Torsional vibrations in jet-cooled acetaldehyde

Hong-bing, GU; Kundu, Tapanendu; Goodman, Lionel

doi:10.1021/j100130a012

Cited by 27 publications

(15 citation statements)

References 4 publications

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“…25 The calculation of a formyl torsion distortion in S 1 propanal is consistent with the S 1 state of acetaldehyde which adopts a pyramidal carbonyl atom with the O atom staggered with respect to the H atoms on the methyl group. 19,20,[39][40][41][42][43][44][45][46][47][48][49] Similar conclusions have been made for the acetaldehyde T 1 state. [45][46][47]50,51 These results for acetaldehyde have been corroborated with ab initio calculations on both the S 1 and T 1 Fig.…”

Section: The Formyl Torsionsupporting

confidence: 56%

“…This has indeed been noted for acetaldehyde. 19,20,[39][40][41][42]48,49 Moreover, as has been found recently in acetaldehyde, there is strong coupling between these modes and overall rotation that significantly complicates the spectral assignment at rotational resolution. 19,20 In the case of propanal, the vibrational coupling will be further complicated for several reasons.…”

Section: The S 1 S 0 (N P*) Transitionmentioning

confidence: 94%

See 1 more Smart Citation

The lowest-lying excited singlet and triplet electronic states of propanal: an ab initio molecular orbital investigation of the potential energy surfaces

Buntine

Chan-Sik

Metha

2004

Phys. Chem. Chem. Phys.

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This study explores the potential energy surfaces of the S 0 , S 1 and T 1 states using ab initio theory to provide insight into the spectroscopy, photochemistry and reaction dynamics of propanal. Minima associated with the formyl potential energy coordinate in the S 1 and T 1 states are found to be $60 out-of-phase with the S 0 state. Furthermore, the excited states possess a pyramidal formyl carbon atom that leads to a double minimum at AE33 and AE49 for the S 1 and T 1 states, respectively. An exploration of the C-C dissociation coordinate on the T 1 surface, yielding the products CH 3 CH 2 þ CHO, shows that a three-fold potential due to the formyl torsion is still operational, resulting in three unique transition states that lead to dissociation. The lowest energy pathway to dissociation occurs at a barrier height of 4766 cm À1 and the energy of the products is found to be 1017 cm À1 , relative to the T 1 global minimum. Consequently, a reverse barrier of 3749 cm À1 is calculated. Parameters calculated for the lowest energy transition state geometry are distinctly different from structures inferred from experiment, which assumed an isotropic dissociation channel.

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Section: The Formyl Torsionsupporting

confidence: 56%

Section: The S 1 S 0 (N P*) Transitionmentioning

confidence: 94%

The lowest-lying excited singlet and triplet electronic states of propanal: an ab initio molecular orbital investigation of the potential energy surfaces

Buntine

Chan-Sik

Metha

2004

Phys. Chem. Chem. Phys.

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“…[3][4][5] The Rydberg experiment reveals the historically missing a 2 torsional fundamental and its overtone in acetone, for example. 3 In addition, since electron distributions in the Rydberg states approach those for the corresponding radical cations, which are very different from the ground state, new insight into torsional barrier origins can be obtained by comparison of potential energy surfaces hindering internal rotation in the ground state with the Rydberg ones.…”

Section: Introductionmentioning

confidence: 99%

Getting the Shape of Methyl Internal Rotation Potential Surfaces Right

1996

Self Cite

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The effect of the multidimensional character of methyl internal rotation on torsional potential functions in small conjugated methyl molecules is discussed. Partitioned energetics obtained from different ab initio calculation levels are divided into σ and π symmetry components and then further dissected by breakdown of the fully relaxed internal rotation process into separate relaxation steps and their nuclear virials. Important contributions to barrier shape, height, and origin are thus disclosed. The analysis reveals closely balanced antagonistic π and σ contributions as determinants for the barrier height and identifies the dominant contributions to the barrier origin as σ-bonding changes largely resulting from bond lengthening during methyl group rotation. Skeletal hydrogen out-of-plane motion components of the torsional coordinate (e.g. CH 2 ethylenic twisting in propene) provide a general mechanism for barrier narrowing in small conjugated methyl molecules. Rydberg jet experiments are discussed as a general means for obtaining accurate torsional frequency information (including ground state) to test internal rotation potential surface models.

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“…The REMPI processes employed in this work involve a two-photon resonant 3s +-n Rydberg transition of acetaldehyde followed by one-photon ionization [15,20,21,[27][28][29][30][31]. The (2 + l) REMPI spectra of acetaldehyde first was reported in the wavelength range 368-358 nm by Heath et al [27], who used a parallel-plate ionization cell.…”

mentioning

confidence: 99%

“…Fisanick et al [15] reported both MPI mass spectra and mass-selected REMPI spectra by using a quadrupole mass filter. Goodman and co-workers [30] studied torsional vibronic bands by using a parallel plate detector. Recently, the mass-selected REMPI spectra were recorded by Buntine et al [21] for several deuterated acetaldehydes for the differentiation of possible sym and asym rotamers of the methyl group by utilizing a TOF detection system.…”

mentioning

confidence: 99%

Fourier transform ion cyclotron resonance detection of multiphoton ionization spectroscopy

Shin

Han

Kim

1996

J. Am. Soc. Mass Spectrom.

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Fourier transform ion cyclotron resonance (FT-ICR) detection was tested for resonanceenhanced multiphoton ionization (REMPI) spectroscopy. The (2+1) REMPI spectra of acetaldehyde were obtained in the wavelength range 364-354 nm via a two-photon resonant 3s ← n Rydberg transition. The space-charge effects on the REMPI spectra were examined in the vicinity of the 0 0 (0) transition. The trapping efficiency measurement shows that all the ions produced from REMPI dissociation processes are arrested in the ion cyclotron resonance cell even in the presence of space-charge interactions. Axial kinetic energy release distributions of ions were extracted from the trapping efficiency data obtained under a new space-charge-free condition. FT-ICR peak heights were measured as a function of pressure at different laser powers, magnetic field strengths, and ion excitation methods to test for the detection linearity. The FT-ICR detection responds linearly to the number of ions in a low pressure limit. The product branching ratio was measured by using various ion excitation methods and was compared with the previous quadrupole mass spectrometric study. FT-ICR detection yields the mass-selected REMPI spectra and the product branching ratio in the absence of kinetic shifts.

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Torsional vibrations in jet-cooled acetaldehyde

Cited by 27 publications

References 4 publications

The lowest-lying excited singlet and triplet electronic states of propanal: an ab initio molecular orbital investigation of the potential energy surfaces

The lowest-lying excited singlet and triplet electronic states of propanal: an ab initio molecular orbital investigation of the potential energy surfaces

Getting the Shape of Methyl Internal Rotation Potential Surfaces Right

Fourier transform ion cyclotron resonance detection of multiphoton ionization spectroscopy

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