The ionization potentials of ammonia and ammonia-d3. Measured by photoelectron spectroscopy, and an indo calculation of these values

Branton, G. R.; Frost, D. C.; Herring, F. G.; McDowell, C. A.; Stenhouse, I. A.

doi:10.1016/0009-2614(69)85115-8

Cited by 58 publications

(18 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The analyses of both the vibrational pattern [1] and of the rotational fine structure of some vibronic peaks [2] of the UV absorption band occurring at 217 nm have led to the conclusion that the excited electronic state has a planar equilibrium nuclear configuration, belonging to D 3h point group. A very similar vibrational pattern has also been observed in the lower-energy region of its photoelectron spectrum, leading to the conclusion that even thẽ X 2 A 00 2 ionic state is planar [3][4][5]. Both the splitting of the energy levels of the rovibrational spectrum and the well-resolved vibrational pattern of the electronic and photoelectronic spectra provide important experimental data for theoreticians involved in the application of sophisticated theoretical models for treating strong anharmonic effects [6,7], and in the development of efficient methodologies for the calculations of spectroscopic band shapes, that is, Franck-Condon (FC) factors.…”

Section: Introductionsupporting

confidence: 61%

“…A linearized internal coordinate s j coincides with the curvilinear one S j in the limit of infinitesimal displacements of atoms from their equilibrium positions. Therefore, in the range of validity of the harmonic approximation, there is no distinction between linear and curvilinear coordinates, but when large displacements are involved, such as those observed in going from the equilibrium geometry of NH 3 to that of NH 3 ? , the two sets of coordinates are no longer equivalent.…”

Section: Theoretical Approachmentioning

confidence: 97%

“…At the MP4/TZ level of approximation, the potential energy surface of NH 3 ? as a function of " Q 1 and " Q 2 ; the symmetric stretching and bending curvilinear normal coordinates, respectively, has been calculated over a grid of 431 points, covering the range r eq À 0:05Å r r eq þ Fig.…”

Section: Theoretical Approachmentioning

confidence: 99%

“…The observed vibrational spacing is ca. 0.12 eV (970 cm -1 ), so that the long vibrational progression has been assigned to the m 2 mode Table 1 Predicted -MP4/TZ and CC/QZ-bond lengths (r eq , Å ), valence angles \HNH (h eq , degrees) and harmonic frequencies of the two symmetric modes (m i as wavenumbers, cm -1 ) of NH 3 [39]), the so-called umbrella mode. In the high-resolution spectrum recorded by Edvardsson et al [38], the strong progression due to the symmetric bending mode is accompanied by a much weaker but well-resolved one, falling at higher energy, which was tentatively assigned to the asymmetric bending mode with one more quantum on the symmetric bending mode.…”

Section: Theoretical Approachmentioning

confidence: 99%

“…A high-order polynomial for describing the strong anharmonic couplings between the two modes was necessary for correcting the spurious displacement of the symmetric stretching mode predicted by Duschinsky's transformation in the Cartesian representation of the normal modes [10], which causes the appearance in the computed spectrum of vibrational progressions that are not present in the observed one. The adopted methodology is therefore quite cumbersome, requiring the knowledge of the potential energy of NH 3 ? on a large grid of nuclear coordinates.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Franck–Condon factors in curvilinear coordinates: the photoelectron spectrum of ammonia

et al. 2012

View full text Add to dashboard Cite

An approach to the calculation of FranckCondon factors in curvilinear coordinates is outlined. The approach is based on curvilinear normal coordinates, which allows for an easy extension of Duschinsky's transformation to the case of curvilinear coordinates, and on the power series expansion of the kinetic energy operator. Its usefulness in the case of molecules undergoing large displacements of their equilibrium nuclear configurations upon excitation is then demonstrated by an application to the vibrational structure of the photoelectron spectrum of ammonia, using an anharmonic potential only for the symmetric stretching and bending coordinates of the radical cation.

show abstract

Section: Introductionsupporting

confidence: 61%

Section: Theoretical Approachmentioning

confidence: 97%

Section: Theoretical Approachmentioning

confidence: 99%

Section: Theoretical Approachmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Franck–Condon factors in curvilinear coordinates: the photoelectron spectrum of ammonia

et al. 2012

View full text Add to dashboard Cite

show abstract

Über die Reihenfolge der obersten besetzten Molekülorbitale im Phosphorin‐System

1971

View full text Add to dashboard Cite

Sequence of Highest Occupied Molecular Orbitals in the Phosphorin System

Oehling

Schäfer

Schweig

1971

Angew. Chem. Int. Ed. Engl.

View full text Add to dashboard Cite

Residual triethylamine is removed by dissolution in ethyl acetate and extraction with cold 0.1 N HCl. The organic phase is evaporated down, 1 N NaOH (300ml) is added followed by enough methanol, THF, or dioxane to give a homogeneous solution. The mixture is stirred for the prescribed length of time, evaporated down to half its original volume in uacuu, and extracted three times with ethyl acetate [after prior acidification in the case of ( 5 ) !].If necessary the extract is decolorized with animal charcoal, dried over MgSO,, and the solvent is evaporated off. The resulting oils soon crystallize on standing. The aromatic phosphorins, which are analogs of pyridine, contain a trivalent phosphorus atom of coordination number 2 whose bonding has hitherto hardly been studied. A quantum-mechanical studyt3' has shown that the highest occupied molecular orbital (HOMO) is a A-MO, whereas the corresponding orbital in pyridine describes the lone pair (n-MO) on the nitrogen atom. The fundamental importance of the HOMO for properties and reactivity of a compound prompted us to seek experimental confirmation of the theoretical predictions by studying the photoelectron spectrum of 2,4,6-tri-tert-butylphosphorin (I). The band maxima in the spectrum of ( I ) lie at 8.98.6, and 10.0 eV, those in the spectrum of (2) at 8.6 and 9.3 eV. As expected, the phosphorins are more readily ionized than corresponding pyridines. The band maxima in unsubstituted pyridine are found at 9.6,9.7, and 10.5 eVC6]. Hence the three tert-butyl groups in (2) lower the ionization potential (ZP) by 1.0 to 1.2 eV.The size of molecules (1) and (2) precludes direct CNDO/2 calculations[71; instead calculations were performed on 2,4,6-trimethylphosphorin (3) and 2,4,6-trimethylpyridine (4). A series of model calculations on the mono-, di-, and tri-methyl and the mono-and di-tert-butyl substituted compounds showed that replacement of a methyl by a tert-butyl group shifts the orbital energy by an additive component but that the orbital sequence is retained. For compound (4) it is n, A, A, o and for (3) A, n, Q, K (see Fig. 2).These results strongly suggest that the first photoelectron band of (2) arises from overlap of an n-and a A ionization, and the second band from a K ionization. The intensity ratio of the first to the second band (2 : 1) may be regarded as supporting evidence. The same orbital sequence has recently also been suggested for pyridine itself by photoelectron spectroscopy [']. Figure 2 the first and third band ofphosphorin (1) should be assigned to a A ionization, while the second band should result from an n-and a o ionization. Experience shows, however, that semiempirical valenceelectron calculations on unsaturated systems afford (3 orbitals of too high energy"], thus making assignment of A, n, A, and Q ionization to the three photoelectron bands more likely. According toIt is to be expected from Figure 2 that the ZP of the lone pairs of ( I ) and (2) are almost equal. The ZP of the lone pairs of NH, and PH, also differ by only 0.25 eVtlol. On...

show abstract

The ionization potentials of ammonia and ammonia-d3. Measured by photoelectron spectroscopy, and an indo calculation of these values

Cited by 58 publications

References 13 publications

Franck–Condon factors in curvilinear coordinates: the photoelectron spectrum of ammonia

Franck–Condon factors in curvilinear coordinates: the photoelectron spectrum of ammonia

Über die Reihenfolge der obersten besetzten Molekülorbitale im Phosphorin‐System

Sequence of Highest Occupied Molecular Orbitals in the Phosphorin System

Contact Info

Product

Resources

About