The two-dimensional anharmonic oscillator

Duckett, J. A.; Robiette, A. G.; Mills, Ian

doi:10.1016/0022-2852(76)90260-5

Cited by 66 publications

(10 citation statements)

References 13 publications

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“…The bending potential is best considered in relation to the linear SiNCO skeleton as datum. This is widely used for fitting the PE surfaces of quasi-linear molecules, where the potential is a mixture of quadratic and quartic terms in the variable (p-SiCN, radians) [9,[30][31][32]. A study of the equilibrium geometry, with fixed internal rotation angles (HSiNC), shows a double minimum, with trans-HSiNC slightly lower (by 0.063 cm À1 ) in total energy than cis-HSiNC.…”

Section: The Potential Energy Surfaces (Pes)mentioning

confidence: 99%

“…3, that the bending potential is significantly different from a quadratic function; several fits were attempted for the available B3LYP derived SiNC angle bending data. These varied from qua- dratic + quartic [31,32], quadratic + Lorentzian [11,9,30], including some higher terms. In the following Equations, x is 180°-SiNC (x, radians), with energy (E, cm À1 ), while standard deviations (SD) are given numerically in relation to the last digit shown: Most fits for quasi-linear isocyanates and related compounds use terms of types (b) and (d); comparison of (b) and (c), shows that the fit is rapidly convergent with powers of x 2 .…”

Section: The Potential Energy Surfaces (Pes)mentioning

confidence: 99%

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The molecular structure of difluoroisocyanato silane: A combined microwave spectral and theoretical study

Guirgis

Wang

Lirjoni

et al. 2010

Journal of Molecular Structure

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Section: The Potential Energy Surfaces (Pes)mentioning

confidence: 99%

Section: The Potential Energy Surfaces (Pes)mentioning

confidence: 99%

The molecular structure of difluoroisocyanato silane: A combined microwave spectral and theoretical study

Guirgis

Wang

Lirjoni

et al. 2010

Journal of Molecular Structure

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“…Although methyl isocyanate has only 7 atoms, it is theoretically challenging as it displays two large amplitude motions consistent with its quasi-symmetry. [2][3][4][5][6][7][8][9][10][11] The coupling between these two large amplitude motions must be treated exactly to properly model its energy level dia- Figure 11. TPES calculated with the vibration-bendingtorsion approach plotted in a) as a function of the photon energy.…”

Section: Discussionmentioning

confidence: 99%

“…Such species, of the WH 3 XYZ type, display two large amplitude motions, the WH 3 torsion and ∠WXY bending mode, leading to a singularity at the symmetrical C 3v configuration. Dedicated theoretical treatments developed to evaluate the rotation-bending-torsion energy levels of such species [2][3][4][5][6][7][8][9][10][11] were applied to the analysis of the microwave spectrum of methyl isothiocyanate 3,12 (CH 3 NCS), silyl isocyanate 5,7 (SiH 3 NCO), and methyl isocyanate. 8,[12][13][14] For the latter species, nearly 400 transitions could be assigned leading to its detection in the interstellar space medium.…”

Section: Introductionmentioning

confidence: 99%

“…In the first treatment, only the two large amplitude motions are considered. 2,3,5,[7][8][9][10][11] In the second one, making use of the harmonic adiabatic approximation, 23,24 the previous treatment is extended to include small amplitude vibrational modes. In agreement with Eland, 25 only the five small amplitude vibrational modes involving the NCO group are included because this group undergoes the largest structural changes upon ionization.…”

Section: Introductionmentioning

confidence: 99%

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Quasi-symmetry effects in the threshold photoelectron spectrum of methyl isocyanate

Harper

Coudert

Loison

et al. 2020

The Journal of Chemical Physics

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The vacuum-ultraviolet threshold photoelectron spectrum of methyl isocyanate CH 3 NCO has been recorded from 10.4 to 12 eV using synchrotron radiation and a coincidence technique allowing for a mass-discrimination of the photoelectron signal. A significant improvement is achieved over previous investigations as this experimental setup leads to a much more resolved spectrum. Ten sharp peaks and a broad feature spanning 1.2 eV were recorded. This spectrum consists of thẽ X + 2 A ←X 1 A andÃ + 2 A ←X 1 A ionizing transitions. For the former, the adiabatic ionization energy was determined experimentally to be 10.596(6) eV; for the latter its value was estimated to be 10.759(50) eV. Seven sharp peaks could be assigned to vibrational modes of the cationX + 2 A and neutralX 1 A ground electronic states involving only the NCO group atoms. Theoretical modeling of the threshold photoelectron spectrum has proven difficult as methyl isocyanate is a non-rigid molecule displaying large amplitude internal rotation of the methyl group and ∠CNC bending mode, leading to the quasi-symmetry. With the help of ab initio calculations, a theoretical model in which these two large amplitude motions are included in addition to the five small amplitude vibrational modes involving NCO group atoms is proposed. Comparison with the experimental spectrum shows that the broad feature and the strongest peaks line positions are well accounted for; their intensities are also fairly well reproduced after adjusting a few parameters.

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An Electron Diffraction Determination of the Molecular Structure of Hexamethylcarbodiphosphorane in the Gas Phase

et al. 1977

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The molecular structure of hexamethylcarbodiphosphorane, (CH,),P = C = P(CH3),, in the gas phase has been determined by electron diffraction. Principle bond lengths (ra) are: P-C. 181.4(3)prn, P=C, 159.4(3) pm; C-H, 108.9(4) pm. The angles between the P-C (methyl) bonds are 101.4(3)", and the apparent P = C = P angle is 147.6(5)". The single structure that fits the experimental data closest has C2 overall symmetry, but an even closer fit is obtained if free rotation about the P = C bonds is assumed. This and other evidence indicates that the molecule is probably a symmetric top, and that the P = C = P unit is linear in the average structure, with shrinkage caused by a low frequency bending vibration giving rise to the apparent non-linearity. Bestimmung der Molekiilstruktur von Hexamethylcarbodiphosphoran in der Gasphase durch ElektronenbeugungDie Molekiilstruktur von Hexamethylcarbodiphosphoran, (CH3)3P=C= P(CH,),, wurde in der Gasphase durch Elektronenbeugung bestimmt. Die hauptsachlichen Bindungslangen (ra) sind P-C = 181.4(3)pm, P = C = 159.4(3)pm, C-H = 108.9(4)pm. Die Winkel zwischen den P-C-(Methyl)-Bindungen betragen 101.4(3)", der scheinbare P = C = P-Winkel 147.6(5)". Die einzige fixierte Struktur, die die beste Anpassung an die MeDdaten ergibt, hat die Gesamtsymmetrie C1, doch wird fur ein Model1 mit freier Drehbarkeit um die P = C-Achse eine noch bessere f h r e i nstimmung gefunden. Daraus und aus anderen Hinweisen kann geschlossen werden, da13 das Molekul einen symmetrischen Kreisel bildet und daB die P= C = P-Einheit in der gemittelten Struktur linear ist. Die beobachtete Schrumpfung geht danach auf eine sehr niedrige Beugungsfrequenz zuriick, die zur scheinbaren Nichtlinearitat fuhrt.

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The two-dimensional anharmonic oscillator

Cited by 66 publications

References 13 publications

The molecular structure of difluoroisocyanato silane: A combined microwave spectral and theoretical study

The molecular structure of difluoroisocyanato silane: A combined microwave spectral and theoretical study

Quasi-symmetry effects in the threshold photoelectron spectrum of methyl isocyanate

An Electron Diffraction Determination of the Molecular Structure of Hexamethylcarbodiphosphorane in the Gas Phase

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