Photochemistry of acetylene

Okabe, H.

doi:10.1139/v83-153

Cited by 38 publications

(19 citation statements)

References 14 publications

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“…It is well known [8,9] that ultraviolet laser photolysis of acetylene produces diacetylene. We have gen-erated small quantities of a number of isotopomers of diacetylene, using laser photolysis of suitable acetylene isotopomers.…”

Section: Methodsmentioning

confidence: 99%

Determination of the molecular structure of diacetylene from high-resolution FTIR spectroscopy

et al. 1995

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The high-resolution infrared absorption spectra of eight 2H or 13C substituted isotopomers of diacetylene have been recorded, and the bands corresponding to the ~' 4 fundamental and 2~,6 combination of the major isotopomer have been analyzed using a Loomis-Wood-type program. Effective ground-state rotational constants have been obtained from ground-state combination differences. A number of r 0, r., r~,, and (r~,)co~r structures have been calculated from the available data and are compared to those obtained by ab initio methods. The (r~,)r structure, which is a reliable near-equilibrium structure of diacetylene, is rc_ H = 106.131 (13)

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Section: Methodsmentioning

confidence: 99%

Determination of the molecular structure of diacetylene from high-resolution FTIR spectroscopy

et al. 1995

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“…A strong absorption line of C 2 H 2 coincides very nearly with the hydrogen Lyman-α line. The longest C 2 H 2 photodissociation threshold, forming C 2 H + H, occurs at 217 nm and the dissociation efficiency at shorter wavelengths was studied several times (e.g., Okabe 1983;Seki & Okabe 1993;Läuter et al 2002;Kovács et al 2010), as well as the probability of forming an H 2 product. Läuter et al (2002) convincingly determined a 100% efficiency for H-atom formation by 121.6 and 193.3 nm radiation after detecting these atoms through laser-induced fluorescence, and a 100% dissociation efficiency was assumed for all wavelengths shorter than the 217 nm threshold.…”

Section: H 2 -Acetylenementioning

confidence: 99%

Photodissociation and photoionisation of atoms and molecules of astrophysical interest

Heays

Bosman

Dishoeck

2017

A&A

425

442

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A new collection of photodissociation and photoionisation cross sections for 102 atoms and molecules of astrochemical interest has been assembled, along with a brief review of the basic physical processes involved. These have been used to calculate dissociation and ionisation rates, with uncertainties, in a standard ultraviolet interstellar radiation field (ISRF) and for other wavelength-dependent radiation fields, including cool stellar and solar radiation, Lyman-α dominated radiation, and a cosmic-ray induced ultraviolet flux. The new ISRF rates generally agree within 30% with our previous compilations, with a few notable exceptions. Comparison with other databases such as PHIDRATES is made. The reduction of rates in shielded regions was calculated as a function of dust, molecular and atomic hydrogen, atomic C, and self-shielding column densities. The relative importance of these shielding types depends on the atom or molecule in question and the assumed dust optical properties. All of the new data are publicly available from the Leiden photodissociation and ionisation database. Sensitivity of the calculated rates to variation of temperature and isotope, and uncertainties in measured or calculated cross sections, are tested and discussed. Tests were conducted on the new rates with an interstellar-cloud chemical model, and find general agreement (within a factor of two) in abundances obtained with the previous iteration of the Leiden database assuming an ISRF, and order-of-magnitude variations assuming various kinds of stellar radiation. The newly parameterised dust-shielding factors makes a factor-of-two difference to many atomic and molecular abundances relative to parameters currently in the UDfA and KIDA astrochemical reaction databases. The newly-calculated cosmic-ray induced photodissociation and ionisation rates differ from current standard values up to a factor of 5. Under high temperature and cosmic-ray-flux conditions the new rates alter the equilibrium abundances of abundant dark cloud abundances by up to a factor of two. The partial cross sections for H 2 O and NH 3 photodissociation forming OH, O, NH 2 and NH are also evaluated and lead to radiation-field-dependent branching ratios.

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“…The 308 nm photon energy is insufficient for photodissociation of C 2 H 2 in a singlephoton process. 59 The carbon molar fraction in the films did not show significant dependence on the laser fluence, indicating that multiphoton photodissociation processes are insignificant as well. The remaining possible routes for C 2 H 2 decomposition in the system include (i) thermal decomposition at and near the target surface that is transiently heated by laser pulses, (ii) thermal decomposition in the ablation plume plasma, and (iii) decomposition by impact with energetic particles in the plume.…”

Section: Discussionmentioning

confidence: 92%