Band Head Research Articles

Star formation and jet-induced coronal lines near the core of NGC 1068

Context. Active galactic nuclei (AGNs) are very luminous galaxies from the ultraviolet (UV) to the far infrared (FIR). To study regions near the core, which are dominated by dust, IR is the perfect spectral range because of the lower optical depth of the dust. However, these galaxies are usually distant, and the structures near the core are faint compared to the central source. High resolution and high contrast are mandatory to study the inner structures of AGNs and better understand the interaction between the central core and its surroundings.Aims. Our goal is to propose an explanation for the coronal lines in our spectra of NGC 1068 at a far distance (few tens of parsec) from the central source inside wave-like structures that we call nodules.Methods. NGC 1068 was observed with NaCo at ESO/VLT, using long-slit spectroscopy at 2.2 μ m and 3.5 μ m. Reduced spectra were compared to the output of Cloudy, using various ionizing continua: the continuum of the central source, young stars, and radiative shocks caused by the jet.Results. For the first time, thanks to the resolution provided by NaCo, near-IR coronal emission can be precisely associated to structures observable in the IR broad-band images. We found that coronal lines observed in the nodules cannot be caused by photoionization by the central source but are instead caused by a local jet-induced ionizing continuum. In addition, studying the Brackett-γ line (Brγ ) and CO 2-0 band head, we deduced a star density within the four nodules (~800 000 stars) compatible with super star cluster (hereafter SSC) models.

Chemical composition of evolved stars in the open cluster NGC 2506

In this study we present abundances of 12^C, 13^C, N, O and up to 26 other chemical elements in two first ascent giants and two core-helium-burning 'clump' stars of the open cluster NGC 2506. Abundances of carbon were derived using the C_2 Swan (0,1) band head at 5635.5 A. The wavelength interval 7940-8130 A, with strong CN features, was analysed in order to determine nitrogen abundances and carbon isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 A. NGC 2506 was found to have a mean [Fe/H]=-0.24 +- 0.05 (standard deviation). Compared with the Sun and other dwarf stars of the Galactic disc, mean abundances in the investigated clump stars suggest that carbon is depleted by about 0.2 dex, nitrogen is overabundant by about 0.3 dex and other chemical elements have abundance ratios close to solar. The C/N and 12^C/13^C ratios are lowered to 1.25 +- 0.27 and 11 +- 3, respectively.

Determination of the spectroscopic properties of indium bromide

To develop a more efficient plasma light source, molecules are considered as the prime source of radiation because they can potentially avoid the conversion losses of the low-pressure mercury lamp as well as the thermal losses of the high-pressure mercury lamps. A candidate to serve as the prime radiator in such a lamp could be indium bromide, but spectroscopic data to assess its aptitude are largely unavailable. To increase the knowledge of the spectroscopic properties of these molecules and InBr in particular, an experiment was designed to acquire this information. Laser-induced fluorescence was used to study the radiative properties of InBr for lighting purposes. Using an innovative method to interpret the measured data, detection--excitation (detex) plots, more information can be obtained from the spectra. Also the effect of a background gas and plasma was investigated for both a capacitive and an inductive plasma. Mainly the electronic A-state of InBr was investigated. Results include newly identified rotational transitions, vibrational constants, rotational constants for different vibrational levels, band head wave numbers and Franck–Condon factors for various vibrational transitions.

MICROSCOPIC STUDY OF NEGATIVE PARITY YRAST STATES IN NEUTRON-DEFICIENT 119–127Ba ISOTOPES

The negative parity yrast bands of neutron-deficient 119–127 Ba nuclei are studied by using the Projected Shell Model approach. Energy levels, transition energies and B(M1)/B(E2) ratios are calculated and compared with the available experimental data. The calculations reproduce the band head spins of negative parity yrast bands and indicate the multi-quasiparticle structure for these bands.

AMBER observations of the AGB star RS Capricorni: extended atmosphere and comparison with stellar models

We report on K-band VLTI/AMBER observations at medium spectral resolution ($\sim$1500) of RS Capricorni, an M6/M7III semi-regular AGB star. From the spectrally-dispersed visibilities, we measure the star diameter as a function of observing wavelength from 2.13 to 2.47 microns. We derive a Rosseland angular diameter of $7.95 \pm 0.07$ mas, which corresponds to an effective temperature of $3160 \pm 160$ K. We detect size variations of around 10% in the CO band heads, indicating strong opacity effects of CO in the stellar photosphere. We also detect a linear increase of the size as a function of wavelength, beginning at 2.29 microns. Models of the stellar atmosphere, based on the mass of the star as estimated from stellar-evolution models, predict CO-size effects about half of those observed, and cannot reproduce the linear size increase with wavelength, redward of 2.29 microns. We are able to model this linear size increase with the addition of an extended water-vapor envelope around the star. However, we are not able to fit the data in the CO bandheads. Either the mass of the star is overestimated by the stellar-evolution models and/or there is an additional extended CO envelope in the outer part of the atmosphere. In any case, neither the water-vapor envelope, nor the CO envelope, can be explained using the current models.

Chemical composition of evolved stars in the open cluster IC 4651★

We present an analysis of high-resolution spectra of three core-helium-burning "clump" stars and two first ascent giants in the open cluster IC 4651. Atmospheric parameters (T_eff, log_g, v_t, and [Fe/H]) were determined in our previous study by Carretta et al. (2004). In this study we present abundances of C, N, O and up to 24 other chemical elements. Abundances of carbon were derived using the C_2 Swan (0,1) band head at 5635.5 A. The wavelength interval 7980-8130 A, with strong CN features, was analysed in order to determine nitrogen abundances and 12^C/13^C isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 A. Compared with the Sun and other dwarf stars of the Galactic disk, mean abundances in the investigated clump stars suggest that carbon is depleted by about 0.3 dex, nitrogen is overabundant by about 0.2 dex and oxygen is close to solar. This has the effect of lowering the mean C/N ratio to 1.36 +- 0.11. The mean 12^C/13^C ratios are lowered to 16 +- 2. Other investigated chemical elements have abundance ratios close to the solar ones.

Surface symmetry energy of nuclear energy density functionals

We study the bulk deformation properties of the Skyrme nuclear energy density functionals (EDFs). Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band heads in Hg and Pb isotopes and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear EDFs. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.

Optical and near-infrared velocity dispersions of early-type galaxies★

We have carried out a systematic, homogeneous comparison of optical and near-infrared dispersions. Our magnitude-limited sample of early-type galaxies in the Fornax cluster comprises 11 elliptical and 11 lenticular galaxies more luminous than MB = -17. We were able to determine the central dispersions based on the near-infrared CO absorption band head for 19 of those galaxies. The velocity dispersions range from less than 70 km/s to over 400 km/s. We compare our near-infrared velocity dispersions to the optical dispersions measured by Kuntschner (2000). Contrary to previous studies, we find a one-to-one correspondence with a median fractional difference of 6.4%. We examine the correlation between the relative dust mass and the fractional difference of the velocity dispersions, but find no significant trend. Our results suggest that early-type galaxies are largely optically thin, which is consistent with recent Herschel observations.

Spin, quadrupole moment, and deformation of the magnetic-rotational band head inPb193

The spectroscopic quadrupole moment of the ${T}_{1/2}=9.4(5)$ ns isomer in $^{193}\mathrm{Pb}$ at an excitation energy ${E}_{\mathrm{ex}}=(2585+x)$ keV is measured by the time-differential perturbed angular distribution method as $|{Q}_{s}|=2.6(3)$ $e$ b. Spin and parity ${I}^{\ensuremath{\pi}}=27/{2}^{\ensuremath{-}}$ are assigned to it based on angular distribution measurements. This state is the band head of a magnetic-rotational band, described by the $1{i}_{13/2}$ subshell with the $(3{s}_{1/2}^{\ensuremath{-}2}1{h}_{9/2}1{i}_{13/2}){}_{{11}^{\ensuremath{-}}}$ proton excitation. The pairing-plus-quadrupole tilted-axis cranking calculations reproduce the measured quadrupole moment with a moderate oblate deformation ${\ensuremath{\epsilon}}_{2}=\ensuremath{-}0.11$, similar to that of the ${11}^{\ensuremath{-}}$proton intruder states, which nuclei in the region. This is the first direct measurement of a quadrupole moment and thus of the deformation of a magnetic-rotational band head.

ClO Radical Yields in the Reaction of O(1D) with Cl2, HCl, Chloromethanes, and Chlorofluoromethanes

Absolute ClO radical product yields in the gas-phase reactions of O((1)D) with Cl(2), HCl, CCl(4), CHCl(3), CH(2)Cl(2), CH(3)Cl, CFCl(3), CF(2)Cl(2), CF(3)Cl, CHFCl(2), and CHF(2)Cl are reported. Product yields were measured using pulsed-laser photolysis of O(3) to produce O((1)D) in the presence of excess reactant combined with dual wavelength differential cavity ring-down spectroscopic detection of the ClO radical. ClO radical absorption cross sections for the A(2)Π(v = 10) ← X(2)Π(v = 0) transition band head near 280 nm were determined between 200 and 296 K as part of this work. The ClO product yields obtained at room temperature were Cl(2) (0.77 ± 0.10), HCl (0.20 ± 0.04), CCl(4) (0.79 ± 0.04), CHCl(3) (0.77 ± 0.04), CH(2)Cl(2) (0.73 ± 0.04), CH(3)Cl (0.46 ± 0.06), CFCl(3) (0.79 ± 0.04), CF(2)Cl(2) (0.76 ± 0.06), CF(3)Cl (0.82 ± 0.06), CHFCl(2) (0.73 ± 0.05), and CHF(2)Cl (0.56 ± 0.03), where the quoted error limits are 2σ of the measurement precision. ClO product yields in the O((1)D) + Cl(2) and CFCl(3) reactions were found to be independent of temperature between 200 and 296 K, within the precision of the measurements. The absolute ClO yields obtained in this study are compared with previously reported values determined using relative and indirect methods.

Spectral interferences from formaldehyde in CH PLIF flame front imaging with broadband B-X excitation

In this letter we show that the use of slightly broadband laser sources like multimode alexandrite lasers for CH PLIF bears the danger of interferences from formaldehyde. Such interferences occur when the laser frequency is not carefully tuned to the B-X (0,0) R-branch band head at around 387.2 nm and manifest either in the appearance of an additional layer in the PLIF image or in a slight broadening of the actual CH layer. With careful frequency selection the formaldehyde signals were not observed. Suppression of the interferences is feasible by employing appropriate spectral filters.

Radiative transition parameters of the [formula omitted] band system

The relative band strengths of several absorption bands of the Ag 2 C 1 Π u – X 1 Σ g + system are measured for the first time. Ratios of observed strengths for bands with common lower vibronic levels are compared with theoretically predicted absorption band oscillator strengths, which we computed by numerically solving the radial Schrödinger equation for the vibrational wave functions, ψ υ ′ and ψ υ ″ of the Ag 2 107 , 109 C 1 Π u – X 1 Σ g + band system, using Rydberg–Klein–Rees potential energy curves and a suitable choice for the electronic transition moment function. This resulted in a useful set of radiative transition parameters for a large matrix of Ag 2 C– X bands. The functional form of the electronic transition moment required by the observed band strength ratios forces good agreement between the observations and diatomic molecular theory. Since the function is highly nonlinear, the commonly applied r-centroid approximation is invalid, and numerical integration of ∫ ψ υ ′ * R e ( r ) ψ υ ″ dr had to be performed instead. As a final check on the reliability of our results, we find good agreement between the experimentally measured displacements of band heads for the Ag 2 107 , 107 and Ag 2 109 , 109 isotopologues and the corresponding isotopic shifts of our calculated band origins.

C, N and O abundances in red clump stars of the Milky Way

The Hipparcos orbiting observatory has revealed a large number of helium-core-burning "clump" stars in the Galactic field. These low-mass stars exhibit signatures of extra-mixing processes that require modeling beyond the first dredge-up of standard models. The 12C/13C ratio is the most robust diagnostic of deep mixing, because it is insensitive to the adopted stellar parameters. In this work we present 12C/13C determinations in a sample of 34 Galactic clump stars as well as abundances of nitrogen, carbon and oxygen. Abundances of carbon were studied using the C2 Swan (0,1) band head at 5635.5 A. The wavelength interval 7980-8130 A with strong CN features was analysed in order to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 A. Compared with the Sun and dwarf stars of the Galactic disk, mean abundances in the investigated clump stars suggest that carbon is depleted by about 0.2 dex, nitrogen is enhanced by 0.2 dex and oxygen is close to abundances in dwarfs. Comparisons to evolutionary models show that the stars fall into two groups: the one is of first ascent giants with carbon isotope ratios altered according to the first dredge-up prediction, and the other one is of helium-core-burning stars with carbon isotope ratios altered by extra mixing. The stars investigated fall to these groups in approximately equal numbers.

Intracavity laser absorption spectroscopy of platinum sulfide in the near infrared

A new electronic transition of PtS with a red degraded band head at 12 460 cm −1 was recorded and analyzed. Gas phase PtS was produced in a platinum-lined hollow cathode with a trace of SF 6 gas, and the spectrum was recorded at near Doppler resolution using intracavity laser absorption spectroscopy. Molecular constants for the newly identified excited state are presented.

Chemical composition of clump stars in the open cluster NGC 6134★

We present an analysis of high-resolution spectra of six core-helium-burning ‘clump’ stars in the open cluster NGC 6134. Atmospheric parameters (Teff, log g, vt and [Fe/H]) were determined in our previous study by Carretta et al. (2004). In this study we present abundances of C, N, O and up to 24 other chemical elements. Abundances of carbon were derived using the C2 Swan (0,1) band head at 5635.5 Å (FEROS spectra) and the C2 Swan (1,0) band head at 4737 Å (UVES spectra). The wavelength interval 7980–8130 Å, with strong CN features, was analysed in order to determine nitrogen abundances and 12C/13C isotope ratios. The oxygen abundances were determined from the [O i] line at 6300 Å. Compared to the Sun and other dwarf stars of the Galactic disc, mean abundances in the investigated clump stars suggest that carbon is depleted by about 0.2 dex, nitrogen is overabundant by about 0.3 dex and oxygen is underabundant by about 0.1 dex. This has the effect of lowering the mean C/N ratio to 1.2 ± 0.2. The mean 12C/13C ratios are lowered to 9 ± 2.5. Concerning other chemical elements, the analysis of sodium and magnesium lines, lines of other α-elements, iron-group and heavier chemical elements gave abundance ratios close to the solar ones.

Product rotational Franck–Condon oscillations in HOD (Jka , kc ) dissociation

The technique of H(D) atom photofragment translation spectroscopy has been used to investigate the dissociation of jet-cooled HOD molecules following excitation to individual rovibrational levels of its (1B1) Rydberg state near 124 nm. Spectra have been recorded for both the D + OH and H + OD dissociation channels. The branching ratios between OH/OD(X , high v, low N), OH/OD(X , low v, high N), and OH/OD(A ) channels vary between different parent rotational levels, and between the OH and OD products. The variation between the OH and OD channels can be attributed to an isotopic mass effect on the rotational axes which influences non-adiabatic coupling strengths. In addition, there is a population alternation with product rotational quantum number N for the OH/OD(X, high v, low N) product, most striking for the OH case, the sense of which is correlated with the value of the parent pseudo-quantum number . It is shown that this is a consequence of recoil forces which lead to a closing of the HOD angle to near 90° accompanying non-adiabatic transfer from the state to the (1B1) state. The oscillation in population then derives from the symmetry properties around this angle of the product rotational wavefunctions. This suggests that the symmetry-induced population oscillation can only occur for a narrowly defined angular dissociation path. Model calculations also explain the different structure of the spin-orbit doubled low N band heads for each v(OH/OD) which also alternates for even and odd . The necessary conditions to observe these phenomena are discussed.

Ground and gamma band energy systematics in even xenon and barium nuclei

Rotation–vibration coupling parameter b at different spins is calculated on fitting the experimental energy for each nucleus in the framework of the General Asymmetric Rotor Model (Zhi. Phys. Rev. C, 51, 141 (1995)). Taking the even and odd spin energy sequences of the gamma band as separate bands besides the yrast band at large asymmetry (γ ≥ 20°), three values of the moment of inertia parameters a (ar, ae, and ao) are calculated from the band head energies. A striking correlation in a and b versus the product of the number of valance protons and neutrons (NpNn) is obtained. These trajectories and the γ versus NpNn correlation (Yan et al. Phys. Rev. C, 48, 1046 (1993)) are capable of predicting the unknown energies of the ground and gamma bands of even xenon and barium nuclei, knowing only an external parameter NpNn. This introduces the possibility of a simpler description of the structural evolution of these transitional nuclei.

High-resolution laser spectroscopy of the [formula omitted] transition of MgC 4H

The 0 0 0 band of the A ˜ 2 Π - X ˜ 2 Σ + transition of MgC 4H has been recorded at high resolution using laser-induced fluorescence. The molecules were produced using an ablation source by the reaction of magnesium and ∼10% acetylene seeded in helium. The rotationally-resolved high-resolution data were fitted to obtain rotational and fine structure parameters for both states. The centrifugal distortion, upper state Λ-doubling and ground state spin-rotation splitting parameters were all found to be negligible and the reasons for this are investigated and discussed. The 3 0 1 band heads of the A ˜ 2 Π - X ˜ 2 Σ + transition of MgC 6H were obtained but the rotational structure was not resolved.

Excited Electronic States of AuF

We have recorded laser excitation spectra of transitions from the ground X(1)Sigma(+) state of gaseous gold fluoride (AuF) into three excited electronic states in the visible region. We prepared the sample in a dc electric discharge by flowing a dilute mixture of SF(6) in argon through a hollow gold cathode. Two of these electronic states give rise to the previously reported yellow bands of the molecule, for which a rotational analysis is given here for the first time. We have analyzed the (0,0), (1,1), (0,1), and (1,2) bands of these two transitions, which we identify as [17.8]0(+)-X(1)Sigma(+) and [17.7]1-X(1)Sigma(+); their red-degraded (0,0) band heads lie at 563.0 and 566.2 nm, respectively. The (0,0) band of a new, red-degraded [14.0]1-X(1)Sigma(+) transition at 715.1 nm has also been recorded and analyzed. An accurate set of molecular constants of the three excited states as well as the ground state has been determined by least-squares fitting all of the optical data together with measurements made by other workers of the pure rotational spectrum of AuF in its ground state. These constants include the electronic term energies, vibrational frequencies, rotational constants, and Omega-doubling constants. We discuss the nature of these three excited electronic states in terms of the ionic Au(+)F(-) electronic configurations from which they are derived.

Electronic Spectra of C 6H + and C 6H 3+ in the Gas Phase

Measurement of the (3)Pi-(3)Pi transition of C(6)H(+) in the gas phase near 19486 cm(-1) is reported. The experiment was carried out with a supersonic slit-jet expansion discharge using cavity ringdown absorption spectroscopy. Partly resolved P lines and observation of band heads permitted a rotational contour fit. Spectroscopic constants in the ground and excited-state were determined. The density of ions being sampled is merely 2 x 10(8) cm(-3). Broadening of the spectral lines indicates the excited-state lifetime to be approximately 100 ps. The electronic transition of HC(6)H(2)(+) at 26402 cm(-1) assumed to be (1)A(1)-X (1)A(1) in C(2v) symmetry could not be rotationally resolved.