scholarly journals The electronic spectra of acetaldehyde-h4 and -d4

1992 ◽  
Vol 70 (3) ◽  
pp. 931-934 ◽  
Author(s):  
N. N. Yakovlev ◽  
I. A. Godunov
Keyword(s):  
Barrier Height ◽  
Room Temperature ◽  
Electronic Absorption Spectra ◽  
Energy Levels ◽  
Vapour Phase ◽  
Electronic Transitions ◽  
Torsional Barrier ◽  
Bending Mode ◽  
Out Of Plane ◽  
Plane Bending

The [Formula: see text] electronic absorption spectra of acetaldehyde-h4 and -d4 were recorded in the vapour phase at room temperature. The major experimental requirement was a high pressure × path length (650 Torr × 140 m). The vibrational structure of these electronic transitions was interpreted in terms of the torsional modes [Formula: see text] and [Formula: see text] attached to the [Formula: see text] out-of-plane bending mode. The main CH3CHO results agreed with those obtained earlier (Moule and Ng); the values of the [Formula: see text] transition and torsional barrier height were 27240.1 and 590 cm−1 respectively. Three inversion (out-of-plane bending) energy levels in the excited [Formula: see text] state were found and the inversion potential function was determined with a barrier height of 1110 cm−1. The CD3CDO spectrum confirmed the CH3CHO analysis. The values of the [Formula: see text] transition and torsional barrier height were equal to 27270 and 610 cm−1. Keywords: vibronic spectrum, acetaldehyde, molecular structure.

Optical–optical double resonance study of the and &([a-z]+);(3A2) states of thiophosgene

1994 ◽  
Vol 72 (3) ◽  
pp. 745-757 ◽  
Author(s):  
Benoit Simard ◽  
Valerie J. Mackenzie ◽  
Peter A. Hackett ◽  
Ronald P. Steer
Keyword(s):  
Barrier Height ◽  
Energy Levels ◽  
Double Resonance ◽  
The Other ◽  
Bending Angle ◽  
Optical Double Resonance ◽  
Out Of Plane ◽  
State Potential ◽  
Minimum Potential ◽  
Plane Bending

The &([a-z]+);(3A2) and [Formula: see text] states of jet-cooled thiophosgene (Cl2CS) have been studied by optical–optical double resonance (OODR) spectroscopy. Two OODR schemes have been used to probe the [Formula: see text] state. One scheme uses selected vibronic levels of the &([a-z]+);(1A2) state as the intermediate state, while the other uses the vibrationless and 2131 levels of the &([a-z]+);(3A2) state. All of the vibronic levels in the 33 980−35 600 cm−1 region can be rationalized with the following origin band and fundamentals: 0° = 34 277 cm−1, v1 = 505 cm−1, v2 = 470 cm−1, v3 = 213 cm−1, v6 = 249 cm−1, 42 = 341 cm−1, 44 = 627 cm−1. The discrepancies among the various studies of the [Formula: see text] state will be discussed and reconciled. It is conjectured that the [Formula: see text] state potential along the C—S coordinate exhibits an asymmetric double-minimum potential resulting from the interaction of the 1A1 states arising from the [Formula: see text] configurations. The minimum corresponding to the [Formula: see text] configuration lies higher in energy and the principal decay mechanism for molecules pumped to its first few vibronic levels is fluorescence. On the other hand, molecules pumped to the minimum corresponding to the nominal [Formula: see text] configuration decay nonradiatively. The barrier height to inversion and the out-of-plane bending angle along the out-of-plane bending coordinate, v4, have been determined to be 945 cm−1 and 25°, respectively, by fitting quartic-quadratic and quadratic-Gaussian double-minimum potentials to the observed energy levels. The &([a-z]+);(3A2) state has been studied by a novel OODR scheme which uses the fluorescent vibrationless level of the [Formula: see text] state to monitor [Formula: see text]transitions. A vibronic analysis has been carried out and the following origin band and fundamentals derived for the &([a-z]+);(3A2) state: 0° = 17 499 cm−1, v1 = 923 cm−1, v2 = 474 cm−1, v3 = 247 cm−1, 42 = 297 cm−1, 44 = 560 cm−1, 46 = 741 cm−1. With the exception of a few corrections and additions, the results confirm the findings of previous studies, notably regarding the bent geometry and barrier height to inversion. An overall comparison of the data suggests that the wavenumber of v6 in theÃ(1A2) state is 279 cm−1 instead of 189 cm−1.

scholarly journals The conformational changes accompanying the triplet–singlet electronic excitation of acetaldehyde, CH3CHO

1985 ◽  
Vol 63 (7) ◽  
pp. 1378-1381 ◽  
Author(s):  
D. C. Moule ◽  
K. H. K. Ng
Keyword(s):  
Conformational Changes ◽  
Room Temperature ◽  
Electronic Excitation ◽  
Vapour Phase ◽  
Torsional Mode ◽  
Methyl Group ◽  
Bending Mode ◽  
Out Of Plane ◽  
The Many ◽  
Franck Condon

The first electronic absorption system of acetaldehyde was recorded in the vapour phase at room temperature. The many-banded spectrum proved to be very complex and it was only at the extreme red edge of the absorption that the pattern became simple enough to analyze. The major experimental requirement was a high pressure × path length (500 Torr × 168 m). Spectra were interpreted in terms of the torsional mode ν′15 and ν″15 attached to the ν′14 out-of-plane bending mode. Both modes were highly Franck–Condon active and the [Formula: see text] band at 27240.4 cm−1 was not directly observed. The barrier to rotation of the methyl group was 618.5 cm−1. More surprising was the observation that the methyl group undergoes a rotation from a [Formula: see text] eclipsed configuration to a staggered configuration. The intensity of the ν′14 quantum addition and its position in the spectrum suggest that the aldehydic hydrogen is nonplanar in the ã state.

The effect of intermolecular forces upon the vibrations of molecules in the crystalline state I. The out-of-plane bending of the carbonate ion in aragonite minerals

1963 ◽  
Vol 275 (1362) ◽  
pp. 295-309 ◽  
Keyword(s):  
Intermolecular Forces ◽  
Absolute Intensities ◽  
Carbonate Ion ◽  
Nearest Neighbours ◽  
Bending Mode ◽  
Infra Red ◽  
Out Of Plane ◽  
Plane Bending ◽  
Oxygen Bond ◽  
Dipole Energy

The infra-red absorption of polycrystalline BaCO 3 , SrCO 3 , and CaCO 3 , the latter in both the aragonite and calcite modifications, has been measured in the region 600 to 2000 cm -1 . Absolute intensities were determined for each of the three fundamental bands of the carbonate ion, by the method of extrapolation to infinite dilution of the carbonate in the alkali halide matrix. The band due to the out-of-plane bending mode was examined under high resolution, the samples employed having been enriched to a 50/50 ratio of 12 C/ 13 C. Intermolecular coupling in this band, which is revealed by the isotopic solid solution, has been interpreted as arising primarily from interaction of the dipoles produced during the vibration. The dipole derivatives calculated from this coupling agree fairly well with those estimated from the absolute intensities. Various sources of error are discussed, and in particular, an estimate is made of the dipole-dipole energy summed over the entire lattice, instead of merely for nearest neighbours. The carbon-oxygen bond moment during the vibration has an effective value of from 1.3 to 1.7 debyes.

Rotational transitions within the 21, 31, 41, and 61 states of formaldehyde H212C16O This article is part of a Special Issue on Spectroscopy at the University of New Brunswick in honour of Colan Linton and Ron Lees.

2009 ◽  
Vol 87 (5) ◽  
pp. 425-435 ◽  
Author(s):  
L. Margulès ◽  
A. Perrin ◽  
R. Janečkovà ◽  
S. Bailleux ◽  
C. P. Endres ◽  
...  
Keyword(s):  
Energy Levels ◽  
Ground Vibration ◽  
Chem Phys ◽  
Vibrational States ◽  
Millimetre Wave ◽  
Rotational Spectra ◽  
Wave Measurements ◽  
Bending Mode ◽  
Out Of Plane ◽  
Rotational Transitions

This work, besides its fundamental interest, is motivated by the atmospheric and astrophysical importance of formaldehyde (H2CO). The goal of this study is to complete the already existing list of rotational transitions within the ground vibration state by a list of transitions within the four first excited 21, 31, 41, and 61 vibrational states, to help the detection of this species by microwave or millimetre wave techniques. For this purpose, the rotational spectra of H2CO in the 21, 31, 41, and 61 excited vibrational states have been investigated in Lille and Cologne in the millimetre region at 160–600 GHz and 850–903 GHz, respectively. The results of these millimetre wave measurements were combined with the 21, 31, 41, and 61 infrared energy levels, which were obtained from previous analysis of FTS spectra of the ν4 (out of plane bending mode), ν6 (CH2 rock mode), and ν3 (CH2 bending mode) bands recorded in the 10 µm region (D.C. Reuter, S. Nadler, S.J. Daunt, and J.W.C. Johns. J. Chem. Phys. 91, 646 (1989)) and more recently for the ν2 fundamental band (C=O stretching, located at 1746.009 cm–1) (F. Kwabia Tchana, A. Perrin, and N. Lacome. J. Mol. Spectrosc. 245, 141, (2007)). The energy level calculation of the 21, 31, 41, and 61 interacting states accounts for the various Coriolis-type resonances that perturb the energy levels of the 21, 31, 41, and 61 vibrational states as well as for the anharmonic resonances coupling the 21 and 31 energy levels, and in this way the microwave and infrared data could be reproduced within their associated experimental uncertainty. However, it is clear that the theoretical model used to account for the very large A-type Coriolis resonance linking the 41 and 61 energy levels of H2CO is only effective with poor physical meaning.

Inversion/out-of-plane bending rovibrational energy levels of partially deuterated SiH3, CH3, CH3+, and NH3+

1992 ◽  
Vol 153 (1-2) ◽  
pp. 285-287 ◽  
Author(s):  
V. Špirko ◽  
W.P. Kraemer
Keyword(s):  
Energy Levels ◽  
Out Of Plane ◽  
Plane Bending

Large Amplitude Oscillations of Thin Circular Rings

1987 ◽  
Vol 54 (2) ◽  
pp. 315-322 ◽  
Author(s):  
S. P. Maganty ◽  
W. B. Bickford
Keyword(s):  
Large Amplitude ◽  
Multiple Scales ◽  
Equations Of Motion ◽  
Circular Ring ◽  
Bending Mode ◽  
Out Of Plane ◽  
Circular Rings ◽  
Linear Problems ◽  
Plane Bending ◽  
Nonlinear Equations Of Motion

Using an intrinsic formulation, an accurate set of geometrically nonlinear equations of motion is derived for the large amplitude oscillations of a thin circular ring. Non-dimensionalization of the equations of motion and the compatibility conditions indicates clearly that certain terms involving the extensional deformation, the shear deformation, and the rotatory inertia are relatively small and can be discarded. The resulting equations of motion are analyzed by the method of multiple scales with a single bending mode approximation to the linear problems indicating a softening type of nonlinearity for both the in-plane and the out-of-plane problems with the out-of-plane flexural motion experiencing a greater degree of softening when compared to that of the in-plane flexural motion. The results for the nonresonant case indicate that the frequency of an out-of-plane bending mode is significantly reduced by the presence of a nonzero in-plane bending amplitude, whereas the results for the resonant case indicate the presence of unsteady oscillations with an exchange of energy between the in-plane and the out-of-plane modes.

Optical properties of HgS and HgS : Co2+ crystals

1991 ◽  
Vol 6 (12) ◽  
pp. 2677-2679 ◽  
Author(s):  
Sung-Hyu Choe ◽  
Ki-Su Yu ◽  
Jae-Eun Kim ◽  
Hae Yong Park ◽  
Wha-Tek Kim
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Room Temperature ◽  
Energy Levels ◽  
Band Gaps ◽  
Electronic Transitions ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Optical Absorption Spectra ◽  
Coupling Parameters

Melt-grown crystals of HgS and HgS : Co2+ were used to measure their optical absorption spectra. The optical energy band gaps of these crystals were 2.030 eV and 1.870 eV at room temperature, respectively. The impurity optical absorption peaks of Co2+ were observed at 4030, 5988, 12285, 12672, and 12905 cm−1. These peaks can be attributed to the electronic transitions between the split energy levels of Co2+ ion located at the Td symmetry site, where the crystal field, Racah, and spin-orbit coupling parameters were given by Dq = 403, B = 427, and Λ = −155 cm−1, respectively.

Coupling of the Out‐of‐Plane Bending Mode in Nitrates and Carbonates of the Aragonite Structure

1955 ◽  
Vol 23 (7) ◽  
pp. 1290-1294 ◽  
Author(s):  
J. C. Decius
Keyword(s):  
Bending Mode ◽  
Out Of Plane ◽  
Plane Bending

Selenoketone spectroscopy: vibronic analysis of the and n → π electronic transitions in F2CSe

1983 ◽  
Vol 61 (8) ◽  
pp. 1743-1748 ◽  
Author(s):  
M. Y. Bölük ◽  
D. C. Moule ◽  
D. J. Clouthier
Keyword(s):  
Energy Levels ◽  
Vibrational Analysis ◽  
Wavelength Region ◽  
Electronic Transitions ◽  
Vibrational Assignments ◽  
Continuous Structure ◽  
Out Of Plane ◽  
Minimum Potential ◽  
Vibronic Analysis

The spectrum of F2CSe has been surveyed over the 700–200 nm wavelength region and three distinct absorptions identified. These are the spin-allowed, [Formula: see text] and spin-forbidden [Formula: see text] overlapping n → π* transitions, λmax = 434 nm, and the orbitally-allowed [Formula: see text] transition, λmax = 236 nm. Vibrational assignments for the band systems have been made and the out-of-plane energy levels analyzed in terms of a quadratric-Lorentzian double minimum potential. The barriers to inversion for the Ã1A2/ã3A2 states were found to be 2483/2923 cm−1 and the out-of-plane angles 30.1/31.4 deg. The singlet–triplet separation was E(Ã1A2) − E(ã3A2) = 671 cm−1 The [Formula: see text], system displays continuous structure and was not subject to a vibrational analysis.

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