Band Head Research Articles

Optical emission spectroscopy of the active species in nitrogen plasma

Optical emission spectroscopy is used to study the production of active species in nitrogen plasma excited by a 50 Hz pulsed-dc power source. The emission intensities of the band heads of the second positive (λ=337.1 nm; 0–0) and first negative (λ=391.4 nm; 0–0) systems are used to investigate the dependence of their radiative states N2(C 3Π u ) and population density on operating parameters. The emission intensity of the radiative state is used to determine the relative dependence of ion density on operating conditions by considering the fact that, in low-temperature plasmas, the dominant mechanism of the population of ) state starts from the ground state mainly by electron collisions. It is found that the production of these active species has a significant dependence on the discharge parameters and may be optimized under typical operating conditions.

Dynamical Properties of Ultraluminous Infrared Galaxies. I. Mass Ratio Conditions for ULIRG Activity in Interacting Pairs

We present first results from our Very Large Telescope large program to study the dynamical evolution of ultraluminous infrared galaxies (ULIRGs), which are the products of mergers of gas-rich galaxies. The full data set consists of high-resolution long-slit H- and K-band spectra of 38 ULIRGs and 12 QSOs (in the range 0.042 < z < 0.268). In this paper, we present the sources that have not fully coalesced and therefore have two distinct nuclei. This subsample consists of 21 ULIRGs, the nuclear separation of which varies between 1.6 and 23.3 kpc. From the CO band heads that appear in our spectra, we extract the stellar velocity dispersion, σ, and the rotational velocity, Vrot. The stellar dispersion equals 142 km s-1 on average, while Vrot is often of the same order. We combine our spectroscopic results with high-resolution infrared (IR) imaging data to study the conditions for ULIRG activity in interacting pairs. We find that the majority of ULIRGs are triggered by almost equal-mass major mergers of 1.5 : 1 average ratio. Less frequently, 3 : 1 encounters are also observed in our sample. However, less violent mergers of mass ratio >3 : 1 typically do not force enough gas into the center to generate ULIRG luminosities.

Spectral signature of native CN bonds for bacterium detection and identification using femtosecond laser-induced breakdown spectroscopy

A sample of Escherichia coli has been analyzed by laser-induced breakdown spectroscopy (LIBS) using femtosecond pulses. The spectrum shows strong CN molecular bands due to the direct ablation of native CN molecular bonds from the bacteria in contrast with weak atomic lines from carbon. The native nature of the observed CN bonds is supported by the kinetic behavior of the CN band head which rapidly decays with a time constant of 94 ns, while for a pure graphite sample the CN band head increases with a delay of 450 ns due to recombination with the ambient air. Moreover, about hundred resolved lines belonging to 12 atomic or molecular species are recorded, providing a valuable spectral signature to identify the bacterium.

Determination of non-metals via molecular absorption using high-resolution continuum source absorption spectrometry and graphite furnace atomization

This work describes investigations on the determination of the non-metals fluorine, chlorine, sulfur and phosphorus in a graphite furnace atomizer using high-resolution continuum source absorption spectrometry. With this technique, the general problem of limited accessibility to the non-metal resonance lines, all located in the vacuum ultraviolet wavelength region, could be avoided by evaluation of narrow-band molecular absorption in the ultraviolet spectral region. The absorption originates from diatomic molecules produced under certain conditions in the graphite atomizer in the presence of the element in question. In detail, an excess of the metals gallium and aluminium was used to convert fluorine and chlorine to their molecular forms GaF and AlCl, respectively. In a similar manner, sulfur could be converted to CS and phosphorus to PO molecules. For all species, narrow spectral structures, belonging to specific band heads or individual rotational lines, could be found at well-accessible wavelengths between 211 and 261 nm. Using these absorption structures, analytical parameters were evaluated for the determination of the four non-metals. The obtained values for the characteristic masses and the limits of detection are as follows: 13 pg and 9 pg for fluorine; 300 pg and 70 pg for chlorine; 12 ng and 2.3 ng for sulfur; 4.4 ng and 0.9 ng for phosphorus. All methods developed were confirmed by measurements on certified reference materials. In comparison to previous investigations with an air–acetylene flame system, an improvement of up to three orders of magnitude in the limits of detection was achieved.

Determination of phosphorus by molecular absorption of phosphorus monoxide using a high-resolution continuum source absorption spectrometer and an air–acetylene flame

PO molecular absorption bands, produced between 200 nm and 350 nm in an ordinary air–acetylene flame, were investigated using a high-resolution continuum source absorption spectrometer. The bands comprise sharp structures with half-widths similar to those of common atomic lines. Four PO band heads, located at 246.40 nm, 247.78 nm, 324.62 nm and 327.04 nm, were selected and systematically evaluated with regard to the determination of phosphorus. Nitric, sulfuric, hydrochloric and hydrofluoric acids, with concentrations of up to 5% (v/v), and up to 2000 mg L−1 solutions of Al, Co, Cr, Cu, Fe, K, Mn, Na, and Ni, were examined for possible matrix or spectral interferences. The only serious spectral interference found was the disturbance of the PO band head at 324.62 nm by the 324.754 nm Cu resonance line at high concentrations. Apart from this, a suppression effect on the PO absorption caused by the presence of Ca and Mg was observed and will be discussed in a separate paper in this journal. The determination of phosphorus via molecular PO absorption proved to be a rapid and reliable method. Performance was verified by analyses of standard reference materials, where good precision and accuracy were achieved. The limit of detection for phosphorus was found to be 1.3 mg L−1 for a measurement time of 25 s, using the PO band head at 324.62 nm. The linear dynamic range covers more than three orders of magnitude.

Spectroscopic optimization of abnormal glow conditions for plasma ion nitriding

Optical emission spectroscopy is used to characterize the production of active species as a function of hydrogen concentration in the mixture under different operating conditions. A major concern is to enhance the concentration of the active species by hydrogen addition that carry several electron volts energy above their ground states, and thus affect the surface chemistry. The emission intensity of the selected optical transitions of molecular and atomic species is measured to determine the functional dependence of their radiative states. The relative ground state molecular ion density [N 2 + ] is measured from the emission intensity of the first negative band head ( λ = 391.4 nm, 0–0) by considering the fact that in low temperature plasma, ion with single charge is produced by the electron impact, and the ion density is proportional to the electron density. It is found that the concentration of the active species may be enhanced significantly by selecting an appropriate gas composition and operating parameters. The SS-304 samples are nitrided under the optimum conditions for 4, 8, 12 and 16 hours and hardness values are found to increase five times for 16 hours treatment time. The optimized discharge conditions are found favorable for plasma ion nitriding.

New low-energy levels calculation for 155Eu

We have revisited the low-energy calculation of odd Z 155Eu in the frame of a semi-microscopic formalism as a support for the interpretation of the experimental results for the multipole mixing ratios of some electromagnetic transitions. The deformation parameters were obtained through a macroscopic-microscopic method, and the proton single particle levels, calculated with realistic Woods-Saxon potential were used as input in a quasi-particle calculation of the first few rotational band heads in the Lipkin-Nogami BCS aproximation. A better agreement is found between the experimental and calculated band heads if compared with previous evaluations and RIPL recommended values.

The spatial distribution of the temperatures and the emitted spectrum in the electrolyte cathode atmospheric glow discharge

In an electrolyte cathode atmospheric glow discharge (ELCAD), the gas temperature (Tgas) obtained from the intensity ratio of the OH 306–309 nm unresolved rotational band heads and the electron temperature (Tel) received from the intensity ratio of the Cu I 510.5 and 515.3 nm were investigated. In the near anode region, Tgas ≈ Tel ≈ 6000 K; in the positive column, Tgas ≈ 4000 K, Tel ≈ 5500 K; in the near cathode region, Tgas ≈ 8000 K, Tel ≈ 7500 K were found. These temperatures agree with our earlier results and are in accordance with the literature; that is, at atmospheric pressure, the gas and the electron temperatures approximate well with each other. The spatial intensity distribution of the atomic lines of metals dissolved in the electrolyte was measured and the intensity maximum occurred in the negative glow due to the high electron temperature and thus to the high excitation rate of this region.

Gemini Near Infrared Spectrograph Observations of the Central Supermassive Black Hole in Centaurus A

The Gemini Near Infrared Spectrograph on Gemini South unlocks new possibilities to study the central black holes (BHs) in dusty galaxies that have been inaccessible to previous BH studies. We exploit good near-infrared seeing to measure the central BH of Centaurus A (NGC 5128). We measure the stellar kinematics of NGC 5128 using the region around the CO band heads at 2.3 μm and determine the BH mass using axisymmetric orbit-based models. BHs are believed to be essential components of galaxies, and their evolutionary states appear to be closely linked to those of their hosts. Our current knowledge does not go much beyond this; galaxies such as NGC 5128 (a recent merger with an active galactic nucleus) can further develop this knowledge. However, NGC 5128 and galaxies like it contain large amounts of dust, which hamper optical spectroscopy, making near-infrared measurements an attractive alternative. We find a BH mass of 2.4 × 108 M⊙ for an edge-on model, 1.8 × 108 M⊙ for a model with an inclination of 45°, and 1.5 × 108 M⊙ for a model with an inclination of 20°. We adopt the value for the edge-on model, since it has significantly lower χ2; however, it is unlikely that we can constrain the actual inclination of moderately triaxial NGC 5128 using an axisymmetric modeling procedure. These estimates, based on adjusting the asymmetric kinematics of NGC 5128 so that we can use an axisymmetric code, are consistent with the range of acceptable BH masses implied by a previous gas dynamical study. However, these estimates are 5–10 times higher than that predicted by the correlation between BH mass and velocity dispersion. If NGC 5128 will eventually follow the trend for quiescent galaxies, this result suggests that its BH assembled first before its host component. NGC 5128 thus provides an important example for our knowledge of central BHs; this technique can be applied to other such galaxies to further explore this question.

Chemical composition of evolved stars in the open cluster NGC 7789

High-resolution spectra of six giants and three core-helium-burning “clump” stars in the open cluster NGC 7789 have been obtained with the SOFIN spectrograph on the Nordic Optical Telescope to investigate abundances of up to 20 chemical elements. Abundances of carbon were studied using the Swan (0, 1) band head at 5635.5 Å. The wavelength interval 7980–8130 Å with strong CN features was analysed in order to determine nitrogen abundances and isotope ratios. The oxygen abundances were determined from the [O I] line at 6300 Å. The overall metallicity of evolved stars in the cluster was found to be close to solar (). Compared with the Sun and other dwarf stars of the Galactic disk, mean abundances in the investigated giant stars suggest that carbon is depleted by about 0.2 dex, and nitrogen and oxygen are close to solar. In the clump stars investigated, carbon is depleted by about 0.2 dex, the mean abundance of nitrogen is enhanced by 0.26 dex and oxygen is lower by 0.14 dex. This has the effect of lowering the mean C/N ratios to the value of in the giant stars and to the value of in the clump stars. The mean ratios are lowered to about the same value of in the giants and clump stars investigated. Concerning other chemical elements an overabundance of sodium is noticeable and of silicon and calcium one is suspected. Abundances of iron-group and heavier chemical elements in all nine stars were found to be close to solar.

Probing the Dust Obscuration in Seyfert Galaxies using Infrared Spectroscopy. II. Implication for the Unification of Seyfert Galaxies

We report near-IR spectroscopic observations of 11 Seyfert galaxies (six Seyfert 1s, one Seyfert 1.9, and four Seyfert 2s) and additional galaxies (four LINERs, two H II, and one type 2 transition) for comparison, obtained using the Gemini twin-channel near-IR camera on the Shane 3 m telescope at Lick Observatory. With the unique design of the Gemini camera, full J and K spectra were taken simultaneously through the same slit. This produced accurate line ratios of hydrogen recombination lines over a large wavelength baseline. For the Seyfert 1s (≤1.5), the line ratios of Paβ/Brγ are not only comparable in both broad- and narrow-line regions but also consistent with case B recombination, indicating little or no reddening in both narrow- and broad-line regions. Seyfert 2 (>1.5) galaxies, however, show substantial reddening toward the narrow-line regions. We compare optical reddening data from the literature and find significant support for the dichotomy between Seyfert 1s and Seyfert 2s, at least in low-luminosity objects. Two different scenarios are explored to explain the observed difference in reddening: a difference in reddening due to an extended dusty torus under active galactic nucleus unification, and a difference due to a different grain size distribution between the two Seyfert types. We also discuss a similar potential difference found in the strength of the 9.7 μm silicate line, along with a possible correlation between the narrow-line reddening and the strength of the silicate absorption line. We also analyzed CO band head absorption features longward of 2.3 μm to look for nonstellar contamination and evidence of recent star formation activity. The CO band head in Seyfert 1s shows heavy contamination from nonstellar radiation, which is correlated with an H - K nuclear color excess. We confirm that the CO spectroscopic indices in both Seyfert types do not show evidence of recent star formation. Taking the nonstellar contamination into account, there is little evidence from the CO index for a difference in star formation rates in the nuclei of Seyfert 1s and Seyfert 2s in our low-luminosity sample.

Spectral line parameters in the (3 ← 0) overtone band of the HI molecule and line-mixing in the band head

The linestrengths, self-pressure broadening and shifting coefficients have been measured for P 3 (10)– R 3 (12) lines in the second overtone band of hydrogen iodide. A dipole moment function in terms of the reduced nuclear displacement x = ( R − R e )/ R e is obtained using rotationless dipole matrix elements determined by the Herman–Wallis analysis of the (1, 2, 3 ← 0) HI bands: μ ( x) = 0.4471(5) − 0.0770(2) x + 0.547(3) x 2 − 1.93(2) x 3, in a full agreement with the function proposed previously [J. Mol. Spectrosc. 223 (2004) 67]. A close match is demonstrated of the results of most recent relativistic calculations [Phys. Chem. Chem. Phys. 6 (2004) 3779] with the spectroscopically derived electric dipole parameters for HI. Line-mixing in the band head is observed, the self-pressure shifting and broadening coefficients for the (3 ← 0) band lines are determined.

Plasma characterization of pulsed-laser ablation process used for fullerene-like CNx thin film deposition

An in situ Optical Emission Spectroscopy (OES) characterization was performed on Pulsed-Laser Ablation (PLA) process used for fullerene-like CNx thin film deposition at nitrogen pressures within the 5 ‐ 100 mTorr range. Plumes were generated by ablation of pyrolytic graphite (99.99%) target using a (500 mJ, 7 ns, 1064 nm) Nd: YAG-pulsed laser. The spectra from the plume show, essentially, the presence of the band heads of CN Violet vibrational/rotational B 2 § + - X 2 § + system and the characteristic C2 emission lines, belonging to the Swan A 3 ƒg - X ’ 3 ƒu system. These excited CN and C2 molecules were generated by laser ablation and by collisions of the plume with the substrate surface. Their vibrational temperatures were strongly dependent on nitrogen pressure during the deposition process and presented a decrease between 2.64 and 1.23 eV, as pressure increased from 5 to 100 mTorr. Synthesis of fullerene-like structures required high molecular temperatures at the condensation surface. High concentrations of CN radicals in the plasma promoted nitrogen incorporation into the films. The OES plasma characterization allowed for a correlation of the concentration and vibrational temperatures of CN and C2 species present in the plasma with the fullerene-like CNx film composition and bonding, determined by XPS, IR, and Raman spectroscopy.

Embryonic expression pattern of the Drosophila Kallmann syndrome gene kal-1

The role of kal-1, the gene responsible for the X chromosome-linked form of Kallmann syndrome, is not well definite. In Drosophila, the kal-1 gene encodes a putative protein with the characteristic kal-1 topology but with only two Fibronectin-like type III (FnIII) domains. We studied the embryonic expression pattern of kal-1 using whole mount in situ hybridization. This gene is expressed in the second half of embryogenesis showing a complex and dynamic pattern. kal-1 is expressed during important morphogenetic processes such as germ band retraction, dorsal closure and head involution. We found expression in cells associated with different sensory organs, such as the antennal organ, which has an olfactory function, the chordotonal organ, the Keilin's organ and the dorsal pharyngeal organ. Expression of kal-1 in the head also regards some ectodermal cells of the gnathal lobes. By studying the expression in Dfd and cnc homeotic mutants, we found that these ectodermal cells derive from the anterior and posterior mandibular segment, whose determination depends on cnc, and that the expression in the posterior mandibular segment requires Dfd activity. kal-1 is also expressed in the posterior part of the male gonads in a specific subset of the somatic cells called male-specific somatic gonadal precursors (msSGPs). This is the first time that the expression of a kal-1 ortholog has been demonstrated to be sex specific making the kal-1 transcript a useful tool for the study of sex determination in the gonad.

Characterization of an inductively coupled N2 plasma using sensitive diode laser spectroscopy

In this paper, we present an optical study of the state of N2 produced in an inductively coupled plasma. The operation of the discharge was characterized using ion flux measurements and broadband optical emission, and a clear change from capacitively to inductively coupled behaviour was observed with increasing applied power. The typical ion flux at 100 W and 10 mTorr was found to be 1.8 × 1018 m2 s−1, from which a ion density of ∼1.5 × 109 cm−3 was inferred. Diode laser cavity enhanced absorption spectroscopy (CEAS) was used to probe the state via the band at 686 nm. P33 band head spectra were used to determine both the translational (Ttr) and rotational (Trot) temperatures of the molecules at the v = 0 level. These were found to be in equilibrium but dependent on plasma parameters; in a 10 mTorr discharge, Trot ≈ Ttr, varying from ∼300 K at 5 W to ∼450 K at 400 W applied power. Absolute number densities in individual spin–rotation states were determined by calibrating the CEAS technique using the cavity ringdown time to measure the mirror reflectivity. The overall population in the v = 0 level was found to be (1.19 ± 0.07) × 1010 cm−3 under typical conditions of 100 W radio frequency power and 10 mTorr pressure, corresponding to a discharge efficiency for the production of this level of ∼10−5. A kinetic scheme is presented to account for the pressure and power dependence of the A-state concentration in the v = 0 level.

Rotational energy transfer in NO (A 2Sigma+,v'=0) by N2 and O2 at room temperature.

State-to-state rotational energy transfer (RET) rate coefficients for NO (A 2Sigma+, v'=0, J=5.5, 11.5, 17.5) were measured for N2 and O2 at room temperature using a pump-probe method. The NO A 2Sigma+ state is prepared by 226 nm light and the RET is monitored by fluorescence from the D 2Sigma+ v'=0 state, following excitation by a time-delayed laser at approximately 1.1 microm. Additionally, total collisional removal and final state distributions were measured exciting in the Q1+P21 band head, to simulate an NO laser-induced fluorescence atmospheric monitoring scheme. Time-resolved modeling is used to understand relaxation mechanisms and predict relaxation times in ambient air. H2O at atmospherically relevant concentrations does not affect the degree of RET in ambient air.

Absolute silicon monoxide density measurement by self-absorbed spectroscopy in a non-thermal atmospheric plasma

In this study we have estimated the density of SiO molecules produced in atmospheric dielectric barrier discharges by means of spectroscopic investigations based on the self-absorption diagnostic. The (2, 0), (1, 0) and (0, 0) ro-vibrational bands of the SiO(A 1Π–X 1Σ+) electronic transition were investigated. The effective values of Einstein coefficients and absorption cross sections for the considered rotational transitions were calculated. The SiO concentration during the plasma phase was estimated by comparisons between experimental and computed spectra for the three explored bands. For example, the estimated value was (5 ± 1) × 1013 cm−3, for (Ar/SiH4/N2O) = (98.43%/0.38%/1.19%). The conversion rate from silane to silicon monoxide was deduced as a function of silane fraction. The influence of the molecular fraction on the rotational temperature was investigated. A simple technique based on the ratio of band heads was presented as a useful tool, in order to roughly estimate the density of SiO.

High-spin states inAu179: Spectroscopy of shape-driving orbitals beyond the neutron midshell

Multiple band structures in Au179 are established from γ-ray spectroscopic measurements with Gammasphere at the Argonne Fragment Mass Analyzer. The yrast band, based on the 13∕2+ proton, confirms the predicted drop in excitation energy of the prolate deformed band head as compared to the heavier isotopes. The implications for the prolate energy minimum in odd-mass Au nuclei beyond the neutron i13∕2 midshell (N<102) are discussed.2 MoreReceived 2 February 2004DOI:https://doi.org/10.1103/PhysRevC.69.064315©2004 American Physical Society

IRAS 05436-0007 and the Emergence of M c Neil's Nebula

We present a study of McNeil's Nebula, a newly appeared reflection nebula in the L1630 cloud, together with photometry and spectroscopy of its source. New IR photometry compared with earlier Two Micron All Sky Survey data shows that the star has brightened by about 3 mag in the near-infrared, changing its location in a J-H/H-K' diagram precisely along a reddening vector. A Gemini Near InfraRed Imager K-band spectrum shows strong CO band head emission, and Brγ is in emission, indicative of strong accretion. A Gemini Multi-Object Spectrograph optical spectrum shows only a red, heavily veiled continuum, with Hα strongly in emission and displaying a pronounced P Cygni profile, with an absorption trough reaching velocities up to 600 km s-1. This implies significant mass loss in a powerful wind. However, no evidence is found for any shocks, as commonly seen in collimated outflows from young stars. Apparently the eruption has dispersed a layer of extinction, and this, together with the intrinsic brightening of the IRAS source, has allowed an earlier outflow cavity to be flooded with light, thus creating McNeil's Nebula.

An Infrared Spectroscopic Study of Eight Galactic Globular Clusters

We have obtained medium-resolution infrared K-band spectra of 44 giants in seven heavily reddened clusters in the Galactic bulge, as well as 12 giants in ω Centauri. We measure the equivalent widths of the Na doublet, the Ca triplet, and the CO band head, and then apply the new technique of Frogel et al. to determine the metallicity of each star. Averaging these values, we estimate the metallicity for each cluster and compare our new [Fe/H] values with previous determinations from the literature. Our estimates for each cluster are NGC 6256 (-1.35), NGC 6539 (-0.79), HP 1 (-1.30), Liller 1 (-0.36), Palomar 6 (-0.52), Terzan 2 (-0.87), and Terzan 4 (-1.62). We briefly discuss differences between the various [Fe/H] scales on which it was possible to base our calibration, which is found to be the largest uncertainty in using this technique to determine metallicities.