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Lemmens AK, Rap DB, Brünken S, Buma WJ, Rijs AM. Polycyclic aromatic hydrocarbon growth in a benzene discharge explored by IR-UV action spectroscopy. Phys Chem Chem Phys 2022; 24:14816-14824. [PMID: 35695165 PMCID: PMC9215700 DOI: 10.1039/d2cp01631a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Infrared signatures of polycyclic aromatic hydrocarbons (PAHs) are detected towards many phases of stellar evolution. PAHs are major players in the carbon chemistry of the interstellar medium, forming the connection between small hydrocarbons and large fullerenes. However, as details on the formation of PAHs in these environments are still unclear, modeling their abundance and chemistry has remained far from trivial. By combining molecular beam mass-selective IR spectroscopy and calculated IR spectra, we analyze the discharge of benzene and identify resulting products including larger PAHs, radicals and intermediates that serve as promising candidates for radio astronomical searches. The identification of various reaction products indicates that different gas-phase reaction mechanisms leading to PAH growth must occur under the same conditions to account for all observed PAH-related species, thereby revealing the complex and interconnected network of PAH formation pathways. The results of this study highlight key (exothermic) reactions that need to be included in astrochemical models describing the carbon chemistry in our universe.
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Affiliation(s)
- Alexander K. Lemmens
- Van't Hoff Institute for Molecular Sciences, University of AmsterdamScience Park 9041098 XHAmsterdamThe Netherlands,Institute for Molecules and Materials, FELIX Laboratory, Radboud UniversityToernooiveld 76525 EDNijmegenThe Netherlands
| | - Daniël B. Rap
- Institute for Molecules and Materials, FELIX Laboratory, Radboud UniversityToernooiveld 76525 EDNijmegenThe Netherlands
| | - Sandra Brünken
- Institute for Molecules and Materials, FELIX Laboratory, Radboud UniversityToernooiveld 76525 EDNijmegenThe Netherlands
| | - Wybren Jan Buma
- Van't Hoff Institute for Molecular Sciences, University of AmsterdamScience Park 9041098 XHAmsterdamThe Netherlands,Institute for Molecules and Materials, FELIX Laboratory, Radboud UniversityToernooiveld 76525 EDNijmegenThe Netherlands
| | - Anouk M. Rijs
- Division of BioAnalytical Chemistry, AIMMS Amsterdam Institute of Molecular and Life Sciences, Vrije Universiteit AmsterdamDe Boelelaan 11081081 HV AmsterdamThe Netherlands
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2
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Levey ZD, Laws BA, Sundar SP, Nauta K, Kable SH, da Silva G, Stanton JF, Schmidt TW. PAH Growth in Flames and Space: Formation of the Phenalenyl Radical. J Phys Chem A 2021; 126:101-108. [PMID: 34936357 DOI: 10.1021/acs.jpca.1c08310] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are intermediates in the formation of soot particles and interstellar grains. However, their formation mechanisms in combustion and interstellar environments are not fully understood. The production of tricyclic PAHs and, in particular, the conversion of a PAH containing a five-membered ring to one with a six-membered ring are of interest to explain PAH abundances in combustion processes. In the present work, resonant ionization mass spectrometry in conjunction with isotopic labeling is used to investigate the formation of the phenalenyl radical from acenaphthylene and methane in an electrical discharge. We show that in this environment the CH cycloaddition mechanism converts a five-membered ring to a six-membered ring. This mechanism can occur in tandem with other PAH formation mechanisms such as hydrogen abstraction/acetylene addition (HACA) to produce larger PAHs in flames and the interstellar medium.
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Affiliation(s)
- Zachariah D Levey
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Benjamin A Laws
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Srivathsan P Sundar
- Department of Chemical Engineering, The University of Melbourne, Parkville 3010, Australia
| | - Klaas Nauta
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Scott H Kable
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
| | - Gabriel da Silva
- Department of Chemical Engineering, The University of Melbourne, Parkville 3010, Australia
| | - John F Stanton
- Department of Chemistry, University of Florida, Gainesville, Florida 32611, United States
| | - Timothy W Schmidt
- Centre of Excellence in Exciton Science, University of New South Wales, Sydney, NSW 2052, Australia
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3
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Dobulis MA, Thompson MC, Jarrold CC. Identification of Isoprene Oxidation Reaction Products via Anion Photoelectron Spectroscopy. J Phys Chem A 2021; 125:10089-10102. [PMID: 34755517 DOI: 10.1021/acs.jpca.1c08176] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We present a study on the oxidation of isoprene under several different conditions that may model both atmospheric and combustion chemistry. Anions, formed by passing isoprene/oxidant gas mixtures through a pulsed discharge generating a range of species, are separated via mass spectrometry and characterized by anion photoelectron (PE) spectroscopy supported by computations. Specifically, a UV-irradiated isoprene/O2 mixture, which additionally produces O3, and an isoprene/O2/H2 mixture, which generates •OH when passed through the discharge, were sampled. The mass spectra of ions generated under both conditions show the production of intact molecular ions, ion-molecule complexes (e.g., O2-, O4-, and O2-·isoprene), and singly deprotonated species (e.g., deprotonated isoprene, C5H7-). In addition, both smaller and oxidized fragments are observed using both gas mixtures, though relative abundances differ. From the UV-irradiated isoprene/O2 gas mixture, additional intact molecular products of reactions initiated by ozonolysis of isoprene, methylglyoxal, and dimethylglyoxal were observed. Fragmentation and oxidation of isoprene observed in both gas mixtures included species with m/z 39, 53, 67, 69, and 83 that we attribute to a series of alkyl- and alkenoxide-based anions. The coexistence of intact molecules and complexes with fragments and reaction products demonstrates the versatility of this ion source as a simple and efficient anion formation method for studying species that may be relevant in atmospheric and combustion chemistry.
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Affiliation(s)
- Marissa A Dobulis
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Michael C Thompson
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
| | - Caroline Chick Jarrold
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, United States
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Ross SD, Flores J, Khani S, Hewett DM, Reilly NJ. Optical Identification of the Resonance-Stabilized para-Ethynylbenzyl Radical. J Phys Chem A 2021; 125:9115-9127. [PMID: 34614356 DOI: 10.1021/acs.jpca.1c07039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the spectroscopic observation of the jet-cooled para-ethynylbenzyl (PEB) radical, a resonance-stabilized isomer of C9H7. The radical was produced in a discharge of p-ethynyltoluene diluted in argon and probed by resonant two-color two-photon ionization (R2C2PI) spectroscopy. The origin of the D0(2B1)-D1(2B1) transition of PEB appears at 19,506 cm-1. A resonant two-color ion-yield scan reveals an adiabatic ionization energy (AIE) of 7.177(1) eV, which is almost symmetrically bracketed by CBS-QB3 and B3LYP/6-311G++(d,p) calculations. The electronic spectrum exhibits pervasive Fermi resonances, in that most a1 fundamentals are accompanied by similarly intense overtones or combination bands of non-totally symmetric modes that would carry little intensity in the harmonic approximation. Under the same experimental conditions, the m/z = 115 R2C2PI spectrum of the p-ethynyltoluene discharge also exhibits contributions from the m-ethynylbenzyl and 1-phenylpropargyl radicals. The former, like PEB, is observed herein for the first time, and its identity is confirmed by measurement and calculation of its AIE and D0-D1 origin transition energy; the latter is identified by comparison with its known electronic spectrum (J. Am. Chem. Soc., 2008, 130, 3137-3142). Both species are found to co-exist with PEB at levels vastly greater than might be explained by any precursor sample impurity, implying that interconversion of ethynylbenzyl motifs is feasible in energetic environments such as plasmas and flames, wherein resonance-stabilized radicals are persistent.
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Affiliation(s)
- Sederra D Ross
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Jonathan Flores
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Sima Khani
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Daniel M Hewett
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Neil J Reilly
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
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Ross SD, Flores J, Hewett DM, Reilly NJ. Electronic Spectroscopy of cis- and trans- meta-Vinylbenzyl Radicals. J Phys Chem A 2021; 125:6420-6436. [PMID: 34260230 DOI: 10.1021/acs.jpca.1c04496] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The D0(2A″)-D1(2A″) electronic transition of resonance-stabilized radical C9H9 isomers cis- and trans-meta-vinylbenzyl (MVB) has been investigated using resonant two-color two-photon ionization (R2C2PI) and laser-induced fluorescence. The radicals were produced in a discharge of m-vinyltoluene diluted in Ar and probed under jet-cooled conditions. The origin bands of the cis and trans conformers are at 19 037 and 18 939 cm-1, respectively. Adiabatic ionization energies near 7.17 eV were determined for both conformers from two-color ion-yield scans. Dispersed fluorescence (DF) was used to conclusively identify the cis-conformer: ground-state cis-MVB eigenvalues calculated for a Fourier series fit of a computed vinyl torsion potential are in excellent agreement with torsional transitions in the 19 037 cm-1 DF spectrum. R2C2PI features arising from cis- or trans-MVB were distinguished by optical-optical hole-burning spectroscopy and vibronic assignments were made with guidance from density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. There is a notable absence of mirror symmetry between excitation and emission spectra for several totally symmetric modes, whereby modes that are conspicuous in emission are nearly absent in excitation, and vice versa. This effect is largely ascribed to interference between Franck-Condon and Herzberg-Teller contributions to the electronic transition moment, and its pervasiveness a consequence of the low symmetry (Cs) of the molecule, which permits intensity borrowing from several relatively bright electronic states of A″ symmetry.
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Affiliation(s)
- Sederra D Ross
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Jonathan Flores
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Daniel M Hewett
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
| | - Neil J Reilly
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston, Massachusetts 02125, United States
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Yuan W, Zhao L, Yang J, Zhou Z, Li Y, Qi F. Insights into the Decomposition and Oxidation Chemistry of p-Xylene in Laminar Premixed Flames. J Phys Chem A 2021; 125:3189-3197. [PMID: 33829792 DOI: 10.1021/acs.jpca.1c00745] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This work reports an experimental and kinetic modeling investigation on laminar premixed flame of p-xylene at 0.04 atm and equivalence ratios of 0.75, 1.0, and 1.79. Intermediates such as the p-xylyl radical, p-xylylene, and styrene, as well as polycyclic aromatic hydrocarbons (PAHs), were detected by using synchrotron vacuum ultraviolet photoionization mass spectrometry. Based on our previous aromatic kinetic model, a detailed kinetic model of p-xylene combustion was developed, and the model was validated against the present flame structure data. Model analysis work was also performed in order to reveal the important reactions in p-xylene decomposition and oxidation. The H-abstraction reactions leading to the p-xylyl radical are found to control the consumption of p-xylene in all the three flames. In the rich flame, p-xylyl mainly suffers the H-elimination and isomerization reactions, which produce p-xylylene and the o-xylyl radical, respectively. The further decomposition reactions of the o-xylyl radical contribute to the production of styrene, which is another important C8 intermediate observed in the rich flame. In the stoichiometric and lean flames, p-xylyl mainly suffers the oxidation reactions by O, which give p-methylbenzaldehyde as major product. The growth pathways of PAHs in the rich flame were also investigated in this work. Indenyl, indene, naphthalene, and phenanthrene were observed as the abundantly produced bicyclic and tricyclic PAHs due to the existence of direct formation pathways from the decomposition of p-xylyl radical.
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Affiliation(s)
- Wenhao Yuan
- Key Laboratory for Power Machinery and Engineering of MOE, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Long Zhao
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
| | - Jiuzhong Yang
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, P. R. China
| | - Zhongyue Zhou
- Key Laboratory for Power Machinery and Engineering of MOE, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Yuyang Li
- Key Laboratory for Power Machinery and Engineering of MOE, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
| | - Fei Qi
- Key Laboratory for Power Machinery and Engineering of MOE, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, P. R. China
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Hirsch F, Pachner K, Fischer I, Issler K, Petersen J, Mitric R, Bakels S, Rijs AM. Do Xylylenes Isomerize in Pyrolysis? Chemphyschem 2020; 21:1515-1518. [PMID: 32501625 PMCID: PMC7496364 DOI: 10.1002/cphc.202000317] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 06/05/2020] [Indexed: 01/06/2023]
Abstract
We report infrared spectra of xylylene isomers in the gas phase, using free electron laser (FEL) radiation. All xylylenes were generated by flash pyrolysis. The IR spectra were obtained by monitoring the ion dip signal, using a IR/UV double resonance scheme. A gas phase IR spectrum of para-xylylene was recorded, whereas ortho- and meta-xylylene were found to partially rearrange to benzocyclobutene and styrene. Computations of the UV oscillator strength for all molecules were carried out and provde an explanation for the observation of the isomerization products.
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Affiliation(s)
- Florian Hirsch
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Kai Pachner
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Ingo Fischer
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Kevin Issler
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Jens Petersen
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Roland Mitric
- Institute for Physical and Theoretical Chemistry, University of Würzburg, Am Hubland, 97074, Würzburg, Germany
| | - Sjors Bakels
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, The, Netherlands
| | - Anouk M Rijs
- Radboud University, Institute for Molecules and Materials, FELIX Laboratory, Toernooiveld 7, 6525 ED, Nijmegen, The, Netherlands
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Reilly NJ, Kokkin DL, Ward ML, Flores J, Ross SD, McCaslin LM, Stanton JF. Gas-Phase Optical Detection of 3-Ethynylcyclopentenyl: A Resonance-Stabilized C7H7 Radical with an Embedded 1-Vinylpropargyl Chromophore. J Am Chem Soc 2020; 142:10400-10411. [DOI: 10.1021/jacs.0c01579] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Neil J. Reilly
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston Massachusetts 02125, United States
| | - Damian L. Kokkin
- Department of Chemistry, Marquette University, P.O. Box 1881 Milwaukee, Wisconsin 53201, United States
| | - Meredith L. Ward
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston Massachusetts 02125, United States
| | - Jonathan Flores
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston Massachusetts 02125, United States
| | - Sederra D. Ross
- Department of Chemistry, University of Massachusetts Boston, 100 Morrissey Boulevard, Boston Massachusetts 02125, United States
| | - Laura M. McCaslin
- Institute of Chemistry and the Fritz Haber Center for Molecular Dynamics, The Hebrew University, Jerusalem 9190401, Israel
| | - John F. Stanton
- Quantum Theory Project, Departments of Chemistry and Physics, The University of Florida, Gainesville Florida 32611, United States
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Hirsch F, Flock M, Fischer I, Bakels S, Rijs AM. The Gas-Phase Infrared Spectra of Xylyl Radicals. J Phys Chem A 2019; 123:9573-9578. [PMID: 31593463 DOI: 10.1021/acs.jpca.9b09153] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The three isomers of the xylyl radical, C8H9, are possible intermediates in the formation of soot and polycyclic aromatic hydrocarbons (PAH). Their infrared spectra have been recorded by IR/UV ion dip spectroscopy using free electron laser radiation. The radicals were generated by flash pyrolysis from the corresponding nitrites and resonantly ionized via the D3 ← D0 transition around 310 nm. Mid-infrared spectra of the three xylyl isomers were recorded between 550 and 1700 cm-1 and are in excellent agreement with computations, provided that overtones and combination bands are included in the simulation. The results show that the three xylyl isomers can be distinguished by their infrared spectra and that no isomerization occurs in the pyrolysis reactor. The IR spectra obtained at m/z = 208 indicate that dimerization of xylyl radicals leads to substituted stilbenes, which has not been observed for benzyl.
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Affiliation(s)
- Florian Hirsch
- Institute of Physical and Theoretical Chemistry , University of Wuerzburg , Am Hubland Süd, 97074 Würzburg , Germany
| | - Marco Flock
- Institute of Physical and Theoretical Chemistry , University of Wuerzburg , Am Hubland Süd, 97074 Würzburg , Germany
| | - Ingo Fischer
- Institute of Physical and Theoretical Chemistry , University of Wuerzburg , Am Hubland Süd, 97074 Würzburg , Germany
| | - Sjors Bakels
- Radboud University , Institute for Molecules and Materials, FELIX Laboratory , Toernooiveld 7-c , 6525 Nijmegen , the Netherlands
| | - Anouk M Rijs
- Radboud University , Institute for Molecules and Materials, FELIX Laboratory , Toernooiveld 7-c , 6525 Nijmegen , the Netherlands
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Steglich M, Bodi A, Maier JP, Hemberger P. Probing different spin states in xylyl radicals and ions. Phys Chem Chem Phys 2018; 20:7180-7189. [PMID: 29480313 DOI: 10.1039/c7cp08466h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Resonant one-color two-photon ionization spectroscopy and mass-selected threshold photoelectron spectroscopy were applied to study the electronic doublet states of the three xylyl (methyl-benzyl) radicals above 3.9 eV as well as the singlet and triplet states of the cations up to 10.5 eV. The experiments are complemented by quantum chemical calculations and Franck-Condon simulations to characterize the transitions and to identify the origin bands, allowing a precise determination of singlet-triplet splittings in the cations. Torsional motions of the methyl group notably affect the D0 → D3 transition of m-xylyl. All other investigated transitions either lead to electronic states with very low rotational barriers or suffer from spectral broadening in excess of methyl torsional energy levels. The methyl internal rotational potential is faithfully reproduced with the most basic ab initio methods, yet hyperconjugation could not be identified as a significant force shaping them. Time-dependent density functional theory describes the excited electronic states better than wave function theory approaches, notably EOM-CCSD.
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