SPIN-FORBIDDEN AND SPIN-ALLOWED CYCLOPROPENONE (c-H 2 C 3 O) FORMATION IN INTERSTELLAR MEDIUM

Three proposed mechanisms of cyclopropenone (c-H{sub 2}C{sub 3}O) formation from neutral species are studied using high-level electronic structure methods in combination with nonadiabatic transition state and collision theories to deduce the likelihood of each reaction mechanism under interstellar c...

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Vydáno v:The Astrophysical journal Ročník 795; číslo 2; s. 173
Hlavní autoři: Ahmadvand, Seyedsaeid, Zaari, Ryan R., Varganov, Sergey A.
Médium: Journal Article
Jazyk:angličtina
Vydáno: United States 10.11.2014
Témata:
ACETYLENE
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
CARBON MONOXIDE
COLLISIONS
DIFFUSION BARRIERS
INTERSTELLAR SPACE
MOLECULES
OXYGEN
PROBABILITY
SPACE
SPIN
STARS
ISSN:1538-4357, 0004-637X, 1538-4357
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Shrnutí:Three proposed mechanisms of cyclopropenone (c-H{sub 2}C{sub 3}O) formation from neutral species are studied using high-level electronic structure methods in combination with nonadiabatic transition state and collision theories to deduce the likelihood of each reaction mechanism under interstellar conditions. The spin-forbidden reaction involving the singlet electronic state of cyclopenylidene (c-C{sub 3}H{sub 2}) and the triplet state of atomic oxygen is studied using nonadiabatic transition state theory to predict the rate constant for c-H{sub 2}C{sub 3}O formation. The spin-allowed reactions of c-C{sub 3}H{sub 2} with molecular oxygen and acetylene with carbon monoxide were also investigated. The reaction involving the ground electronic states of acetylene and carbon monoxide has a very large reaction barrier and is unlikely to contribute to c-H{sub 2}C{sub 3}O formation in interstellar medium. The spin-forbidden reaction of c-C{sub 3}H{sub 2} with atomic oxygen, despite the high probability of nonadiabatic transition between the triplet and singlet states, was found to have a very small rate constant due to the presence of a small (3.8 kcal mol{sup –1}) reaction barrier. In contrast, the spin-allowed reaction between c-C{sub 3}H{sub 2} and molecular oxygen is found to be barrierless, and therefore can be an important path to the formation of c-H{sub 2}C{sub 3}O molecule in interstellar environment.
ISSN:1538-4357
0004-637X
1538-4357
DOI:10.1088/0004-637X/795/2/173