Vibrational and rotational spectroscopy of (CD3OD)-C-13 (original) (raw)
CCSD(T) Study of CD 3 –O–CD 3 and CH 3 –O–CD 3 Far-Infrared Spectra
The Journal of Physical Chemistry A, 2012
From a vibrationally corrected 3D potential energy surface determined with highly correlated ab initio calculations (CCSD(T)), the lowest vibrational energies of two dimethyl-ether isotopologues, 12 CH 3 -16 0-12 CD 3 (DMEd 3 ) and 12 CD 3 -16 0-12 CD 3 (DME-d 6 ), are computed variationally. The levels that can be populated at very low temperatures correspond to the COC-bending and the two methyl torsional modes. Molecular symmetry groups are used for the classification of levels and torsional splittings. DME-d 6 belongs to the G 36 group, as the most abundant isotopologue 12 CH 3 -16 0-12 CH 3 (DME-iiJ, while DME-A, is a G 18 species. Previous assignments of experimental Raman and far-infrared spectra are discussed from an effective Hamiltonian obtained after refining the ab initio parameters. Because a good agreement between calculated and experimental transition frequencies is reached, new assignments are proposed for various combination bands corresponding to the two deuterated isotopologues and for the 020 ->• 030 transition of DME-d 6 . Vibrationally corrected potential energy barriers, structural parameters, and anharmonic spectroscopic parameters are provided. For the 3N -9 neglected vibrational modes, harmonic and anharmonic fundamental frequencies are obtained using second-order perturbation theory by means of CCSD and MP2 force fields. Fermi resonances between the COC-bending and the torsional modes modify DME-d 3 intensities and the band positions of the torsional overtones.
Journal of the Optical Society of America B, 1994
High-resolution Fourier-transform spectra of the lower vibrational fundamentals of the 13CD 3 OH isotopomer of methanol are under investigation in the 800-1350-cm-1 region, including the vs in-plane CD 3 -rocking (A'), V7 CO-stretching (A'), V5 CD 3 -deformation (A'), and V4 OH-bending (A') bands. The torsion-vibration-rotation energy-level manifold for these lower modes displays numerous perturbations that are due to torsion-vibration interactions and contains a variety of features of interest in the excited-state energy-level patterns. Analyses of the bands show that there are major problems in formulating effective Hamiltonians and in determining reliable molecular constants for the excited states because of strong torsion-vibration coupling. Assignments for five far-infrared laser transition systems have been deduced; these involve the CD 3 -rocking, CO-stretching, and CD 3 -deformation states.
Electric field effects on roto-vibrational transitions of13CD3OH1
International Journal of Infrared and Millimeter Waves, 1995
We used a Stark-Optoacoustic cell and hybrid waveguide resonators to perform an Infrared and Far Infrared Stark Spectroscopy study on some transitions of 13CD3OH. Different behaviours of the transitions in the presence of a d.c. electric field were observed. The Stark splittings of six FIR laser lines ranging from 34 to 136 MHz/kVcm -I were determined. The analysis of the behaviour of the IR and FIR transitions in the presence of the external electric fields gives important and exclusive information on the levels involved in the transitions.
The Journal of Chemical Physics, 1983
We report the detection of 17 pure rotation transitions in the ground vibronic state of the CD, radical using far infrared laser magnetic resonance spectroscopy. Fitting the data using an effective rotational Hamiltonian yields values for the three rotational constants, seven centrifugal distortion constants, the three electronic spin-rotation. and two electronic spin-spin parameters. We also fit this data, and CD, v 2 band data (published separately), using the semirigid bender Hamiltonian and obtain the effective bending potential function for CD,. Combining this with previous CH, results enables us to predict the rotation bending energy levels of CHD. We also report here the detection of two further rotational transitions in the v I excited vibrational state ofCH,.
Fourier Transform Infrared Spectroscopy and Vibrational Coupling in the OH-Bending Band of13CH3OH
Journal of Molecular Spectroscopy, 1998
We present in this work a high-resolution Fourier transform infrared study of the OH-bending vibrational band of 13 CH 3 OH. We have investigated the 1070-1400 cm Ϫ1 spectral region at 0.002 cm Ϫ1 resolution using the modified Bomem DA3.002 Fourier transform spectrometer at the Steacie Institute for Molecular Sciences at the National Research Council of Canada in Ottawa. This study has led to (i) determination of excited-state J(J ϩ 1) subband expansion coefficients and (ii) characterization of a variety of interactions coupling the different vibrational modes, notably a strong Fermi resonance between the OH bend and the torsionally excited CH 3-rocking mode. The OH-bending band is widely spread with Q subbranches grouped in two peaks at about 1312 and 1338 cm Ϫ1. The lower levels for all assigned subbands were confirmed using closed loops of IR and FIR transitions. The subbands have been fitted to J(J ϩ 1) power-series expansions in order to obtain the subband origins and the state-specific energy expansion coefficients for both the OH-bending and excited torsional CH 3-rocking states. The strong interaction between the OH-bending state and the first excited torsional CH 3-rocking state gives rise to several "extra" forbidden subbands due to intensity borrowing. The asymmetry splitting of the (nK) v ϭ (122) OH A OH-bending doublet was found to be anomalously small, and the splitting of the (122) r A CH 3-rocking doublet is observed to be enhanced. We have identified a network of intermode interactions causing this unusual behavior, but a quantitative analysis of the vibrational coupling is restricted by limited knowledge of the unperturbed positions of the interacting levels. All these interactions provide relaxation channels for intramolecular vibrational redistribution among the lower vibrational modes in 13 CH 3 OH. Another important finding is that the torsion-K-rotation energy curves in the OH-bending state display an inverted pattern compared to the ground state.
High-Resolution Infrared Spectroscopy of DC3N in the Stretching Region
Proceedings of the 2021 International Symposium on Molecular Spectroscopy, 2021
The perspectives opened by modern ground-based infrared facilities and the forthcoming James Webb Telescope mission have brought a great attention to the rovibrational spectra of simple interstellar molecules. In this view, and because of the lack of accurate spectroscopic data, we have investigated the infrared spectrum of deuterated cyanoacetylene (DC 3 N), a relevant astrochemical species. The ] 1 , ] 2 , and ] 3 fundamentals as well as their hot-bands were observed in the stretching region (1,500-3,500 cm −1) by means of a Fourier transform infrared spectrometer. Supplementary measurements were performed at millimeter-wavelengths (243-295 GHz) with a frequency-modulation spectrometer equipped with a furnace, that allowed to probe pure rotational transitions in the investigated stretching states. Furthermore, since HC 3 N is observed as by-product in our spectra and suffers from the same deficiency of accurate infrared data, its rovibrational features have been analyzed as well. The combined analysis of both rotational and ro-vibrational data allowed us to determine precise spectroscopic constants that can be used to model the infrared spectra of DC 3 N and HC 3 N. The importance of accurate molecular data for the correct modeling of proto-planetary disks and exoplanetary atmospheres is then discussed.
Precision spectroscopy and comprehensive analysis of perturbations in the A1∏(v= 0) state of13C18O
Molecular Physics, 2018
We have reinvestigated the A 1 Π(v = 0) level of 13 C 18 O using new high-resolution spectra obtained via multi-photon laser excitation as well as with synchrotron-based Fourier-transform absorption spectroscopy of the A 1 Π -X 1 Σ + (0, 0), e 3 Σ --X 1 Σ + (1, 0), d 3 ∆ -X 1 Σ + (4, 0), a 3 Σ + -X 1 Σ + (9, 0), and a 3 Π -X 1 Σ + (11, 0) bands. In addition, Fourier-transform emission spectroscopy in the visible range is performed on the B 1 Σ + -A 1 Π(0, 0) band. Spectra of the B 1 Σ + -X 1 Σ + (0, 0) band are measured in order to tie information from the latter emission data to the level structure of A 1 Π(v = 0). The high pressures in the absorption cell at the synchrotron and the high temperatures in the emission discharge permitted monitoring of high rotational quantum levels in A 1 Π(v = 0) up to J = 43. All information, in total over 900 spectral lines, was included in an effective-Hamiltonian analysis of the A 1 Π(v = 0, J) levels that are directly perturbed by the e 3 Σ 0, 1) close-lying levels and the e 3 Σ -(v = 0, 2), d 3 ∆(v = 3, 5), a 3 Σ + (v = 8, 10) remote levels, as well being indirectly influenced by the a 3 Π(v = 10, 11) state. The influence of nine further perturber levels and their interactions was investigated and are not significant for reproducing the present experimental data. This analysis leads to a much improved description in terms of molecular constants and interaction parameters, compared to previous studies of the same energy region for other CO isotopologues.
Rotational and rovibrational spectroscopy of the v 8 = 1 and 2 vibrational states of CH 3 NC
Molecular Physics, 2011
The lowest frequency vibration-rotation band ν , corresponding to the degenerate CNC bending vibration of methyl isocyanide (CH 3 NC) with band center at 267.3 cm-1 , was studied by FTIR spectroscopy between 215 and cm-1 and rotational spectroscopy in the range from 201 to 383 GHz in order to describe the vibration-rotation dynamics with inclusion of all important anharmonic and vibration-rotation interactions. Assignments extended to higher-K rotational states in both vibration-rotation and rotational spectra reveal a resonance crossing with the v 8 = 2 overtone level due to a local anharmonic Fermi resonance. The simultaneous analysis of both types of data provides a fully quantitative reproduction of the experimental data as well as a preliminary characterization of the v 8 = 2 level. The parallel component of the overtone band 0 8 2ν with band center at 524.6 cm-1 was assigned for the first time from spectra in the region from 480 to 585 cm-1 together with the hot bands 8 8 2ν ν − in the region of the fundamental band.
Journal of Molecular Spectroscopy, 1987
A third-order theory of the intensities of the allowed and "forbidden" (perturbation-allowed) transitions to the fundamental vibrational levels of C,, semirigid molecules has been worked out by using the method of contact transformations applied to the electric dipole moment operator. Explicit expressions have been obtained for the linestrengths of the allowed (Ak = 0, ? 1) as well as forbidden (Ak = 52, +3, +4) transitions from the ground vibronic state to the fundamental vibrational levels of C,, molecules. The treatment takes into account all the important Coriolis and anharmonic interactions in a C,, molecule, including the effect of the "2, 2" and "2, -1" l-type interactions and the Ak = +3 interactions on the intensities of the allowed and forbidden vibrational-rotational transitions. The expressions for the linestrengths of the allowed and forbidden transitions are given here in a form suitable to fit the experimental data on the intensities in the vibrational-rotational spectra of C,, molecules. 0 1987 Academic prrss, IX.