Spectroscopy of the Acetylenic CH Stretch of Propyne-d3 in the Region of the Second Overtone

Ganot, Yuval; Chen, X.; Bar, Ilana; Rosenwaks, Salman

doi:10.1006/jmsp.2001.8383

Cited by 11 publications

(5 citation statements)

References 25 publications

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“…The temperature was estimated from the simulation of the action spectrum obtained in the VMP of the second C-H overtone of propyne-d 3 , seeded in Ar under similar expansion conditions. 26,33 It is clearly seen that only a small number of rotational states should be populated at this low rotational temperature and therefore appear in the calculated and action spectra. However, the action spectrum related to transitions of the (1030 0 0 0 ) state includes additional lines, with intensities differing substantially from those in the calculated absorption spectrum, based on a Boltzmann distribution at 10 K. This implies that the enhancement of the observed lines in the photodissociation step varies significantly for different rovibrational lines, resulting in an anomalous intensity pattern of the (1030 0 0 0 ) band.…”

Section: A Photoacoustic Versus Action Spectramentioning

confidence: 94%

Disclosing rovibrational couplings and overlaps from irregularities in action spectra: Photodissociation of the 4νCH rovibrational manifold of C2H2

Sheng

Ganot

Rosenwaks

et al. 2002

The Journal of Chemical Physics

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Absorption and free-jet action spectroscopy of states in the region of four quanta of C-H stretching of acetylene (C 2 H 2 ) around 12 676 cm Ϫ1 were studied. Rovibrational excitation combined with 243.135 nm promotion of C 2 H 2 molecules to the upper electronic trans-bent states, Ã 1 A u /B 1 B u , and H photofragment ionization generated action spectra measuring the H yield as a function of the excitation wavelength. The findings show that the (1030 0 0 0 ) IR bright state of the third C-H stretch overtone has a smaller photodissociation cross section than the (1214 0 0 0 ) combination band containing trans-bend mode excitation and lying in its vicinity, due to a favorable Franck-Condon factor for the latter. Certain line pairs accessing similar JЈ levels of the (1030 0 0 0 ) state show anomalous intensities in the action spectrum, with P transitions excessively enhanced over R transitions. This implies enormous dissociation efficacy as a consequence of Coriolis-type local resonances with nearby states of another band and due to the overlap of the P transitions with another band.

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Section: A Photoacoustic Versus Action Spectramentioning

confidence: 94%

Disclosing rovibrational couplings and overlaps from irregularities in action spectra: Photodissociation of the 4νCH rovibrational manifold of C2H2

Sheng

Ganot

Rosenwaks

et al. 2002

The Journal of Chemical Physics

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“…[23][24][25][26][27] These results indicate that the acetylenic C-H stretch is a relatively long-lived mode that does not significantly interact in a resonant manner with any molecular fragment attached to the opposite end of the acetylenic C-H of the molecule.…”

Section: Discussionmentioning

confidence: 86%

Phase shift cavity ring down and Fourier transform infrared measurements of C–H vibrational transitions, energy levels, and intensities of (CH3)3Si–C≡C–H

Barroso

Perez-Delgado

Manzanares

2013

The Journal of Chemical Physics

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Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 1-5) and methyl (Δυ = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi≡CH] at 295 K. Harmonic frequencies ω(ν1), ω(a), and ω(s) and anharmonicities x(ν1), ω(a)x(a), ω(s)x(s) were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. A hot band, assigned as υν1 + ν24 - ν24 is observed for transitions with Δυ = 1-5 in a region near the acetylenic stretch. The intensity of the hot band is reduced considerably at 240 K. The strength of a Fermi resonance between C-Ha transition (υν(a)) and the combination band ((υ-1)ν(a) + 2ν(bend)) with (υ = 3-6) was calculated using the experimental perturbed energies and relative intensities. The main bands are separated by computer deconvolution and are integrated at each level to get the experimental band strengths. For methyl absorptions, the dipole moment function is expanded as a function of two C-H stretching coordinates and the intensities are calculated in terms of the HCAO model where only the C-H modes are considered. Acetylenic intensities are derived with a one dimensional dipole moment function. The expansion coefficients are obtained from molecular orbital calculations. The intensities are calculated without using adjustable parameters and they are of the same order of magnitude of the experimental intensities for all C-H transitions.

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“…The conjecture that the N state is brighter in UV excitation is supported by the simulation results of the PA and action spectra [17] in the 3 1 region (Figure 7(A) panels (b) and (d), respectively) obtained by the code described in [40]. Briefly, the propyne bands match A 1 symmetry and undergo parallel transitions, following the DJ ¼ 0, AE1 and DK ¼ 0 selection rules.…”

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confidence: 94%

“…The intensity of the H spectrum (panel c) was found to be lower than that of D (panel b) and therefore it was scaled up for the sake of presentation. The fitted rovibrational parameters for the bands in the 3 1 and 4 1 regions of propyne-d 3 were obtained using a symmetric rotor program [40]. Comparison of the fitted action spectra (solid lines) to the measured ones (points) of Figures 8 and 9 (panels b and c) and of the substantial parts of the fitted (solid lines) and measured (points) PA spectra (Figures 8 and 9 (panel a)), which include J values up to 40, shows that the fitting reproduces well the measured spectra.…”

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confidence: 99%

Vibrationally mediated photodissociation of ethyne isotopologues and homologues revisited

Bar

Rosenwaks

2012

Molecular Physics

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The extensive studies on photodissociation of rovibrationally pre-excited ethyne isotopologues and homologues are reviewed. These studies are utilized here for comparing the dynamics of energy flow in C 2 H 2 and C 2 HD to that in H 3 CCCH, D 3 CCCH and H 3 CH 2 CCCH. Evidence on the intramolecular dynamics comes from the extent of mode-and bond-selectivity in ethyne and its mono-deuterated variant and from the spectral linewidth in propyne and butyne. In the smaller species, rotational and vibrational mode-and bond-selective cleavage were observed, while in the larger ones mode-dependent lifetimes were found. The different behaviour of the two groups with regard to preferential bond-fission indicates that in the former the intramolecular vibrational distribution lifetime is on the ns timescale, whereas in the latter it is at least one order of magnitude shorter. These observations are interpreted following the recent progress in the understanding of the intramolecular dynamics of these species.

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Spectroscopy of the Acetylenic CH Stretch of Propyne-d3 in the Region of the Second Overtone

Cited by 11 publications

References 25 publications

Disclosing rovibrational couplings and overlaps from irregularities in action spectra: Photodissociation of the 4νCH rovibrational manifold of C2H2

Disclosing rovibrational couplings and overlaps from irregularities in action spectra: Photodissociation of the 4νCH rovibrational manifold of C2H2

Phase shift cavity ring down and Fourier transform infrared measurements of C–H vibrational transitions, energy levels, and intensities of (CH3)3Si–C≡C–H

Vibrationally mediated photodissociation of ethyne isotopologues and homologues revisited

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