Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH3–CC–CH+3and CD3–CC–CD+3

Jacovella, Ugo; Gans, Bérenger; Merkt, Frédéric

doi:10.1080/00268976.2015.1005708

Cited by 5 publications

(9 citation statements)

References 38 publications

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“…The bound-state structure in these spectra has been discussed previously, and here we focus on the structure of the ionization continua. The ionization energies of 1- and 2-butyne are 10.178 ± 0.005 eV and 9.5611 ± 0.0006 eV, respectively. − As was discussed previously, the absorption cross section for 1-butyne is in good agreement with earlier measurements . The cross section above 10.6 eV remains flat up to at least 11.8 eV, the limit of the earlier data .…”

Section: Resultssupporting

confidence: 86%

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A Near-Threshold Shape Resonance in the Valence-Shell Photoabsorption of Linear Alkynes

et al. 2015

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The room-temperature photoabsorption spectra of a number of linear alkynes with internal triple bonds (e.g., 2-butyne, 2-pentyne, and 2- and 3-hexyne) show similar resonances just above the lowest ionization threshold of the neutral molecules. These features result in a substantial enhancement of the photoabsorption cross sections relative to the cross sections of alkynes with terminal triple bonds (e.g., propyne, 1-butyne, 1-pentyne, ...). Based on earlier work on 2-butyne [ Xu et al., J. Chem. Phys. 2012, 136, 154303 ], these features are assigned to excitation from the neutral highest occupied molecular orbital (HOMO) to a shape resonance with g (l = 4) character and approximate π symmetry. This generic behavior results from the similarity of the HOMOs in all internal alkynes, as well as the similarity of the corresponding gπ virtual orbital in the continuum. Theoretical calculations of the absorption spectrum above the ionization threshold for the 2- and 3-alkynes show the presence of a shape resonance when the coupling between the two degenerate or nearly degenerate π channels is included, with a dominant contribution from l = 4. These calculations thus confirm the qualitative arguments for the importance of the l = 4 continuum near threshold for internal alkynes, which should also apply to other linear internal alkynes and alkynyl radicals. The 1-alkynes do not have such high partial waves present in the shape resonance. The lower l partial waves in these systems are consistent with the broader features observed in the corresponding spectra.

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Section: Resultssupporting

confidence: 86%

“…The ionization energies of 1-and 2butyne are 10.178 ± 0.005 eV and 9.5611 ± 0.0006 eV, respectively. [20][21][22] As was discussed previously, the absorption cross section for 1-butyne is in good agreement with earlier measurements. 23 The cross section above 10.6 eV remains flat up to at least 11.8 eV, the limit of the earlier data.…”

Section: Methodssupporting

confidence: 91%

A Near-Threshold Shape Resonance in the Valence-Shell Photoabsorption of Linear Alkynes

et al. 2015

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“…In CH 3 C 3 N + , we can suspect a spin-orbit splitting of the same order of magnitude, slightly decreased by the off-axis H atoms [43,44]. Thus, higher-resolved spectra of theX þ2 E X1 A 1 transition should exhibit a complex rovibronic structure due to the combination of the Jahn-Teller effect and spin-orbit coupling like in propyne [34,36] and the 2-butyne [45] cations. Pulsedfield-ionization zero-kinetic-energy photoelectron spectroscopy would be perfectly suited for this purpose.…”

Section: Resultsmentioning

confidence: 97%

Photoionization spectroscopy of CH3C3N in the vacuum-ultraviolet range

Lamarre

Falvo

Alcaraz

et al. 2015

Journal of Molecular Spectroscopy

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International audienceUsing vacuum-ultraviolet (VUV) synchrotron radiation, threshold and dissociative photoionization of cyanopropyne (CH3C3N) in the gas phase have been studied from 86 000 cm−1 up to 180 000 cm−1 by recording Threshold-PhotoElectron Spectrum (TPES) and PhotoIon Yield (PIY). Ionization energies of the four lowest electronic states X̃+2E,Ã+2A1,B̃+2E and C̃+ of CH3C3N+ are derived from the TPES with a better accuracy than previously reported. The adiabatic ionization potential of CH3C3N is measured as 86872±20 cm−1. A description of the vibrational structure of these states is proposed leading to the first determination of the vibrational frequencies for most modes. The vibrational assignments of the X̃+ state are supported by density functional theory calculations. In addition, dissociative photoionization spectra have been recorded for several cationic fragments in the range 12–15.5 eV (96 790–125 000 cm−1) and they bring new information on the photophysics of CH3C3N+. Threshold energies for the cationic dissociative channels leading to CH2C3N+, CHC3N+, HC3H+, HCNH+ and CH3+ have been measured for the first time and are compared with quantum chemical calculations

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“…+ is expected to be an active mode of the linear Jahn-Teller effect and is more likely to be observed than the ν 16a,b + mode. 36 The adiabatic ionization energy of 2-butyne has recently been determined to be 77 115.1 ± 2.0 cm −1 . 36 The ground state cation also has a small spin-orbit splitting that is not resolved in the present spectra; because this splitting is small, we use the center of gravity of the spin orbit states (77 120 cm −1 ) in the calculation of the n * values given in Table II.…”

Section: B 2-butynementioning

confidence: 99%

“…However, because the same pattern of two bands is observed in the same location relative to the 3d y 2, v 2 ′ = 0, 1, and 2 states, we have reassigned these bands to the v 2 ′ = 0-2, v 11b ′ = 1, and v 2 ′ = 0-2, v 4 ′ = 1 bands. The ν 11b vibration corresponds to the b 1 component of the CH 3 rock, while the ν 4 vibration The effective principal quantum numbers were calculated by using Equation ( 1), the 2-butyne ionization energy 36 to the center of gravity of the two spin-orbit states of the ion (77 120 cm −1 ), and the Rydberg constant for 2-butyne (109 736.2 cm −1 ).…”

Section: B 2-butynementioning

confidence: 99%

High-resolution vacuum-ultraviolet photoabsorption spectra of 1-butyne and 2-butyne

Jacovella

Holland

Boyé-Péronne

et al. 2015

The Journal of Chemical Physics

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The absolute photoabsorption cross sections of 1- and 2-butyne have been recorded at high resolution by using the vacuum-ultraviolet Fourier-Transform spectrometer at the SOLEIL Synchrotron. Both spectra show more resolved structure than previously observed, especially in the case of 2-butyne. In this work, we assess the potential importance of Rydberg states with higher values of orbital angular momentum, l, than are typically observed in photoabsorption experiments from ground state molecules. We show how the character of the highest occupied molecular orbitals in 1- and 2-butyne suggests the potential importance of transitions to such high-l (l = 3 and 4) Rydberg states. Furthermore, we use theoretical calculations of the partial wave composition of the absorption cross section just above the ionization threshold and the principle of continuity of oscillator strength through an ionization threshold to support this conclusion. The new absolute photoabsorption cross sections are discussed in light of these arguments, and the results are consistent with the expectations. This type of argument should be valuable for assessing the potential importance of different Rydberg series when sufficiently accurate direct quantum chemical calculations are difficult, for example, in the n ≥ 5 manifolds of excited states of larger molecules.

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Internal rotation, spin–orbit coupling, and low-frequency vibrations in the ground state of CH₃–CC–CH⁺₃and CD₃–CC–CD⁺₃

Cited by 5 publications

References 38 publications

A Near-Threshold Shape Resonance in the Valence-Shell Photoabsorption of Linear Alkynes

A Near-Threshold Shape Resonance in the Valence-Shell Photoabsorption of Linear Alkynes

Photoionization spectroscopy of CH3C3N in the vacuum-ultraviolet range

High-resolution vacuum-ultraviolet photoabsorption spectra of 1-butyne and 2-butyne

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