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.

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 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.

Thioamide spectroscopy: long path length absorption and quantum chemical studies of thioformamide vapour, CHSNH2/CHSND2

1987 ◽  
Vol 65 (9) ◽  
pp. 2100-2105 ◽  
Author(s):  
R. H. Judge ◽  
D. C. Moule ◽  
J. D. Goddard
Keyword(s):  
Path Length ◽  
Lower State ◽  
Amino Groups ◽  
Vibrational Assignments ◽  
Transition Formula ◽  
Out Of Plane ◽  
Chemical Studies ◽  
Moderate Resolution ◽  
Quantum Chemical Studies ◽  
Franck Condon

The 270 nm absorption spectra of thioformamide, CHSNH2 and CHSND2, have been photographically recorded under conditions of long path length (88 m) and moderate resolution (7.5 Å/mm). The absorption was assigned to the electron promotion, nS → π* (CS), and to the electronic transition, [Formula: see text]. The spectra proved to be complex, highly congested and somewhat diffuse which limited the extent of the vibrational assignments. Progressions in five members were observed in both CHSNH2/CHSND2 in intervals of 516/496 cm−1 which were assigned to ν10, the out-of-plane aldehyde wagging mode. It was concluded on Franck–Condon grounds that the [Formula: see text] molecule was non-planar at the aldehyde center. Structures and vibrational frequencies were calculated for the [Formula: see text] and the[Formula: see text] electronic states at the 3-21G* SCF level. The calculations confirmed that the lower state was strictly planar and predicted that both the aldehyde and amino groups were pyramidal in the upper electronic state.

Semi-empirical Molecular Orbital Energy Levels of the Hexammine and Chloroammine Complexes of Co(IV)

1967 ◽  
Vol 22 (2) ◽  
pp. 170-175 ◽  
Author(s):  
Walter A. Yeranos ◽  
David A. Hasman
Keyword(s):  
Molecular Orbital ◽  
Energy Levels ◽  
Empirical Evaluation ◽  
Wave Functions ◽  
Electronic Transitions ◽  
Orbital Energy ◽  
Molecular Orbital Energy ◽  
The One ◽  
Semi Empirical

Using the recently proposed reciprocal mean for the semi-empirical evaluation of resonance integrals, as well as approximate SCF wave functions for Co3+, the one-electron molecular energy levels of Co (NH3) 3+, Co (NH3) 5Cl2+, and Co (NH3) 4Cl21+ have been redetermined within the WOLFSBERG–HELMHOLZ approximation. The outcome of the study fits remarkably well with the observed electronic transitions in the u.v. spectra of these complexes and prompts different band assignments than previously suggested.

Vibrational analysis of the low resolution absorption spectra of BrClCS and Br2CS

1988 ◽  
Vol 66 (3) ◽  
pp. 359-366 ◽  
Author(s):  
B. Simard ◽  
R. P. Steer ◽  
R. H. Judge ◽  
D. C. Moule
Keyword(s):  
Absorption Spectra ◽  
Room Temperature ◽  
Vibrational Analysis ◽  
Vibrational Frequencies ◽  
Low Resolution ◽  
Barrier Heights ◽  
Vibrational Levels ◽  
Out Of Plane ◽  
The Given

The [Formula: see text] absorption spectra of BrClCS and Br2CS have been photographed under low resolution at room temperature. The electronic origins of BrClCS and Br2CS have been placed at 17116 and 16859 cm−1, respectively. Vibronic analyses show that the molecules are non-planar in their ā states. By fitting quadratic–Gaussian and quadratic–quartic double-minimum potentials to the observed vibrational levels of the out-of-plane manifolds, the equilibrium out-of-plane angles and the barrier heights to molecular inversion have been estimated to be 25 ± 1 deg and 541 ± 10 cm−1 for BrClCS, and 17.5 ± 1 deg and 524 ± 10 cm−1 for Br2CS. In the case of BrClCS, all six ā state vibrational frequencies have been obtained. In the case of Br2CS, only modes 1 (C—S stretch), 2 (symmetric C—Br stretch), 3 (in-plane Br—C—Br scissor), and 4 (out-of-plane bend) are active in the spectrum. Comparisons with other tetraatomic thiocarbonyls support the given assignments.

Group vibrations and the vibrational analysis of molecules containing methylene groups. Part II. Ethylene oxide, d4-ethylene oxide, and ethylene sulfide

1968 ◽  
Vol 46 (12) ◽  
pp. 2135-2139 ◽  
Author(s):  
J. M. Freeman ◽  
T. Henshall
Keyword(s):  
Ethylene Oxide ◽  
Vibrational Analysis ◽  
Vibrational Assignments ◽  
Group Frequency ◽  
Methylene Groups

Vibrational analyses, based on the group frequency factorization procedure of King and Crawford, are reported for ethylene oxide, d4-ethylene oxide, and ethylene sulfide in an attempt to decide between two possible vibrational assignments for these molecules.The results, whilst not providing an unequivocal decision between the assignments, nevertheless do suggest that the higher frequencies in the A2 and B2 species may be preferentially assigned to the methylene rocking modes.

Vibrational Assignments of Organosilanetriols. II. Crystalline Phenylsilanetriol and Phenylsilanetriol-D3

1978 ◽  
Vol 32 (5) ◽  
pp. 469-479 ◽  
Author(s):  
H. Ishida ◽  
J. L. Koenig
Keyword(s):  
Fourier Transform ◽  
Raman Spectra ◽  
Vibrational Modes ◽  
Torsional Mode ◽  
Vibrational Assignments ◽  
Laser Raman ◽  
Sioh Group ◽  
Laser Raman Spectra ◽  
Out Of Plane ◽  
Bending Modes

Fourier transform infrared spectra (3800 to 450 cm−1) and laser Raman spectra (4000 to 0 cm−1) of crystalline phenylsilanetriol and phenylsilanetriol-d3, and liquid state phenylsilanetriol and phenylsilanetriol-d3 are first reported. Complete band assignments are attempted. All vibrational modes of the SiOH group except for the SiC torsional mode, including the SiOH in-plane and out-of-plane bending modes, are observed. In addition to the phenylsilanetriols, infrared and laser Raman spectra of crystalline diphenylsilanediol and triphenylsilanol are also studied to aid the band assignments.

The visible absorption spectrum of 1,2-cyclobutanedione in the gas phase

1986 ◽  
Vol 64 (11) ◽  
pp. 2152-2161 ◽  
Author(s):  
R. A. Back ◽  
J. M. Parsons
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Singlet State ◽  
Energy Levels ◽  
Vibrational Structure ◽  
Visible Absorption Spectrum ◽  
Excited Singlet ◽  
Bending Vibration ◽  
Visible Absorption ◽  
Out Of Plane

The visible absorption spectrum of 1,2-cyclobutanedione has been measured in the gas phase at wavelengths between 4000 and 5100 Å. The absorption is attributed to the allowed π* ← n+, 1B1 ← 1A1 transition corresponding to the first excited singlet state. The spectrum shows a complex well-resolved vibrational structure which has been analysed, with some 125 bands measured and assigned. The bands at the longer wavelengths show sharp rotational fine structure, not yet analysed. The strongest band in the spectrum at 4933 Å has been assigned as the 0–0 band, while a band almost as strong at 4820 Å is attributed to excitation of one quantum of [Formula: see text], the a2 out-of-plane carbonyl bending vibration, and it is suggested that this band owes its intensity to vibronic coupling. A number of symmetric vibrations are also excited in the spectrum, but with no long progressions. Sequence bands running to the blue with an interval of about 72 cm−1 are prominent throughout the spectrum, and are assigned to v13, the a2 ring-twisting vibration. Other hot bands were also observed involving v13 which permitted estimation of energy levels for this vibration both in the ground state and the excited state. The infrared spectrum was also measured and analysed in the gas phase between 600 and 4000 cm−1, and 14 bands were assigned to fundamental vibrations; some of these assignments, at the lower frequencies, are uncertain.

Colour centres in irradiated diamonds. I

1957 ◽  
Vol 241 (1227) ◽  
pp. 433-454 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Structure ◽  
Theoretical Calculation ◽  
Energy Levels ◽  
Electronic Transitions ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Colour Centres ◽  
Quantitative Results ◽  
Isolated Neutral

A theoretical calculation of the energy levels, and hence absorption spectrum, of an isolated vacancy in an otherwise perfect diamond lattice has been made. The concept of a defect molecule is introduced. This enables familiar molecular orbital theory to be applied in calculating the electronic structure of the defect. The quantitative results suggest that the observed band at 2·0 eV causing irradiated diamonds to appear blue, is due to spin and orbitally allowed electronic transitions of symmetry 1 E → 1 T 2 in the neighbourhood of isolated neutral vacancies.

An internal coordinate model for molecular vibrations: the energy levels of H2O and H2S and related isotopic molecules

1978 ◽  
Vol 56 (16) ◽  
pp. 2167-2172 ◽  
Author(s):  
Jan Bron ◽  
R. Wallace
Keyword(s):  
Potential Function ◽  
Energy Levels ◽  
Vibrational Analysis ◽  
Polyatomic Molecules ◽  
Bending Vibration ◽  
Relative Simplicity ◽  
Anharmonic Vibrations ◽  
Vibrational Excitations ◽  
Coordinate Model ◽  
Good Agreement

Refinement of a previously described model for describing the anharmonic vibrations of polyatomic molecules is presented. The nonlinear molecules XY2 (H2O, D2O, H2S, D2S) are used as examples and it is shown that quite good agreement with the observed spectrum can be obtained for the first twenty vibrational excitations with a six parameter potential function. Apart from its relative simplicity, the main improvement over previously reported work is the inclusion of the bending vibration within the formalism and refinement of the form of potential. It is pointed out that the model is readily extendable to the vibrational analysis of larger molecules.

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