992 resultados para Essential Spectrum


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More data will be produced in the next five years than in the entire history of human kind, a digital deluge that marks the beginning of the Century of Information. Through a year-long consultation with UK researchers, a coherent strategy has been developed, which will nurture Century-of-Information Research (CIR); it crystallises the ideas developed by the e-Science Directors' Forum Strategy Working Group. This paper is an abridged version of their latest report which can be found at: http://wikis.nesc.ac.uk/escienvoy/Century_of_Information_Research_Strategy which also records the consultation process and the affiliations of the authors. This document is derived from a paper presented at the Oxford e-Research Conference 2008 and takes into account suggestions made in the ensuing panel discussion. The goals of the CIR Strategy are to facilitate the growth of UK research and innovation that is data and computationally intensive and to develop a new culture of 'digital-systems judgement' that will equip research communities, businesses, government and society as a whole, with the skills essential to compete and prosper in the Century of Information. The CIR Strategy identifies a national requirement for a balanced programme of coordination, research, infrastructure, translational investment and education to empower UK researchers, industry, government and society. The Strategy is designed to deliver an environment which meets the needs of UK researchers so that they can respond agilely to challenges, can create knowledge and skills, and can lead new kinds of research. It is a call to action for those engaged in research, those providing data and computational facilities, those governing research and those shaping education policies. The ultimate aim is to help researchers strengthen the international competitiveness of the UK research base and increase its contribution to the economy. The objectives of the Strategy are to better enable UK researchers across all disciplines to contribute world-leading fundamental research; to accelerate the translation of research into practice; and to develop improved capabilities, facilities and context for research and innovation. It envisages a culture that is better able to grasp the opportunities provided by the growing wealth of digital information. Computing has, of course, already become a fundamental tool in all research disciplines. The UK e-Science programme (2001-06)—since emulated internationally—pioneered the invention and use of new research methods, and a new wave of innovations in digital-information technologies which have enabled them. The Strategy argues that the UK must now harness and leverage its own, plus the now global, investment in digital-information technology in order to spread the benefits as widely as possible in research, education, industry and government. Implementing the Strategy would deliver the computational infrastructure and its benefits as envisaged in the Science & Innovation Investment Framework 2004-2014 (July 2004), and in the reports developing those proposals. To achieve this, the Strategy proposes the following actions: support the continuous innovation of digital-information research methods; provide easily used, pervasive and sustained e-Infrastructure for all research; enlarge the productive research community which exploits the new methods efficiently; generate capacity, propagate knowledge and develop skills via new curricula; and develop coordination mechanisms to improve the opportunities for interdisciplinary research and to make digital-infrastructure provision more cost effective. To gain the best value for money strategic coordination is required across a broad spectrum of stakeholders. A coherent strategy is essential in order to establish and sustain the UK as an international leader of well-curated national data assets and computational infrastructure, which is expertly used to shape policy, support decisions, empower researchers and to roll out the results to the wider benefit of society. The value of data as a foundation for wellbeing and a sustainable society must be appreciated; national resources must be more wisely directed to the collection, curation, discovery, widening access, analysis and exploitation of these data. Every researcher must be able to draw on skills, tools and computational resources to develop insights, test hypotheses and translate inventions into productive use, or to extract knowledge in support of governmental decision making. This foundation plus the skills developed will launch significant advances in research, in business, in professional practice and in government with many consequent benefits for UK citizens. The Strategy presented here addresses these complex and interlocking requirements.

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Rotational structure has been resolved and analyzed in two of the infrared‐active perpendicular bands of C2H4 vapor: the Type b fundamental band, ν10, at 826 cm—1, and the Type c fundamental band, ν7, at 949 cm—1. Many of the individual PP and RR branch lines have been observed. The analysis has been confined to values of the quantum number K≥3, for which energy levels ethylene shows no detectable deviations from a symmetric‐top rotational structure. The analysis reveals a Coriolis interaction between ν7 and ν10, and between ν4 and ν10, and values of the Coriolis constants ζ7,10z and ζ4,10y are obtained; these are related to normal coordinate calculations for the appropriate symmetry species, and force constants are derived to fit the observed zeta constants. The band center of ν10 has been revised from the original figure of 810 cm—1 to the new value, 826 cm—1, and the inactive frequency ν4 is estimated to lie at 1023±3 cm—1, in good agreement with the previous estimate of 1027 cm—1. The change in the value of ν10 leads to a suggested change in the value of the Raman‐active fundamental ν6 from 1236 to 1222 cm—1. New combination bands have been observed at 2174 cm—1, assigned as ν3+ν10; and at 2252 cm—1, assigned as ν4+ν6; also rotational structure has been resolved and analyzed in the ν6+ν10 band at 2048 cm—1. The new data obtained for the C2H4 molecule are summarized in Table XII, with all of the other data presently available on the vibrational and rotational constants.

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It is now possible to calculate the nine-dimensional rovibrational wavefunctions of sequentially bonded four-atom molecules variationally without dynamical approximation. In the case of HCCH, the simplest such molecule, many hundreds of rovibrational (J = 0, 1, 2) levels can be converged to better than 1.5 cm −1. Variational calculations of this kind are used here systematically to refine the well-known quartic valence-coordinate forcefleld of Strey and Mills [J.Mol. Spectrosc.59, 103-115 (1976)] against experimental term values up to three C-H stretch quanta for the principal and two deuterated isotopomers, yielding a new surface that reproduces the energies of all the known Σ, Π, and Δ states of these species up to the energy of two C-H stretch quanta with an rms error of 3 cm−1 . The refined forcefield is used to study the resonances associated with the accidental degeneracies (ν2 + ν4 + ν5, ν3) and (ν2 + 2ν5, ν1) in the principal isotopomer, leading to a clarification of the assignment of she experimentally detected states in the 2ν3 and 3ν3, polyads, and to the finding that vibrational Coriolis (kinetic energy) terms, rather than quartic anharmonicities in the potential, are the primary cause of the resonant interactions. Using a new cubic ab initio electric dipole field to calculate IR absorption coefficients, 24 undetected Σ and Π states of 1H12C12C1H and 5 undetected Σ states of D12C12CD are identified as candidates for experimental study, and their calculated energies and assignments are given.

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The microwave spectra of CHD2CN and CHD2NC have been measured from 18 to 40 GHz; about 20 type A and 30 type C transitions have been observed for each molecule. These have been fitted to a Hamiltonian using 3 rotational constants, and 5 quartic and 4 sextic distortion constants, in the IrS reduction of Watson [in “Vibrational spectra and structure” Vol. 6 (1977)]; the standard error of the fit is 26 kHz. For methyl cyanide the 5 quartic distortion constants have been used to further refine the recent harmonic force field of Duncan et al. [J. Mol. Spectrosc. 69, 123 (1978)], but the changes are small. Finally, for both molecules, the harmonic force field has been used to determine zero point average moments of inertia Iz from the ground state rotational constants for many isotopic species, and these have been used to determine an rz structure. The results are compared with rs structure calculations.

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The J + 1 ← J transitions (J = 2, 3, 4, 5, and 6) in the microwave spectrum of SiH3NCO have been assigned for the vibrational ground state and for the vibrational states v10 = 1, 2, and 3. The results for v10 = 0 confirm earlier work. The vibration-rotation constants show a remarkable variation with v10 and l10. To a large extent the anomalous behavior of these constants has been explained in terms of a strongly anharmonic potential function for the ν10 vibrational mode.

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High resolution infrared spectra of the ν9 and ν10 perpendicular fundamentals of the allene molecule are reported, in which the J structure in the sub-bands has been partially resolved. Analysis of the latter shows that the vibrational origin ν9 = 999 cm−1, some 35 cm−1 below previous assignments. The pronounced asymmetry in the intensity distribution of the rotational structure which this assignment implies is shown to be expected theoretically, due to the Coriolis perturbations involved, and it is interpreted in terms of the sign and magnitude of the ratio of the dipole moment derivatives in the two fundamentals. The results of this analysis are shown to be in good agreement with observations on allene-1.1-d2, where similar intensity perturbations are observed, and with an independent analysis of the ν8 band of allene-h4. The A rotational constant of allene-h4 is found to have the value 4.82 ± 0.01 cm−1, and for the molecular geometry we obtain r(CH) = 1.084 A, r(CC) = 1.308 A, and HCH = 118.4°. A partial analysis of the rotational structure of the hot bands (ν9 + ν11 − ν11) and (ν10 + ν11 − ν11) is presented; these provide an example of a strong Coriolis interaction between nearly degenerate A1A2 and B1B2 pairs of vibrational levels. Some localized rotational perturbations in the ν9 and ν10 fundamentals are also noted, and their possible interpretations are discussed.

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The microwave spectra of 2-aminopyridine-NH2, -ND2, and of both of the two possible -NHD molecules have been observed and assigned in the 0+ vibrational state of the amino group inversion vibration; the assignment for three of the molecules in the 0− state is also made. From intensity measurements the 0+-0− splitting is estimated to be 135 ± 25 cm−1 for the -NH2 molecule and 95 ± 30 cm−1 for the -ND2 molecule. The rotational constants are interpreted in terms of a structure in which the amino group is bent about 32° out of the molecular plane, the c coordinates of the two amino H atoms being 0.21 and 0.28 Å. Stark effect measurements give a dipole moment of about 0.9 D which is almost entirely in the b axis, and which changes quite significantly between the 0+ and 0− states.

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Infrared spectra of the trans and the cis isomers of nitrous acid, both HONO and DONO, have been observed in the gas phase using a Fourier transform interferometer with a resolution of about 0.05 cm−1 from 4000 to 500 cm−1. Rotational analyses are reported on eleven of the fundamentals and some overtones.

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The infrared spectrum of carbon suboxide has been recorded from 1800 to 2600 cm−1 at a resolution of 0.003 cm−1. About 7% of the ca. 40 000 lines observed have been assigned and analyzed, belonging to 36 different bands. Most of these are associated with the fundamental ν3, at 2289.80 cm−1, and the combination band ν2 + ν4, at 2386.61 cm−1, each of which give rise to a system of sum bands, difference bands, and hot bands involving the low-wave-number fundamental ν7 at 18 cm−1. A few other tentative assignments are made. The bands have been analyzed for vibrational and rotational constants.

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The infrared spectrum of the stretching fundamentals of SiF2 has been obtained at a resolution of ≈ 0.1 cm−1 using a FTIR spectrometer. The spectrum has been analysed using computer simulation based on a coupled hamiltonian for v1 and v3, giving v1 = 855.01 cm−1 and v3 = 870.40 cm−1. The relative magnitude and sign of the vibrational transition moments has been determined from the ξC13 Coriolis coupling.

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High‐resolution infrared spectra of B2H6 vapor are reported. The sample was prepared from the naturally occurring 11B☒10B isotopic mixture. The rotational structure of the infrared bands has been analysed for Coriolis perturbations due to rotation about the axis of least moment of inertia (the B⋅⋅⋅B axis). The following results have been obtained: (a) interaction between the Type A fundamental ν18 and the inactive fundamental ν5 has been observed, thus confirming the assignment of ν5 at 833 cm—1, giving ∣ ζ5,18Z ∣=0.55±0.05; (b) interaction observed between the Type A combination band (ν10+ν12) at 1283 cm—1 and the inactive combination (ν10+ν7) gives an estimate of the unobserved fundamental ν7 as 850±30 cm—1, and an estimate of ∣ ζ7,12Z ∣=0.6±0.1; (c) the absence of any observed perturbation of the Type C fundamental ν14 at 973 cm—1, suggests, by negative arguments, that either the unobserved fundamental ν9 does not lie in the frequency range 900 to 1100 cm—1, or ∣ ζ9,14Z ∣<0.2. The assignment of the unobserved fundamental vibrations of diborane is discussed in the light of this evidence.

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Previously published data on the vibrational fundamentals and overtones of the carbonyl stretching modes of Ni(CO)4 and Co(CO)3NO are reinterpreted using the recent model of Mills and Robiette, including Darling-Dennison resonances and local mode effects. The harmonic wavenumber θm and anharmonicity constant xm associated with the carbonyl and nitrosyl stretching modes are derived, and the 13C and 18O isotopic shifts are discussed in relation to the harmonic and anharmonic force field.

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Several high-order vibration-rotation perturbations in the high-resolution infrared spectrum of monofluoroacetylene, HCCF, are assigned and analyzed in detail. They result in avoided crossings in the rotational structure of several bands, and precise values for the effective high-order terms in the Hamiltonian have been determined. The significance of these results for intramolecular vibrational redistribution is discussed.