1,720,989 research outputs found
The infrared spectrum of (C2H2)-C-13 in the 60-2600 cm(-1) region: bending states up to nu(4) + nu(5)=4
No full textThe vibration-rotation spectra of C-13 substituted acetylene, (C2H2)-C-13, have been recorded in the region between 60 and 2600 cm(-1) at an effective resolution ranging from 0.001 to 0.006 cm(-1). Three different instruments were used to collect the experimental data in the extended spectral interval investigated. In total 9529 rotation vibration transitions have been assigned to 101 bands involving the bending states up to nu(tot) = nu(4) + nu(5) = 4, allowing the characterization of the ground state and of 33 vibrationally excited states. All the bands involving states up to nu(tot) = 3 have been analyzed simultaneously by adopting a model Hamiltonian which takes into account the vibration and rotation l-type resonances. The derived spectroscopic parameters reproduce the transition wavenumbers with a RMS value of the order of the experimental uncertainty. Using the same model, larger discrepancies between observed and calculated values have been obtained for transitions involving states with nu(tot) = 4. These could be satisfactorily reproduced only by adopting a set of effective constants for each vibrational manifold, in addition to the previously determined parameters, which were constrained in the analysis
Mono- and di-deuterated ammonias: Far-infrared spectra and spectroscopic parameters in the ground state
No full textTransitions of NH2D and ND2H have been detected in the high resolution spectrum of 14ND3 recorded at unapodized resolution of 0.00096 cm−1 in the region 60–600 cm−1 using the Bruker IFS 125 Fourier transform spectrometer located at the synchrotron far-infrared beamline, Canadian Light Source. In this study we report on the observation and analysis of the spectrum for the ground state of NH2D and ND2H. 2153 rotation and rotation-inversion transitions, with J up to 24, were assigned for NH2D, and 3214 transitions, with J up to 28, for ND2H. The newly assigned transitions, together with those present in the literature, were fitted on the basis of a Watson-type S reduced Hamiltonian using the IIIr and IIIl representations for NH2D and ND2H, respectively. The model Hamiltonian includes terms up to the 10th power of the angular momentum and vibration–rotation interaction terms between the inversion states. Precise and extended sets of spectroscopic effective parameters were derived for both isotopologues as results of least squares weighted fit procedures that reproduce the transition wavenumbers at experimental accuracy
Spectroscopic characterization of the v2 = 3 and v2 = v4 = 1 states for 15NH3 from high resolution infrared spectra
Full text linkThe a, s inversion levels of v2 = 3 and v2 = v4 = 1 vibration states of 15NH3 are studied from high resolution infrared spectra up to 3200 cm−1. Spectra were recorded from 60 to 2000 cm−1 using the Bruker IFS 125 interferometer located at the Canadian Light Source and from 1900 to 3200 cm−1 using the Bomem DA 008 in Bologna. Transitions in 3ν2 and ν2+ν4, in the 3ν2 ← ν2, ν2+ν4 ← ν2, 3ν2 ← 2ν2, ν2+ν4 ← 2ν2, 3ν2 ← ν4, ν2+ν4 ← ν4, and 3ν2 ↔ ν2+ν4 hot bands, and the rotation-inversion transitions in 3ν2 and ν2+ν4 have been observed. 5770 transitions with Jmax′/Kmax′ up to 15 have been assigned, including 395 perturbation allowed ones. All transitions were fitted simultaneously on the basis of a rotation-inversion Hamiltonian which includes distortion constants up to 10th power in the angular momentum and all symmetry allowed interaction parameters between and within the a, s inversion levels of v2 = 3 and v2 = v4 = 1. The term values of the lower levels of transitions have been calculated using the parameters recently derived for the ground and v2 = 1, 2 and v4 = 1 states. The data were reproduced at experimental accuracy. The results are compared with those of 14NH3. The experimental transitions are compared with their theoretically predicted values. The list of assignments is supplied as supplementary material. The present results noticeably improve the wavenumber line list in the HITRAN 2016 data base
High-resolution synchrotron-based Fourier transform spectroscopy of CH317OH in the 120-350 cm-1 far-infrared region
No full textThe Fourier transform spectrum of the [image omitted] isotopologue of methanol has been recorded in the 120-350 cm-1 far-infrared region at a resolution of 0.00096 cm-1 using synchrotron source radiation at the Canadian Light Source. The study, motivated by astrophysical applications, is aimed at generating a sufficiently accurate set of energy level term values for the ground vibrational state to allow prediction of the centres of the quadrupole hyperfine multiplets for astronomically observable sub-millimetre transitions to within an uncertainty of a few MHz. To expedite transition identification, a new function was added to the Ritz program in which predicted spectral line positions were generated by an adjustable interpolation between the known assignments for the [image omitted] and [image omitted] isotopologues. By displaying the predictions along with the experimental spectrum on the computer monitor and adjusting the predictions to match observed features, rapid assignment of numerous [image omitted] sub-bands was possible. The least squares function of the Ritz program was then used to generate term values for the identified levels. For each torsion-K-rotation substate, the term values were fitted to a Taylor-series expansion in powers of J(J + 1) to determine the substate origin energy and effective B-value. In this first phase of the study we did not attempt a full global fit to the assigned transitions, but instead fitted the sub-band J-independent origins to a restricted Hamiltonian containing the principal torsional and K-dependent terms. These included structural and torsional potential parameters plus quartic distortional and torsion-rotation interaction terms
Fourier transform synchrotron spectroscopy of torsional and CO-stretching bands of CH(3)(17)OH
No full textThe Fourier transform spectrum of the CH(3)(17)OH isotopologue of methanol has been recorded in the 65-1200 cm(-1) spectral region at a resolution of 0.00096 cm(-1) using synchrotron source radiation at the Canadian Light Source. Here we present an extension to higher torsional states of our investigation of the torsion-rotation transitions within the small-amplitude vibrational ground state, now including assignments of more than 16 500 lines involving quantum numbers in the ranges v(t) <= 3, J <= 30 and vertical bar K vertical bar <= 12, as well as a study of the strong CO-stretching band centered at 1020 cm(-1). Energy term values have been determined for assigned ground and CO-stretching levels by use of the Ritz program, and have been fitted to series expansions in powers of J(J + 1) to determine substate origins and effective B values. Several Fermi anharmonic and Coriolis level-crossing resonances coupling the CO stretch with high torsional ground-state levels have been identified and characterized. The study is motivated by astrophysical applications, with a principal aim being the compilation of an extensive set of energy term values to permit prediction of astronomically observable sub-millimetre transitions to within an uncertainty of a few MHz. (C) 2011 Elsevier Inc. All rights reserved
Fourier transform spectroscopy of the CO-stretching band of O-18 methanol
No full textThe high-resolution Fourier transform spectrum of the nu(8) CO-stretching band of CH(3)(18)OH between 900 and 1100 cm(-1) has been recorded at the Canadian Light Source (CLS) synchrotron facility in Saskatoon, and the majority of the torsion-rotation structure has been analyzed. For the nu(t) = 0 torsional ground state. subbands have been identified for K values from 0 to 11 for A and E torsional symmetries up to J values typically well over 30. For nu(t) = 1, A and E subbands have been assigned up to K = 7, and several v, = 2 subbands have also been identified. Upper-state term values determined from the assigned transitions using the Ritz program have been fitted to J(J + 1) power-series expansions to obtain substate Origins and sets of state-specific parameters giving a compact representation of the substate J-dependence. The nu(t) = 0 subband origins have been fitted to effective molecular constants for the excited CO-stretching state and a torsional barrier of 377.49(32) cm(-1) is found, representing a 0.89% increase over the ground-state value. The vibrational energy for the CO-stretch state was found to be 1007.49(7) cm(-1). A number of subband-wide and J-localized perturbations have been seen in the spectrum, arising both from anharmonic and Coriolis interactions, and several of the interacting states have been identified. (C) 2009 Elsevier Inc. All rights reserved
The v2 = 1, 2 and v4 = 1 bending states of 15NH3 and their analysis at experimental accuracy
No full text15NH3 is the object of extensive investigation due to the central role of ammonia in astronomical sciences and to the complexity of modeling its interacting vibrationally-excited states. Of major interest in astrochemistry is the determination of the 14N/15N ratio in Space, characterized by unexpected variability among different Solar System objects and reservoirs. Recently, the spectroscopic analysis of ground and v2 = 1 a, s states of 15NH3 has been completed at experimental accuracy. Here the characterization of the a, s inversion symmetry levels of v2 = 1, 2 and v4 = 1 states is presented. New spectra of 15NH3 have been recorded from 325 to 2000 cm1 at a resolution ranging from 0.00096 cm1 to 0.003 cm1 , using the Canadian Light Source synchrotron at CLS. 7518 transitions covering nine bands, nu2, 2nu2, nu4, 2nu2 - nu2, nu4 -nu2, 2nu2- nu4 and the inversion-rotation transitions in the excited states, have been fitted simultaneously. The effective Hamiltonian adopted includes all symmetry allowed interactions between and within the studied excited states, according to the most recent results on ammonia. The transitions have been reproduced at experimental accuracy using 185 spectroscopic parameters, determined with high precision. The leading diagonal parameters, Gv, B, C, D’s, compare well with those of 14NH3. The wavenumbers of the assigned transitions are compared with their theoretically predicted values. An improved set of ground state parameters is also derived. These results improve noticeably the wavenumber line list in the HITRAN data base
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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