Investigation of the ν8and ν21bands of propane CH3CH2CH3at 11.5 and 10.9 µm: evidence of large amplitude tunnelling effects

Perrin, A.; Flaud, J.‐M.; Kwabia-Tchana, F.; Manceron, L.; Groner, P.

doi:10.1080/00268976.2018.1512720

Cited by 5 publications

(4 citation statements)

References 43 publications

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“…This will provide the position part of a linelist but, while the model presented here gives good relative intensities, absolute intensities will require a good model for the torsional vibrations to allow a complete partition function calculation. This has been discussed by Perrin et al [9] for normal propane.…”

Section: Discussionmentioning

confidence: 75%

“…The bands we have analyzed here are not affected by the torsional motions; the torsional splittings are probably comparable to the ground state torsional splittings of only a few MHz [54], so would require much higher resolution to be visible. However the ν8 and ν21 bands in normal propane show strong interactions with torsional motions and the analysis of these bands in normal propane required a model including states with two quanta in the torsional modes [9], and these bands are also visible in our spectra, and an analysis of these bands is likely to be the most informative about the torsion modes.…”

Section: Discussionmentioning

confidence: 94%

“…The Titan observation prompted a FT-IR study [2] at the Kitt Peak National Observatory (KPNO), though as improved spacecraft and ground-based astronomical observations were made [3,4] in the following years it became clear that laboratory data of better resolution as well as a more detailed analysis was required. This prompted several studies of propane [5][6][7], and recent articles by Perrin et al [8,9] summarize the several high-resolution studies that have been done that support investigation of Titan and NASA missions (Voyager, Galileo & Cassini) to the outer Solar System. The infra-red work has also been used to study propane that has also been found on Jupiter and Saturn [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

“…This implies significant intensity for hot bands involving these modes, given that the 2ν9−ν9 hot band has been analyzed as mentioned above. Fortunately from the analysis point of view the ground state, ν9, 2ν9 and ν26 do not show any torsional splittings, though other states do, significantly complicating their analysis [8,9].…”

Section: Introductionmentioning

confidence: 99%

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First high-resolution infrared spectra of 2–13C-propane: Analyses of the ν26 (B2) c-type and ν9 (A1) b-type bands

Daunt

Grzywacz

Western

et al. 2020

Journal of Molecular Structure

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This paper presents the first high resolution (Δν = 0.00096 cm −1) IR investigation of 2-13 C-propane. Spectra of the ν9(A1) CCC skeletal bending mode near 336.767 cm −1 (a b-type band) and the ν26(B2) methylene (CH2) rocking mode near 746.614 cm −1 (a c-type band) were recorded at the Canadian Light Source (CLS) synchrotron. The spectra were assigned both traditionally and with the aid of the PGOPHER program. As only limited microwave data are available for this molecule the present data was used to determine a new set of ground state constants that included centrifugal distortion terms. Upper state constants for both bands have been determined that provide a good simulation of the spectra. The analysis also included the strong a-type Coriolis resonance between the ν26 and 2ν9 states that causes strong perturbation-allowed transitions to appear in the spectrum. Lines of the 2ν9-ν9 hot band were also assigned and included in our analysis of the bending region. This data will be useful in identifying isotopic propane lines in Titan and other astrophysical objects.

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Section: Discussionmentioning

confidence: 75%

Section: Discussionmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

First high-resolution infrared spectra of 2–13C-propane: Analyses of the ν26 (B2) c-type and ν9 (A1) b-type bands

Daunt

Grzywacz

Western

et al. 2020

Journal of Molecular Structure

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First high resolution infrared spectra of 1-13C-Propane analyses of the ν26 (B2) C-Type, ν8 (A1) and ν9 (A1) B-Type bands

Daunt

Grzywacz

Western

et al. 2023

Journal of Molecular Spectroscopy

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VIBFREQ1295: A New Database for Vibrational Frequency Calculations

Trujillo

McKemmish

2022

J. Phys. Chem. A

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High-throughput approaches for producing approximate vibrational spectral data for molecules of astrochemistry interest rely on harmonic frequency calculations using computational quantum chemistry. However, model chemistry recommendations (i.e., a level of theory and basis set pair) for these calculations are not yet available and, thus, thorough benchmarking against comprehensive benchmark databases is needed. Here, we present a new database for vibrational frequency calculations (VIBFREQ1295) storing 1295 experimental fundamental frequencies and CCSD(T)(F12*)/cc-pVDZ-F12 ab initio harmonic frequencies from 141 molecules. VIBFREQ1295’s experimental data was complied through a comprehensive review of contemporary experimental data, while the ab initio data was computed here. The chemical space spanned by the molecules chosen is considered in-depth and is shown to have good representation of common organic functional groups and vibrational modes. Scaling factors are routinely used to approximate the effect of anharmonicity and convert computed harmonic frequencies to predicted fundamental frequencies. With our experimental and high-level ab initio data, we find that a single global uniform scaling factor of 0.9617(3) results in median differences of 15.9(5) cm–1. A far superior performance with a median difference of 7.5(5) cm–1 can be obtained, however, by using separate scaling factors (SFs) for three regions: frequencies less than 1000 cm–1 (SF = 0.987(1)), between 1000 and 2000 cm–1 (SF = 0.9727(6)), and above 2000 cm–1 (SF = 0.9564(4)). This sets a lower bound for the performance that could be reliably obtained using scaling of harmonic frequency calculations to predict experimental fundamental frequencies. VIBFREQ1295’s most important purpose is to provide a robust database for benchmarking the performance of any vibrational frequency calculations. VIBFREQ1295 data could also be used to train machine-learning models for the prediction of vibrational spectra and as a reference and data starting point for more detailed spectroscopic modeling of particular molecules. The database can be found as part of the Supporting Information for this paper or in the Harvard DataVerse at .

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Investigation of the ν₈and ν₂₁bands of propane CH₃CH₂CH₃at 11.5 and 10.9 µm: evidence of large amplitude tunnelling effects

Abstract: Investigation of the nu8 and nu21 bands of propane CH3CH2CH3 at 11.5 and 10.9 µm: evidence of large amplitude tunnelling effects.

Cited by 5 publications

References 43 publications

First high-resolution infrared spectra of 2–13C-propane: Analyses of the ν26 (B2) c-type and ν9 (A1) b-type bands

First high-resolution infrared spectra of 2–13C-propane: Analyses of the ν26 (B2) c-type and ν9 (A1) b-type bands

First high resolution infrared spectra of 1-13C-Propane analyses of the ν26 (B2) C-Type, ν8 (A1) and ν9 (A1) B-Type bands

VIBFREQ1295: A New Database for Vibrational Frequency Calculations

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