Infrared Laser Spectroscopy of the ν4and ν9Band System of CH2F37Cl

Baldacci, A.; Stoppa, Paolo; Giorgianni, S.; Ghersetti, S.

doi:10.1006/jmsp.1998.7770

Cited by 7 publications

(3 citation statements)

References 9 publications

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“…However, should only a quartic force field be available, then CVPT2 often outperforms more sophisticated VCI models, due to fortuitous error cancellation that arises from simultaneously truncating both the perturbation theory and potential energy surface expansions. 1090.1264 0.0002 [8] 761.4403 0.0004 [13] 717.4675 0.0005 [21] 1111.5162 0.0002 [8] 1002.3349 0.0004 [11] 759.8486 0.0005 [21] 1178.6414 0.0002 [8] 1067.7991 0.0004 [14] 898.6648 0.005 [18] 1255.8285 0.0002 [8] 1236.8219 0.0010 [10] 1153 d 1.5 [16] 1435.6357 0.0002 [6] 1353.3173 0.0008 [9] 1268.8514 0.0005 [22] 1509.1492 0.0002 [6] 1473.6 0.5 [12] 1435.0 0.2 [17] 2947.9 a > 1 [7] a An uncertain assignment, based on a Q-branch feature that should be B-type and have no central Q branch. The uncertainty could be several cm -1 .…”

Section: Discussionmentioning

confidence: 99%

“…Fluoro-and chloro-substituted derivatives of methane play major roles in the chemistry and spectroscopy of the Earth's atmosphere and thus have attracted considerable attention from researchers. In particular, the vibrational and ro-vibrational spectra of difluoromethane, [1][2][3][4][5][6][7][8] fluorochloromethane [9][10][11][12][13][14] and dichloromethane [15][16][17][18][19][20][21][22][23] have been measured and assigned by group frequency theoretical analysis and parameterizing model Hamiltonians. Their equilibrium semi-experimental structures have also been obtained.…”

Section: Introductionmentioning

confidence: 99%

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Comparing the accuracy of perturbative and variational calculations for predicting fundamental vibrational frequencies of dihalomethanes

Krasnoshchekov

Schutski

Craig

et al. 2018

The Journal of Chemical Physics

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Three dihalogenated methane derivatives (CHF, CHFCl, and CHCl) were used as model systems to compare and assess the accuracy of two different approaches for predicting observed fundamental frequencies: canonical operator Van Vleck vibrational perturbation theory (CVPT) and vibrational configuration interaction (VCI). For convenience and consistency, both methods employ the Watson Hamiltonian in rectilinear normal coordinates, expanding the potential energy surface (PES) as a Taylor series about equilibrium and constructing the wavefunction from a harmonic oscillator product basis. At the highest levels of theory considered here, fourth-order CVPT and VCI in a harmonic oscillator basis with up to 10 quanta of vibrational excitation in conjunction with a 4-mode representation sextic force field (SFF-4MR) computed at MP2/cc-pVTZ with replacement CCSD(T)/aug-cc-pVQZ harmonic force constants, the agreement between computed fundamentals is closer to 0.3 cm on average, with a maximum difference of 1.7 cm. The major remaining accuracy-limiting factors are the accuracy of the underlying electronic structure model, followed by the incompleteness of the PES expansion. Nonetheless, computed and experimental fundamentals agree to within 5 cm, with an average difference of 2 cm, confirming the utility and accuracy of both theoretical models. One exception to this rule is the formally IR-inactive but weakly allowed through Coriolis-coupling H-C-H out-of-plane twisting mode of dichloromethane, whose spectrum we therefore revisit and reassign. We also investigate convergence with respect to order of CVPT, VCI excitation level, and order of PES expansion, concluding that premature truncation substantially decreases accuracy, although VCI(6)/SFF-4MR results are still of acceptable accuracy, and some error cancellation is observed with CVPT2 using a quartic force field.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparing the accuracy of perturbative and variational calculations for predicting fundamental vibrational frequencies of dihalomethanes

Krasnoshchekov

Schutski

Craig

et al. 2018

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The availability of pure isotopic species simplifies the analysis and improves to a large degree the accuracy of the fitted spectroscopic parameters of the investigated systems. An example is given by the spectrum of CH 2 37 ClF [1] where the complex structure of the m 4 and m 9 bands has been fully interpreted and modelled. In the case of compounds with 79/81 Br atoms the problem of a correct interpretation is even worse since the generated spectra are very dense due to the smallness of the rotational constants.…”

Section: Introductionmentioning

confidence: 99%