correlated with the evolution of the open- ing loop. The data reveal excess broadening of the O  doublet lines and an enhancement in the intensity of the Si  λ520.66 and λ499.37 lines due to the motion of the expanding hot gas. The hot gas emission seems to be due to a shock wave propagating in front of a very fast gas bubble traveling along the opening loop system.

Shock wave driven by an expanding system of loops

We report on a Coronal Mass Ejection (CME) observed on June 27, 1999 by the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board the SOHO spacecraft. The CME was also observed by the Large Angle Spectroscopic Coronagraph (LASCO). Emission of hot material has been recorded by UVCS propagating in front of an opening system of loops generated by the CME. The evolution of the UVCS structure is highly correlated with the evolution of the open- ing loop. The data reveal excess broadening of the O  doublet lines and an enhancement in the intensity of the Si  λ520.66 and λ499.37 lines due to the motion of the expanding hot gas. The hot gas emission seems to be due to a shock wave propagating in front of a very fast gas bubble traveling along the opening loop system.

Experimental and Theoretical Evaluation of Density‐sensitive Nvi, Arxiv, and FexxiiLine Ratios

The line ratios of the 2p-3d transitions in the boron-like spectra Ar XIV and Fe XXII have been measured using the electron beam ion traps at Lawrence Livermore National Laboratory. Radiative-collisional model calculations show these line ratios to be sensitive to the electron density in the ranges ne = 1010-1012?cm-3 and ne = 1013-1015?cm-3, respectively. In our experiment, the electron beam density of about 1011?cm-3 was varied by about a factor of 5. Our data show a density effect for the line doublet in Ar XIV, and good agreement with theory is found. The relative intensity of the Fe XXII doublet shows good agreement with our predicted low-density limit. The N VI K-shell spectrum was used to infer the actual electron density in the overlap region of ion cloud and electron beam, and systematic measurements and calculations of this spectrum are presented as well. The Ar XIV and Fe XXII spectra promise to be reliable density diagnostics for stellar coronae, complementing the K-shell diagnostics of helium-like ions.

Positive and negative dispersion in an Er^3+-doped yttrium aluminum garnet crystal

We investigate a four-level system in the Er3+-doped yttrium aluminum garnet crystal that can produce an absorption or gain doublet in the probe absorption spectrum when driven by a coherent field and incoherent pumping. It is found that the transparent linear positive or negative dispersion can occur between the doublet lines. We show that the group index of a probe pulse can be manipulated when we control the incoherent pumping and the coherent field.

Study of mechanically alloyed nano Cu-Fe particles with a heterostructure

The magnetic alloys of Cu-Fe (Cu 50 Fe 50 , Cu 80 Fe 20 and Cu 90 Fe 10 ) were prepared by a mechanical alloying method and their structural and magnetic behaviors were examined by X-ray diffraction and Mossbauer spectra. The magnetization curves did not distinctly show the saturation at 70 kOe for the concentrated alloys of Cu 80 Fe 20 and Cu 90 Fe 10 . The Mossbauer spectrum of Cu 80 Fe 20 at room temperature shows one Lorentzian line of the paramagnetic phase, whereas the Mossbauer spectrum of Cu 90 Fe 10 consists of a sextet Lorentzian line at room temperature and a centered doublet line. The Mossbauer spectra of Cu 90 Fe 10 measured in the temperature ranges from 13 to 295 K, implies that Cu 90 Fe 10 consists of two magnetic phases. One superimposed sextet corresponds to the ferromagnetic iron in Cu matrix and the other one indicates the superparamagnetic iron rich phase.

Hyperfine structure in H$\mathsf{^{13}}$CO$\mathsf{^{+}}$ and $\mathsf{^{13}}$CO: Measurement, analysis, and consequences for the study of dark clouds

The magnetic moment of the 13 C nucleus is shown to provide a potentially useful tool for analysing quiescent cold molecular clouds. We report discovery of hyperfine structure in the lowest rotational transition of H 13 CO + . The doublet splitting in H 13 CO + , observed to be of width 38.5 ± 5.2 kHz or 0.133 km s −1 , is confirmed by quantum chemical calculations which give a separation of 39.8 kHz and line strength ratio 3:1 when H and 13 C nuclear spin-rotation and spin-spin coupling between both nuclei are taken into account. We improve the spectroscopic constants of H 13 CO + and determine the hitherto uncertain frequencies of its low-J spectrum to better precision by analysing the dark cloud L 1512. Attention is drawn to potentially high optical depths (3 to 5 in L 1512) in quiescent clouds, and examples are given for the need to consider the (1-0) line's doublet nature when comparing to other molecular species, redirecting or reversing conclusions arrived at previously by single- component interpretations. We further confirm the hyperfine splitting in the (1-0) rotational transition of 13 CO that had already been theoretically predicted, and measured in the laboratory, to be of width about 46 kHz or, again, 0.13 km s −1 . By applying hyperfine analysis to the extensive data set of the first IRAM key-project we show that 13 CO optical depths can as for H 13 CO + be estimated in narrow linewidth regions without recourse to other transitions nor to assumptions on beam filling factors, and linewidth and velocity determinations can be improved. Thus, for the core of L 1512 we find an inverse proportionality between linewidth and column density, resp. linewidth and square root of optical depth, and a systematic inside-out increase of excitation temperature and of the 13 CO:C 18 O abundance ratio. Overall motion toward the innermost region is suggested.

Time Resolved EPR of Excited Triplet C60 Aligned in Nematic Liquid Crystals

The photoexcited triplet states of fullerenes C60 and C70 dissolved in a nematic liquid-crystal solvent have been investigated using time-resolved EPR (TR-EPR) spectroscopy. Triplet spectra composed of two lines with opposite polarization (enhanced absorption and emission) and small line widths have been recorded for C60, but much broader lines are recorded for C70. The Jahn−Teller dynamic distortion of C60 is responsible for the motional narrowing of the triplet lines, and the partial orientation induced by the nematic solvent removes the degeneracy of the two triplet transitions giving rise to a doublet of lines. Broad features appearing at low temperatures in the nematic phase are attributed to the local disorder induced by the dissipation of excess energy in the photoexcitation process. The time decay of the TR-EPR signals is explained by a kinetic model for the spin-level populations including spin relaxation and selective decay of the spin sublevels.

VLT + UVES spectroscopy of the low-ionization intrinsic absorber in SDSS J001130.56+005550.7

We analyse high-resolution VLT+UVES spectra of the low-ionization intrinsic absorber observed in the BAL QSO SDSS J001130.56+005550.7. Two narrow absorption systems at velocities -600 km s-1 and -22 000 km s-1 are detected. The low-velocity system is part of the broad absorption line (BAL), while the high-velocity one is well detached. While most narrow absorption components are only detected in the high-ionization species, the lowest velocity component is detected in both high- and low-ionization species, including in the excited and lines. From the analysis of doublet lines, we find that the narrow absorption lines at the low-velocity end of the BAL trough are completely saturated but do not reach zero flux, their profiles being dominated by a velocity-dependent covering factor. The covering factor is significantly smaller for than for and , which demonstrates the intrinsic nature of absorber. From the analysis of the excited and lines in the lowest velocity component, we find an electron density 103 cm-3. Assuming photoionization equilibrium, we derive a distance 20 kpc between the low-ionization region and the quasar core. The correspondence in velocity of the high- and low-ionization features suggests that all these species must be closely associated, hence formed at the same distance of ~20 kpc, much higher than the distance usually assumed for BAL absorbers.

SOLEX: a tunable monochromatic X-ray source in the 1–20 keV energy range for metrology

A tunable monochromatic X-ray source covering the 1-20 keV energy range is described. The initial X-ray beam is obtained from a dedicated windowless X-ray tube. The energy selection is performed through a cylindrically bent crystal, used either in the reflection (Johann geometry) or in the transmission (Cauchois geometry) mode, by rotating the crystal holder by a 90° angle. Contrary to conventional geometries where the X-ray tube is fixed, here the direction of the exit beam impinging the X-ray detector is fixed. This setup is shown to be useful for various studies: high-resolution spectrometry, characterization of the response function and the efficiency of detectors and optical components, determination of transmission characteristics of different materials. Observations of the Lα line and Kα doublet from a copper anode are presented, that demonstrate the performance of this new setup.

Mössbauer spectra of single-domain particles with rotating magnetic moments

The influence of the rotation of a particle’s magnetic moment in the magneticanisotropy field on the shape of the Mössbauer spectra of hyperfine structure is analysedtheoretically. It is found that, due to rotation, a renormalization of the nuclearg-factorsoccurs, which results in a qualitative transformation of Mössbauerabsorption spectra. In particular, along with the magnetic sextet whichis well known in the Mössbauer spectroscopy of the 57Feisotope, partial spectra can be formed that consist of ‘magnetic’ quintuplet,quartet, triplet and even doublet lines. This peculiarity in forming the spectra ofmagnetic hyperfine structure should be taken into account in analysing theMössbauer spectra of materials with nano-sized magnetic particles.

New type of brightness variations of the colliding wind WO4 + O5((f)) binary WR 30a

We present new photometric observations in Johnson V and B of WR 30a, revealing relative dramatic changes in brightness of 0: m 2. These variations occur on a time scale of hours, and are only seen in V. We argue that they are not caused by dust extinction, but either by a dramatic change in the strength of the C iv 5801-12 A emission line doublet due to a de-excitation process, or by some unknown continuum eect.

Surprisingly Little OviEmission Arises in the Local Bubble

This paper reports the first study of the O VI resonance line emission (λλ1032, 1038) originating in the Local Bubble (or Local Hot Bubble) surrounding the solar neighborhood. In spite of the fact that O VI absorption within the Local Bubble has been observed, no resonance line emission was detected during our 230 ks Far Ultraviolet Spectroscopic Explorer observation of a "shadowing" filament in the southern Galactic hemisphere. As a result, tight 2 σ upper limits are set on the intensities in the 1032 and 1038 Å emission lines: 500 and 530 photons cm-2 s-1 sr-1, respectively. These values place strict constraints on models and simulations. They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside in distinct regions of the Local Bubble and are not mixed in a single plasma, whether in equilibrium with T ~ 106 K or highly overionized with T ~ 4 to 6 × 106 K. If the line of sight intersects multiple cool clouds within the Local Bubble, then the results also suggest that hot/cool transition zones differ from those in current simulations. With these intensity upper limits, we establish limits on the electron density, thermal pressure, path length, and cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore, the intensity of O VI resonance line doublet photons originating in the Galactic thick disk and halo is determined (3500-4300 photons cm-2 s-1 sr-1), and the electron density, thermal pressure, path length, and cooling timescale of its O VI-bearing plasma are calculated. The pressure in the Galactic halo's O VI-bearing plasma (3100-3800 K cm-3) agrees with model predictions for the total pressure in the thick disk/lower halo. We also report the results of searches for the emission signatures of interstellar C I, C II, C III, N I, N II, N III, Mg II, Si II, S II, S III, S IV, S VI, Fe II, and Fe III.

The Nascent Solar Wind: Origin and Acceleration

High-speed solar wind is known to originate in polar coronal holes, which, however, are made up of two components: bright, high-density regions known as and dark, weakly emitting low-density regions known as interplumes. Recent space observations have shown that the width of UV lines is larger in interplume regions, while observations of the ratio of the O VI doublet lines at 1032 and 1037 A, at 1.7 solar radii, suggest higher outflows in interplume regions than in plumes at that altitude. These results favor interplume regions as sources of the fast solar wind. The present work aims at investigating the outflow speed versus altitude properties of the O VI and H I ions, at heights below 2 solar radii, in both plumes and interplume regions. To this end, we examined Solar Ultraviolet Measurement of Emitted Radiation (SUMER) and Ultraviolet Coronagraph Spectrometer (UVCS) observations of a north polar coronal hole taken on 1996 June 3, over the altitude range between 1 and 2 solar radii, and through a Doppler dimming analysis of our data, we show that interplume areas may be really identified as sources of fast wind streams. The behavior of plumes, on the contrary, can be interpreted in terms of static structures embedded in the interplume ambient. We conclude by comparing our results with the predictions of theoretical models of the solar wind and giving an empirical estimate of the heating rate, per particle, for H I and O VI ions in interplume regions at 1.75 and 2.0 solar radii.

Plasma properties above coronal active regions inferred from SOHO/UVCS and radio spectrograph observations

Information on coronal plasma was inferred from the joint analysis of type  radio bursts and SOHO UltraViolet Coronagraph Spectrometer (UVCS) observations. The data sample comprises 37 metric type  radio bursts observed by ground- based radio spectrographs in 1999, during the rising phase of the solar cycle. The coronal electron densities ne were estimated with the diagnostic provided by UVCS observations of the O  doublet line intensities. Upper limits to the coronal Alfven speed above active regions were inferred from the derived shock speeds by requiring that the disturbances propagate at least faster than the local characteristic speed. Information on the magnetic field strength B and plasma β in the middle corona were finally extracted from the coronal Alfven speed upper limits. A major improvement with respect to previous studies that used type  radio bursts to derive plasma properties, is that density profiles of the pre-shock plasma obtained a few hours before the passage of the shock were used instead of general electron density models taken from literature. Our main result is expressed by the inequality B(r) ≤ (0.6 ± 0.3)(r − 1) −1.2 G, that is valid in the range 1.5 ≤ r ≤ 2.3 solar radii, and is consistent with previous estimates of the magnetic field above coronal active regions.

The Esr Study of Complexation and Nanoclusters Growth in Silver-Liquid Crystal System

The ESR spectrum of Ag-5CB (C 5 H 11 -C 6 H 4 -C 6 H 4 -CN) and Ag-5Py (C 5 H 11 -C 5 H 3 N-C 6 H 4 -CN) co-condensate film at 90 K showed two doublet lines due to silver atoms included in ~ -complexes with cyanobiphenyls and wide anisotropic singlet line with g-factor equal to 2.0030, that could be referred to small silver clusters. It was found the integral intensity of doublet lines decreased during the annealing of samples in temperature range 80-200 K due to thermal decomposition of Ag-5CB complex followed by the aggregation of silver atoms.

The Effects of Inhomogeneous Absorbers on the Formation of Intrinsic Quasar Absorption Lines

We investigate the formation of absorption lines in an inhomogeneous medium covering an extended source, in the context of intrinsic quasar (QSO) absorption lines. We first describe a simple formalism to model the effect of having a range of column densities in front of the source. It is shown that if the probability distribution of column densities is a power law with index p, the remaining flux in a line in which the medium is very optically thick scales as τ-(p+1), where τ is the maximum optical depth in front of the source. This power-law behavior appears to give a better description of the observed relation between optical depth and flux near the bottom of strong intrinsic QSO absorption lines than the standard exponential behavior. The formalism provides an alternative to the model that assumes partial homogeneous covering, which is the current standard in the interpretation of intrinsic QSO absorption lines that do not show exponential behavior, and in some respects provides a better fit to the observed line strengths. We show that inhomogeneous covering can lead to an apparent velocity-dependent covering factor if the partial homogeneous covering model is applied to doublet lines. The covering factor derived from a partial homogeneous covering analysis does, however, yield information on the characteristics of the column density distribution, such as the sharpness of the edges and peaks. We apply the inhomogeneous covering formalism to two observed QSO absorption-line systems to demonstrate these effects.

Directional behavior of nuclear quadrupole resonance in YBa2Cu3O6

Abstract Powder samples of YBa 2 Cu 3 O 6 were magnetically aligned and the anisotropies in the systems were studied by means of Cu(1) nuclear quadrupole resonance (NQR) in the absence of external magnetic fields. Our room temperature measurements of the NQR lineshapes and the spin–lattice and spin–spin relaxation times as a function of the aligning magnetic field indicate that full microscopic alignment can be achieved by using a magnetic field of about 4.7 T, for which doublet line patterns arising from a hyperfine splitting were observed.

Echelle observations of chromospheric activity in post-common-envelope binaries

We present high-resolution echelle spectroscopy that confirms, via the identification of numerous chromospheric emission lines, the extremely high levels of chromospheric activity displayed by the secondary stars in post-common-envelope binaries (PCEBs). Furthermore, the EG UMa data set includes the first ever high-resolution spectroscopic observations of flare activity in a PCEB system. The nature of the EG UMa spectra is investigated and a two-flare model that explains all of the observed emission-line features is identified. V-band photometry of EG UMa includes a further flare event, but contains no evidence of pulsations from the white dwarf primary star in this system. The extensive spectral-line emission observed in EG UMa is also observed in HZ 9. The criteria used to identify flare events in the EG UMa data is employed to classify the HZ 9 spectrum as an observation of extremely high level, quiescent, chromospheric activity, and not arising from a flare event. PG 1026+002 and RE J1629+780 both display H Balmer and He i D3 line emission. The observed activity of the secondary star in PG 1026+002 appears, however, to be at a lower level than that exhibited by the secondary stars in EG UMa, HZ 9 and RE J1629+780. It is not clear why PG 1026+002 should be exhibiting a lower level of activity, nor is it possible to deduce whether this is a transient phenomenon. The only spectral features attributable to the secondary star in GD 123 are weak Hα line emission and Na i doublet line absorption at 8183, 8195 A. The He i D3 line is a magnetic activity indicator and its presence in all of the PCEB spectra, with exception of GD 123, is direct evidence for the maintenance of magnetic fields in all of these late-type, fully convective, dwarf secondary stars.

Profiles of the resonance doublets formed in bipolar winds in symbiotic stars

We compute the profiles of resonance doublet lines (S1/2‐P1/2,3/2) formed in bipolar winds with velocity greater than the doublet separation in symbiotic stars. Particular attention has been paid to the doublet line ratio, where an essential role is played by the conversion of the short-wavelength component arising from the S1/2‐P3/2 transition into the long-wavelength component for the transition S1/2‐P1/2. We adopted a Monte Carlo technique and the Sobolev approximation. Our bipolar winds take the form of a cone and are characterized by the terminal wind velocity, the mass-loss rate and the opening angle of the cone. When an observer is in the polar direction and the Sobolev optical depth τSob � 1, we mainly obtain profiles with inverted flux line ratios, where the short-wavelength component is weaker than the long-wavelength component. When an observer is in the equatorial direction, we find that the profiles are characterized by two broad components, where the long-wavelength component is the broader and stronger of the two. We conclude that the profiles obtained in our model provide a qualitative understanding of the broad profiles and inverted intensity ratios of the doublets in symbiotic

Accurate Calculations of Interstellar Lines of Mg+Using the Coupled Cluster Approach

One of the most successful ab initio, highly correlated all-order many-body methods, the relativistic coupled cluster theory, is employed to calculate excitation energies of the doublet states of Mg+ and allowed transitions among them that are of interest in astrophysical problems. We have also calculated oscillator strength for the 3s-4p doublet transitions, which is improved over the existing results. These transition lines have been sought after in astronomical observations because they represent the best column density identifier in the interstellar medium. Our calculated oscillator strength (9.3 × 10-4) and branching ratio (1.80) of these doublet lines matches well with the recent empirical and semiempirical calculations.