The interplay of VSCF/VCI calculations and matrix-isolation IR spectroscopy – Mid infrared spectrum of CH3CH2F and CD3CD2F

Dinu, Dennis F.; Ziegler, Benjamin; Podewitz, Maren; Liedl, Klaus R.; Loerting, Thomas; Grothe, Hinrich; Rauhut, Guntram

doi:10.1016/j.jms.2019.111224

Cited by 23 publications

(13 citation statements)

References 35 publications

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“…While the former correspond to parameters obtained from atomic positions averaged over the VCI ground state wavefunction, the latter are instantaneous inter-nuclear distances calculated from an expectation value of the bond lengths expanded in terms of the normal coordinates. As is typically observed (Czakó et al, 2009;Dinu et al, 2020), both sets of vibrationally averaged bond lengths differ substantially from each other with the largest absolute difference of 0.0169 Å observed for r(NH 3 ) in the main isotopologue. The CNH angle α(C 2 NH 3 ) shows a slightly larger vibrational effect compared to other angles, in line with the inversion character of this coordinate.…”

Section: Geometrical Parameters Rotational Constants and Dipole Momsupporting

confidence: 52%

High-Level Rovibrational Calculations on Ketenimine

2021

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From an astrochemical point of view ketenimine (CH2CNH) is a complex organic molecule (COM) and therefore likely to be a building block for biologically relevant molecules. Since it has been detected in the star-forming region Sagittarius B2(N), it is of high relevance in this field. Although experimental data are available for certain bands, for some energy ranges such as above 1200 cm−1 reliable data virtually do not exist. In addition, high-level ab initio calculations are neither reported for ketenimine nor for one of its deuterated isotopologues. In this paper, we provide for the first time data from accurate quantum chemical calculations and a thorough analysis of the full rovibrational spectrum. Based on high-level potential energy surfaces obtained from explicitly correlated coupled-cluster calculations including up to 4-mode coupling terms, the (ro)vibrational spectrum of ketenimine has been studied in detail by variational calculations relying on rovibrational configuration interaction (RVCI) theory. Strong Fermi resonances were found for all isotopologues. Rovibrational infrared intensities have been obtained from dipole moment surfaces determined from the distinguishable cluster approximation. A comparison of the spectra of the CH2CNH molecule with experimental data validates our results, but also reveals new insight about the system, which shows very strong Coriolis coupling effects.

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Section: Geometrical Parameters Rotational Constants and Dipole Momsupporting

confidence: 52%

High-Level Rovibrational Calculations on Ketenimine

2021

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“…Table 4 shows that this statement holds true also in a bigger context when we consider our previous Ne and Ar MI-IR studies on water 10 and fluoroethane. 131 The matrix effects depend on the specific host-guest combination.…”

Section: Matrix Effects In Various Host-guest Combinationsmentioning

confidence: 99%

Decomposing anharmonicity and mode-coupling from matrix effects in the IR spectra of matrix-isolated carbon dioxide and methane

Dinu

Podewitz

Grothe

et al. 2020

Phys. Chem. Chem. Phys.

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“…We performed multiple MI-IR experiments on stable, small molecules, such as water [29], carbon dioxide, and methane [30], fluoroethane [74], methanol, and others. In all those studies, we use argon and neon as host systems and utilize various dilutions and temperature changes to learn about the influence of matrix effects.…”

Section: Case Studies On the Synergy Of Mi-ir And Vscf/ Vcimentioning

confidence: 99%

“…Considering fluoroethane (ethyl fluoride, HFC-161), we have exemplified an application of the interplay of MI-IR and VSCF/VCI [74]. HFC-161 is a hydrofluorocarbon increasingly used in refrigerant mixtures.…”

Section: Fluoroethane: Elucidation Of the Ch Stretch Regionmentioning

confidence: 99%

On the synergy of matrix-isolation infrared spectroscopy and vibrational configuration interaction computations

et al. 2020

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The key feature of matrix-isolation infrared (MI-IR) spectroscopy is the isolation of single guest molecules in a host system at cryogenic conditions. The matrix mostly hinders rotation of the guest molecule, providing access to pure vibrational features. Vibrational self-consistent field (VSCF) and configuration interaction computations (VCI) on ab initio multimode potential energy surfaces (PES) give rise to anharmonic vibrational spectra. In a single-sourced combination of these experimental and computational approaches, we have established an iterative spectroscopic characterization procedure. The present article reviews the scope of this procedure by highlighting the strengths and limitations based on the examples of water, carbon dioxide, methane, methanol, and fluoroethane. An assessment of setups for the construction of the multimode PES on the example of methanol demonstrates that CCSD(T)-F12 level of theory is preferable to compute (a) accurate vibrational frequencies and (b) equilibrium or vibrationally averaged structural parameters. Our procedure has allowed us to uniquely assign unknown or disputed bands and enabled us to clarify problematic spectral regions that are crowded with combination bands and overtones. Besides spectroscopic assignment, the excellent agreement between theory and experiment paves the way to tackle questions of rather fundamental nature as to whether or not matrix effects are systematic, and it shows the limits of conventional notations used by spectroscopists.

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The interplay of VSCF/VCI calculations and matrix-isolation IR spectroscopy – Mid infrared spectrum of CH3CH2F and CD3CD2F

Cited by 23 publications

References 35 publications

High-Level Rovibrational Calculations on Ketenimine

High-Level Rovibrational Calculations on Ketenimine

Decomposing anharmonicity and mode-coupling from matrix effects in the IR spectra of matrix-isolated carbon dioxide and methane

On the synergy of matrix-isolation infrared spectroscopy and vibrational configuration interaction computations

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