Vibronic bands of the CCH radical observed by infrared diode laser kinetic spectroscopy

Kanamori, Hideto; Hirota, Eizi

doi:10.1063/1.454877

Cited by 75 publications

(49 citation statements)

References 14 publications

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“…Consequently, the activation barrier is higher than that of 3 C 2 þ C 2 H 6 , in which the TS resembles product-like, considering the relative energies of the reactants and products [29]. The vibrational frequencies of all the reactants, TS, and products at the BB1K/6-311þG(2d,2p) level are also in good agreement with available experimental results [37][38][39]. The TS possesses one and only one imaginary frequency i1151 cm…”

Section: Stationary Points and Reaction Mechanismsupporting

confidence: 71%

Direct ab initio dynamics study of the reaction of C₂(A³Π_u) with CH₄

Huo

Huang

et al. 2011

Int J of Quantum Chemistry

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The reaction of C 2 (A 3 P u ) with CH 4 has been investigated over a wide temperature range 200-3,000 K by direct ab initio dynamics method at the BMC-CCSD//BB1K/6-311þG(2d,2p) level of theory. The optimized geometries and frequencies of the stationary points are calculated at the BB1K/6-311þG(2d,2p) level, and then the energy profiles of the reactions are refined using the BMC-CCSD method. The activation barrier height for H-abstraction reaction was calculated to be 4.44 kcal/mol in temperature range (337-605 K), and the electron transfer behavior was also analyzed by quasi-restricted molecular orbital method in detail. The canonical variational transition-state theory (CVT) with the small curvature tunneling (SCT) correction method is used to calculate the rate constants over a wide temperature range 200-3,000 K. The theoretical results shows that variational effect is to some extent large in lower temperature range, and small curvature and tunneling effect play important roles to the H-atom abstraction only at lower temperatures. The CVT/SCT rate constants are in good agreement with the available experimental results. Our theoretical study is expected to provide a direct insight into the reaction mechanism and may be useful for estimating the kinetics of the title reaction over a wide temperature range where no experimental data are available so far.

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Section: Stationary Points and Reaction Mechanismsupporting

confidence: 71%

Direct ab initio dynamics study of the reaction of C₂(A³Π_u) with CH₄

Huo

Huang

et al. 2011

Int J of Quantum Chemistry

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“…This suggests that close to W 3(H 2 O), either the dust must be very hot or the conditions quite extreme (see also Helmich et al 1996). CCH has its lowest vibrational level at 370 cm −1 or 27 µm (Hsu et al 1993;Kanamori & Hirota 1988). At these wavelengths the infrared radiation is intense enough to pump this vibrational level.…”

Section: Vibrationally Excited Moleculesmentioning

confidence: 99%

Physical and chemical variations within the W3 star-forming region

Helmich

Jansen

Graauw³

et al. 1995

Lecture Notes in Physics

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Abstract. Results are presented of the 345 GHz spectral survey toward three sources in the W 3 Giant Molecular Cloud: W 3 IRS4, W 3 IRS5 and W 3(H 2 O). Nearly 90% of the atmospheric window between 334 and 365 GHz has been scanned using the James Clerk Maxwell Telescope (JCMT 1 ) down to a noise level of ∼ 80 mK per resolution element. These observations are complemented by a large amount of data in the 230 GHz atmospheric window. From this data set physical conditions and beam-averaged column densities are derived for more than 14 chemically different species (over 24 different isotopes). The physical parameters derived in Paper I (Helmich et al. 1994) are confirmed by the analysis of the excitation of other species, although there is evidence that the silicon-and sulfurbearing molecules exist in a somewhat denser and warmer environment. The densities are high, ≥ 10 6 cm −3 , in the three sources and the kinetic temperatures for the bulk of the gas range from 55 K for IRS4 to 220 K for W 3(H 2 O). The chemical differences between the three sources are very striking: silicon-and sulfur-bearing molecules such as SiO and SO 2 are prominent toward IRS5, whereas organic molecules like CH 3 OH, CH 3 OCH 3 and CH 3 OCHO are at least an order of magnitude more abundant toward W 3(H 2 O). Vibrationally excited molecules are also detected toward this source. Only simple molecules are found toward IRS4. The data provide constraints on the amount of deuterium fractionation and the ionization fraction in the observed regions as well. These chemical character- istics are discussed in the context of an evolutionary sequence, in which IRS5 is the youngest, W 3(H 2 O) somewhat older and IRS4, although still enigmatic, the oldest.

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“…Also, the secondary dissociation probability might have a gradual dependence on the primary product internal energy rather than the step function we are assuming. The secondary peEr) that best fit the spectra are bimodal (see Figure 10) If the former were true, they estimated an <a>eXe = 10.1 cm-' and if the latter were true, <a>eXe = -15.8 cm-' [40]. using these anharmonic constants, we predicted the values for other bending overtones.…”

Section: No-skimmer/low Resolutionmentioning

confidence: 99%

193 nm photodissociation of acetylene

Balko¹,

Zhang²,

Lee³

1991

The Journal of Chemical Physics

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The product translational energy distribution P(ET) for acetylene photodissociation at 193 nm was obtained from the time-of-flight spectrum of the H atom fragments. The P(ET) shows resolved structure from the vibrational and electronic excitation of the C2H fragment; comparison of the translational energy release for given excited states of C2H with the known energy levels of these states gives D0(HCC–H)=131.4±0.5 kcal/mol. This value is in agreement with that determined previously in this group from analogous studies of the C2H fragment and with the latest experimental and theoretical work. The high resolution of the experiment also reveals the nature of C2H internal excitation. A significant fraction of the H atoms detected at moderate laser power were from the secondary dissociation of C2H. The P(ET) derived for this channel indicates that most of the C2 is produced in excited electronic states.

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Vibronic bands of the CCH radical observed by infrared diode laser kinetic spectroscopy

Cited by 75 publications

References 14 publications

Direct ab initio dynamics study of the reaction of C₂(A³Π_u) with CH₄

Direct ab initio dynamics study of the reaction of C₂(A³Π_u) with CH₄

Physical and chemical variations within the W3 star-forming region

193 nm photodissociation of acetylene

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Vibronic bands of the CCH radical observed by infrared diode laser kinetic spectroscopy

Cited by 75 publications

References 14 publications

Direct ab initio dynamics study of the reaction of C2(A3Πu) with CH4

Direct ab initio dynamics study of the reaction of C2(A3Πu) with CH4

Physical and chemical variations within the W3 star-forming region

193 nm photodissociation of acetylene

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Direct ab initio dynamics study of the reaction of C₂(A³Π_u) with CH₄

Direct ab initio dynamics study of the reaction of C₂(A³Π_u) with CH₄