Band Head Research Articles

On the 0+ excited states in even-even deformed nuclei

The low-lying 0+ excited states remain an object of particular interest in the nuclear structure physics. Recently long sets of 0+ excited states were experimentally observed. Our analysis of the experimental data have shown that in even-even nuclei of the rare-earth and actinide regions the energies of all low lying 0+ excited states with great accuracy can be distributed on parabolic functions of the number of monopole excitations building these states. Along with the classification of the energies of the 0+ excited states in respect to the number of bosons that build the band heads we analyze the role of their collectivity in the structure and evolution of the yrast bands and the B(E2) transition probabilities within these bands. The experimental determination in 160Dy of the predicted in this way 0+ excited state with energy 0.6813 MeV is presented.

Franck-Condon factors and observed band strength distribution in the vibrational structure of the Ag2 D-X band system

Potential curves for the X1?g+ and D1?u+ states of three diatomic silver isotopomers, 107Ag2, 107Ag109Ag and 109Ag2, were determined from the best available molecular constants by the Rydberg-Klein-Rees method. From these potentials, Franck-Condon factors and band-origin wave numbers were computed, and the reliability of the obtained values was verified by comparison with the observed band strength distribution and the measured band origin positions in a previously recorded D-X spectrum. The ratios of the Franck-Condon factors to those of corresponding isotopic bands were found to be very close to unity, revealing only a very small isotopic effect on the Franck Condon factors of Ag2 D-X bands. The isotopic shifts of the calculated band origins agree well with previously measured displacements of band heads.

Microscopic study of low energy collective states in even-even nuclei: A prospective analysis of dynamical corrections to vibrational mass parameters

A systematic study of low energy nuclear structure at normal deformation has been carried out using the Generator Coordinate Method mapped onto a 5-Dimensional Collective quadrupole Hamiltonian (5DCH) by using the Gaussian Overlap Approximation (GCM-GOA). The collective space is spanned by Hartree Fock Bogoliubov (HFB) states under axial and triaxial quadrupole constraints deduced with the D1S Gogny force. In addition, our 5DCH includes the Thouless-Valatin dynamical corrections to its rotational kinetic terms. The work is described in detail elsewhere together with the corresponding comparisons with experimental data when it is available. Many properties show a satisfactory agreement with experiment, but there is an almost systematic overestimation of vibrational band head energies, which is the subject of the present paper. We show here the performance of the theory on related observables, and propose improvements of the theory to address the problem of the vibrational band heads. An important reason for the deficient is the treatment of vibrational inertial parameters. In particular, the theory needs to include the dynamical Thouless-Valatin corrections to the vibrational terms in the 5DCH. In present work, on the aim of a simple formula grounded by known symmetry rules within the 5DCH, these dynamical TV corrections are roughly estimated, allowing us to handle their possible effects in term of spectroscopic properties, to present a guess of the next model improvment, and to isolate some areas in the chart where states Inπ = 0+2, 2+2 or 2+3 seem to have important components out of the scope of a pure collective quadrupole approach.

THE GEMINI SPECTRAL LIBRARY OF NEAR-IR LATE-TYPE STELLAR TEMPLATES AND ITS APPLICATION FOR VELOCITY DISPERSION MEASUREMENTS

We present a spectroscopic library of late spectral type stellar templates in the near-IR range 2.15-2.42microns, at R=5300-5900 resolution, oriented to support stellar kinematics studies in external galaxies, such as the direct determination of the masses of supermassive black-holes in nearby active (or non-active) galaxies. The combination of high spectral resolution and state-of-the-art instrumentation available in 8-m class telescopes has made the analysis of circumnuclear stellar kinematics using the near-IR CO band heads one of the most used techniques for such studies, and this library aims to provide the supporting datasets required by the higher spectral resolution and larger spectral coverage currently achieved with modern near-IR spectrographs. Examples of the application for kinematical analysis are given for data obtained with two Gemini instruments, but the templates can be easily adjusted for use with other near-IR spectrographs at similar or lower resolution. The example datasets are also used to revisit the "template mismatch" effect and the dependence of the velocity dispersion values obtained from the fitting process with the characteristics of the stellar templates. The library is available in electronic form from the Gemini web pages (link above).

Classical Collision Spectrum of O + CO

The work of Noid et al. [ J. Chem. Phys. 1977 , 67 , 404 ] has shown that sharp molecular spectra can be obtained through a Fourier transform of the autocorrelation function of a classical trajectory. In the present work, we extend this idea to obtain a spectrum by Fourier transform of the dipole moment function of collision product trajectories. We show that this "classical collision spectrum" (CCS) is related to the cross section for creating the product times an Einstein A factor. As a test case, we analyze product CO trajectories obtained from O + CO collisions at 8 km/s and focus on the spectral resolution of the CCS. The CCS of these trajectories shows rich quantum-like features, including well-separated vibrational overtones and rotational band heads, which become more pronounced with particular trajectory weighting methods. For polyatomic cases, the hope is that the CCS can be deconvolved into ro-vibrational specific probabilities and cross sections for quasi-periodic trajectories, which would otherwise overlap in a conventional classical trajectory energy analysis. Chaotic trajectories are expected to broaden and decrease the achievable resolution of the CCS. Chaotic motion will therefore impact the ability to separate ro-vibrational specific cross sections, an issue that will be addressed in future work.

New Features of Shape Coexistence inSm152

Excited states in ;{152}Sm have been investigated with the ;{152}Sm(n,n;{'}gamma) reaction. The lowest four negative-parity band structures have been characterized in detail with respect to their absolute decay properties. Specifically, a new K;{pi} = 0;{-} band has been assigned with its 1;{-} band head at 1681 keV. This newly observed band has a remarkable similarity in its E1 transition rates for decay to the first excited K;{pi} = 0;{+} band at 684 keV to the lowest K;{pi} = 0;{-} band and its decay to the ground-state band. Based on these decay properties, as well as energy considerations, this new band is assigned as a K;{pi} = 0;{-} octupole excitation based on the K;{pi} = 0_{2};{+} state. An emerging pattern of repeating excitations built on the 0_{2};{+} level similar to those built on the ground state may indicate that ;{152}Sm is a complex example of shape coexistence rather than a critical point nucleus.

Emission enhancement using two orthogonal targets in double pulse laser-induced breakdown spectroscopy

The enhancement of emission intensity resulting from the interaction between two laser-induced plasmas on two orthogonal targets was investigated using double pulse laser-induced breakdown spectroscopy (LIBS) at 0.7 Pa, by means of time-resolved spectroscopy and fast photography. The results showed that the interaction between both plasmas improved carbon emission intensity in comparison to a single laser-induced plasma. For all the carbon lines of interest 477.2 nm (CI), 426.7 nm (CII), and 473.4 nm (C 2 Swan band head), the intensity enhancement showed a maximum at a delay between lasers in the range from 2 to 5 μs; moreover it increased with the fluence of the first laser. On the other hand, in the case of C 2 the intensity enhancement reached a maximum at 5 mm from the target; however it decreased with increasing fluence of the second laser. The largest intensity enhancement found was twofold for atomic species and sixfold for molecular species.

Determination of iodine via the spectrum of barium mono-iodide using high-resolution continuum source molecular absorption spectrometry in a graphite furnace

Molecular absorption spectra of the diatomic molecules AlI, GaI, InI, TlI, MgI, CaI, SrI and BaI, generated in a graphite furnace, were studied using a high-resolution echelle spectrometer with the aim of finding a simple, reliable and sensitive analytical method for the determination of iodine. Among them, the barium mono-iodide (BaI) was found to have the strongest absorption bands around 538 nm and 560 nm, each of them consisting of a series of well-resolved rotational lines with half-widths of about 40–50 pm. The strongest BaI line, the band head at 538.308 nm has been evaluated systematically for its analytical use for the determination of iodine. High concentrations of hydrochloric acid (or chloride), hydrofluoric acid (or fluoride), iron, potassium and sodium resulted in significant reduction of the BaI molecular absorption. Apart from this, no other serious spectral or non-spectral interference has been observed. Different chemical forms of iodine, such as iodide, iodate and organically bound iodine produced identical BaI absorption sensitivity. The detection limit for iodine was 600 pg, and the calibration curve was linear up to 250 ng iodine. Two real samples with different chemical forms of iodine were analyzed using the proposed method. One sample was an iodide pill with a specified iodide content of 200 mg, the other one was a thyroid hormone pill with a specified content of 63.5 mg. The results were in good or satisfactory agreement with those of independent methods, the potentiometric titration and the inductively coupled plasma time-of-flight mass spectrometry (ICP-ToF-MS); the deviations were 2% and 8% for the iodide and the thyroid hormone sample, respectively. The relative standard deviation of the analytical results ( n = 3) was below 2%.

Metallicity and photospheric abundances in field GKM giants and dwarfs

This paper deals with standard elemental abundances in late-type stars. By analysing high signal-to-noise ratio and high-resolution data we have found that dwarf stars have generally solar and below-solar abundances, and that all giants in our sample are indicated to be over-abundant at the present stage of the study. The dwarf stars match the evolutionary diagram for the age interval ∼0.3―10 Gyr. The star EQ Vir from the sample is found to have several signatures of activity: namely, a higher value of υ sin i (12 km s ―1 ), and emission in spectral lines such as Hα and Ca II. Furthermore, its pronounced TiO 7055-A band head indicates a slight inconsistency with its spectral type. The TiO band head signature has been estimated in the coolest stars in the sample. Also the measured radial velocities indicate possible binarity for some of the stars in the sample. Importantly, emergent radiation from stars is a present topic for debate with respect to the habitable zones of planetary systems.

Mapping neutron levels in theA~100region: Theν3/2+[411] band inZr103

A new rotational band has been identified in {sup 103}Zr with a proposed 3/2{sup +} band head located at 26.8 keV. Quasiparticle rotor model calculations performed in the present work suggest a {nu}3/2{sup +}[411] dominant configuration for this band. The calculations also indicate that {sup 103}Zr has axial prolate deformation.

Surface analysis of nitride layers formed on Fe‐based alloys through plasma nitride process

AbstractNitriding phenomena that occur on the surfaces of pure Fe and FeCr alloy (16 wt% Cr) samples were investigated. An Ar + N2 mixture‐gas glow‐discharge plasma was used so that surface nitriding could occur on a clean surface etched by Ar+ ion sputtering. In addition, the metal substrates were kept at a low temperature to suppress the diffusion of nitrogen. These plasma‐nitriding conditions enabled us to characterize the surface reaction between nitrogen radicals and the metal substrates. The emission characteristics of the band heads of the nitrogen molecule ion (N2+) and nitrogen molecule from the glow‐discharge plasma suggest that the active nitrogen molecule is probably the major nitriding reactant. AES and angle‐resolved XPS were used to characterize the thickness of the nitride layer and the concentration of elements and chemical species in the nitride layer. The thickness of the nitride layer did not depend on the metal substrate type. An oxide layer with a thickness of a few nanometers was formed on the top of the nitride layer during the nitriding process. The oxide layer consisted of several species of Nx‐Fey‐O, NO+, and NO2−. In the FeCr alloy sample, these oxide species could be reduced because chromium is preferentially nitrided. Copyright © 2009 John Wiley & Sons, Ltd.

High-spin states in neutron-rich 102Mo nucleus

High-spin states in neutron-rich 102Mo nucleus have been studied by measuring the prompt γ-rays in the spontaneous fission of 252Cf. The previous level scheme has been updated and some new levels and transitions are identified. The one-phonon γ-band is expanded and a band head level of the two-phonon γ-band is proposed. The systematic characteristics of yrast bands, one-phonon γ-bands, two-phonon γ-bands and quasi-particle bands in 102Mo, 104Mo and 106Mo are discussed.

Extended collective bands in neutron-rich 109Ru

Levels in the neutron-rich 109Ru have been studied by observing the prompt γ-rays following the spontaneous fission fragments of 252Cf. The ground state band and the negative parity bands have been confirmed and extended. A positive parity band with the band head level at 332.5 keV is newly identified and suggested as a single-neutron excitation band built on the 7/2+[404] Nilsson orbital. Some structural characteristics of these bands are discussed.

Neutron decay widths of excited states ofBe11

The two-neutron transfer reaction $^{9}\mathrm{Be}$($^{16}\mathrm{O}$, $^{14}\mathrm{O}$)$^{11}\mathrm{Be}$[$^{10}\mathrm{Be}$ $+n$] has been used to measure the branching ratios for the neutron decay of excited states of $^{11}\mathrm{Be}$. The $^{14}\mathrm{O}$ ejectile was detected by a Q3D spectrometer at forward angles. The energies and angles of the $^{10}\mathrm{Be}$ fragments of the decaying $^{11}\mathrm{Be}$${}^{*}$ recoil were measured in coincidence with the $^{14}\mathrm{O}$ ejectile using a double-sided silicon strip detector array at backward angles. This enabled a kinematic reconstruction of the reaction to be performed. Theoretical decay branch ratios were calculated using barrier penetrability factors and were compared to the measured ratios to provide information on the relative reduced widths of the states. The decay widths have been used to link states in $^{11}\mathrm{Be}$ with a common structure and structurally to states in the daughter nucleus $^{10}\mathrm{Be}$. The $3/{2}^{\ensuremath{-}} 8.82$-MeV state was identified as a candidate for a molecular band head.

TiO and VO broad band absorption features in the optical spectrum of the atmosphere of the hot-Jupiter HD 209458b

Context. The presence of titanium oxide (TiO) and vanadium oxide (VO) gas phase species is searched for in the atmosphere of the hot Jupiter HD 209458b. Aims. We compared a model for the planet’s transmitted spectrum to multi-wavelength eclipse-depth measurements (from 3 000 to 10 000 A), obtained by Sing et al. (2008a) using archived HST-STIS time series spectra. We make use of these observations to search for spectral signatures from extra absorbers in the planet a tmosphere between 6 000 and 8 000 A. Methods. Along with sodium depletion and Rayleigh scattering recently published for this exoplanet atmosphere, an extra absorb er of uncertain origin, redward of the sodium lines, resides in the atmosphere of the planet. Furthermore, this planet has a stratosphere experiencing a thermal inversion caused by the capture of optical stellar flux by absorbers that resides at altitude. Rec ent models have predicted that the presence of TiO and VO in the atmosphere of HD 209458b may be responsible for this temperature inversion. Although no specific TiO and VO spectral band head signatures have been identified unambiguously in the observed spectrum , we suggest here that the opacities of those molecules are possi ble candidates to explain the remaining continuous broad band absorption observed between 6 200 and 8 000 A. To match reasonably well the data, the abundances of TiO and VO molecules are evaluated from ten to one thousand times below solar. This upper limit result is in agreement with expected variations with altitude due to depletion effects such as condensation. Results.

Identification of new collective bands in neutron-richZr102

The level scheme of $^{102}\mathrm{Zr}$ has been expanded by measuring high-fold prompt $\ensuremath{\gamma}$-ray coincidence events in the spontaneous fission of $^{252}\mathrm{Cf}$ with the Gammasphere array. Previous identifications have been confirmed. A two-quasi-particle band with a band head energy of 2926.4 keV has been identified for the first time, as well as two rotational collective bands, with band head energies of 1386.3 and 1652.7 keV, respectively. Spins and parties are assigned based on level systematics and angular correlation measurements.

Linear polarization measurements and negative-parity states inSr80

High-spin states in $^{80}\mathrm{Sr}$ were studied using the ${}^{54}\mathrm{Fe}({}^{28}\mathrm{Si},2p)$ reaction at 90 MeV and the ${}^{58}\mathrm{Ni}({}^{28}\mathrm{Si},\ensuremath{\alpha}2p)$ reaction at 110 MeV. Prompt $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\gamma}$ coincidences were measured from the ${}^{54}\mathrm{Fe}({}^{28}\mathrm{Si},2p)$ reaction using an array of 10 Compton-suppressed Ge detectors. $\ensuremath{\gamma}$-ray linear polarizations were measured in both reactions using three clover detectors as Compton polarimeters. Negative parity has been conclusively assigned to one band and is favored for two others based on the polarization measurements and the observation of six new linking transitions between the bands near their band heads. This evidence supports a picture of strong mixing between low-lying states with negative parity, similar to what has been observed in $^{82}\mathrm{Sr}$. Directional correlation of oriented nuclei ratios support the spin assignments made in the most recent in-beam study.

Line shape of the far-wing beyond the band head of the CO 2ν3 band

Carbon dioxide is one of the most important trace gases in the terrestrial atmosphere. The spectral data required in remote sensing are the spectral parameter of each absorption line and a line shape model. This paper describes the absorption properties of CO 2 near 2400 cm −1; these properties are of interest to those in the atmospheric temperature sounding field. The shape of the far-wing of N 2- and O 2-broadened CO 2 lines was investigated in the 2200–2500 cm −1 spectral region in a temperature range of atmospheric interest (230–318 K). We focused on the higher rotational quantum number of the R-branch in the ν 3 band, where the effect of the far-wing is enhanced. The effect of the far-wing has been studied extensively by others, since the CO 2 ν 3 band is known to exhibit sub-Lorentzian behavior. Here, we show the observed spectra along with calculated spectra for five temperatures. We used first-order line-mixing and the χ-factor, which accounts for the effect of the far-wing, to create the calculated spectra. Our results provide new knowledge of quantum interference of the spectral line in the ν 3 band of CO 2.

Radial Velocities of Stars in the Galactic Center

We present results from K-band slit scan observations of a ~20'' × 20'' region of the Galactic center (GC) in two separate epochs more than 5 years apart. The high-resolution (R = λ/Δ λ ≥ 14,000) observations allow the most accurate radial velocity and acceleration measurements of the stars in the central parsec of the Galaxy. Detected stars can be divided into three groups based on the CO absorption band heads at ~2.2935 μm and the He II lines at ~2.0581 and ~2.112, 2.113 μm: cool, narrow-line hot, and broad-line hot. The radial velocities of the cool, late-type stars have approximately a symmetrical distribution with its center at ~–7.8 ± 10.3 km s−1 and a standard deviation ~113.7 ± 10.3 km s−1. Although our statistics are dominated by the brightest stars, we estimate a central black hole mass of (3.9 ± 1.1) × 106 M☉, consistent with current estimates from complete orbits of individual stars. Our surface density profile and the velocity dispersion of the late-type stars support the existence of a low-density region at the Galactic center suggested by earlier observations. Many hot, early-type stars show radial velocity changes higher than maximum values allowed by pure circular orbital motions around a central massive object, suggesting that the motions of these stars greatly deviate from circular orbital motions around the Galactic center. The correlation between the radial velocities of the early-type He I stars and their declination offsets from Sagittarius A* suggests that a systematic rotation is present for the early-type population. No figure rotation around the Galactic center for the late-type stars is supported by the new observations.

Hyperdeformed band in 36Ar populated in the 12C + 24Mg elastic scattering

The strongly oscillating angular distributions of the elastic scattering of 12C + 24Mg at energies around the Coulomb barrier (Ecm = 10.67 − 16.00 MeV) [1] were reproduced adding three Breit-Wigner resonance terms with J values of 6, 7 and 8 h respectively to the l = 6, 7 and 8 terms of the elastic S-matrix. The elastic scattering S-matrix was calculated using the double folding, deep, optical potential with non-local interaction, also called, Sao Paulo Potential [2]. All fifteen angular distributions could be well reproduced by the 3 resonances, located respectively at Ecm = 14.15, 15.8 and 16.9 MeV in the entrance channel, which correspond to excitation energies of 30.45, 32.1 and 33.2 MeV in the 36Ar compound nucleus. The J = 6, 7 and 8 h resonances fit well into a rotational molecular band, together with the J = 18, 20, 22 and 24 h resonances observed in the 16O + 20Ne elastic scattering [3]. The band head is at 29.5 MeV excitation energy in the 36Ar compound nucleus and has a large moment of inertia indicating a large deformation. Calculations of Rae and Merchant [4] propose the existence of a hyperdeformed band in 36Ar with 12C + 24Mg and 16O + 20Ne cluster structure.