Quasi-linearity in HCCN: effects of the v2 fundamental

Miller, Charles E.; Eckhoff, W. C.; Curl, R. F.

doi:10.1016/0022-2860(94)08512-g

Cited by 17 publications

(24 citation statements)

References 20 publications

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“…With respect to the experimental HC1 bond distance, Brown et al 22 found that this bond is shorter than all known C-H bond lengths previously determined in other hydrocarbon molecules, suggesting that an accurate study was necessary to understand the HCCN structure. However, they obtained this short CH bond distance by assuming a linear structure, but later studies have shown that the triplet ground state of HCCN is best viewed as quasilinear [23][24][25][26][27][28][29] , and our results support that conclusion.…”

Section: A Equilibrium Structures Harmonic Frequencies and Equilibrsupporting

confidence: 82%

“…al slightly modified their previous experimental conclusion based on a microwave study, suggesting a quasilinear structure instead of a strict linear one 22 . More experimental evidence for the quasilinearity of cyanocarbene came from analysis of high-resolution rotational 23 and vibrational [24][25][26][27][28][29] spectra. McCarthy and co-workers 23 estimated the transition energies from relative intensity measurements in the microwave region.…”

Section: Introductionmentioning

confidence: 99%

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Accurate ab initio quartic force fields of cyclic and bent HC2N isomers

Inostroza

Huang

Lee

2011

The Journal of Chemical Physics

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Highly correlated ab initio quartic force field (QFFs) are used to calculate the equilibrium structures and predict the spectroscopic parameters of three HC 2 N isomers. Specifically, the ground state quasilinear triplet and the lowest cyclic and bent singlet isomers are included in the present study.Extensive treatment of correlation effects were included using the singles and doubles coupled-cluster method that includes a perturbational estimate of the effects of connected triple excitations, denoted CCSD(T). Dunning's correlation-consistent basis sets cc-pVXZ, X=3,4,5, were used, and a three-point formula for extrapolation to the one-particle basis set limit was used. Core-correlation and scalar relativistic corrections were also included to yield highly accurate QFFs. The QFFs were used together with second-order perturbation theory (with proper treatment of Fermi resonances) and variational methods to solve the nuclear Schrödinger equation. The quasilinear nature of the triplet isomer is problematic, and it is concluded that a QFF is not adequate to describe properly all of the fundamental vibrational frequencies and spectroscopic constants (though some constants not dependent on the bending motion are well reproduced by perturbation theory). On the other hand, this procedure (a QFF together with either perturbation theory or variational methods) leads to highly accurate fundamental vibrational frequencies and spectroscopic constants for the cyclic and bent singlet isomers of HC 2 N.

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Section: A Equilibrium Structures Harmonic Frequencies and Equilibrsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Accurate ab initio quartic force fields of cyclic and bent HC2N isomers

Inostroza

Huang

Lee

2011

The Journal of Chemical Physics

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“…Strains were exponentially grown without (−URA) or with uracil (+URA), or with 200 mg/l of 6‐azauracil (+6AU). β‐galactosidase was expressed in arbitrary units (Miller, 1972), where 1.0 is the level measured in wild‐type cells grown in CSM. Broken arrows correspond to the transcriptional initiator regions, shown in black for full‐length URA2 mRNA and in grey for short upstream untranslated RNAs (Thiebaut et al , 2008).…”

Section: Resultsmentioning

confidence: 99%

Mutations of RNA polymerase II activate key genes of the nucleoside triphosphate biosynthetic pathways

Kwapisz

Wéry

Després

et al. 2008

EMBO J

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The yeast URA2 gene, encoding the rate-limiting enzyme of UTP biosynthesis, is transcriptionally activated by UTP shortage. In contrast to other genes of the UTP pathway, this activation is not governed by the Ppr1 activator. Moreover, it is not due to an increased recruitment of RNA polymerase II at the URA2 promoter, but to its much more effective progression beyond the URA2 mRNA start site(s). Regulatory mutants constitutively expressing URA2 resulted from cis-acting deletions upstream of the transcription initiator region, or from amino-acid replacements altering the RNA polymerase II Switch 1 loop domain, such as rpb1-L1397S. These two mutation classes allowed RNA polymerase to progress downstream of the URA2 mRNA start site(s). rpb1-L1397S had similar effects on IMD2 (IMP dehydrogenase) and URA8 (CTP synthase), and thus specifically activated the rate-limiting steps of UTP, GTP and CTP biosynthesis. These data suggest that the Switch 1 loop of RNA polymerase II, located at the downstream end of the transcription bubble, may operate as a specific sensor of the nucleoside triphosphates available for transcription.

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“…1 So far, many spectroscopic studies have been reported for the radical and its deuterated species using ESR, 1-3 pure rotational, 4-7 vibrational, [8][9][10][11][12][13][14][15][16] and electronic spectroscopy. [15][16][17][18] The main issue of the past studies was the geometric structure of the ground electronic state.…”

Section: Introductionmentioning

confidence: 99%

Electronic spectroscopy of the HCCN radical

Nakajima

Toyoshima

Sato

et al. 2013

The Journal of Chemical Physics

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The Ã(3)A"-X̃(3)Σ(-) electronic transition of the HCCN∕DCCN radical was observed by laser-induced fluorescence spectroscopy. Rotationally resolved excitation spectra were observed for HCCN and DCCN, and effective molecular constants of the upper state were determined. The observed intensities of the rotational lines were anomalous, probably due to a level-dependent non-radiative decay process in the excited state. Fluorescence depletion spectroscopy was applied in order to observe non-fluorescent vibronic levels. A dispersed fluorescence spectrum was also observed to determine the vibrational level structure in the ground electronic state. The observed vibrational structures in the fluorescence depletion and dispersed fluorescence spectra were tentatively assigned based on the results of ab initio calculations.

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Quasi-linearity in HCCN: effects of the v2 fundamental

Cited by 17 publications

References 20 publications

Accurate ab initio quartic force fields of cyclic and bent HC2N isomers

Accurate ab initio quartic force fields of cyclic and bent HC2N isomers

Mutations of RNA polymerase II activate key genes of the nucleoside triphosphate biosynthetic pathways

Electronic spectroscopy of the HCCN radical

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