کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
7846588 1508765 2018 10 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Providing theoretical data for detection of four formamidic acid isomers in astrophysical media
ترجمه فارسی عنوان
ارائه داده های نظری برای تشخیص 4 ایزومر اسید فرمامیدیک در رسانه های استروفی فیزیکی
کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه شیمی طیف سنجی
چکیده انگلیسی
We present a theoretical study, so that molecular data (geometrical parameters, vibrational frequencies, infrared intensities, electronic energies, enthalpies, and Gibbs energies) of four formamidic acid (FA) isomers (labeled here as FA1, FA2, FA3, and FA4) and formamide (HCONH2) are obtained from CCSD/cc-pVTZ, CCSD/aug-cc-pVTZ, CCSD/cc-pVQZ, and CCSD(T)/cc-pVTZ calculations. Furthermore, on the basis of insufficient or even lacking theoretical and experimental results in the literature, we employed the aforementioned theory levels to determine benchmark values of dipole moments and rotational constants for these four FA isomers in order to contribute for their detection in astrophysical environments. Besides, we provide for the first time data about forward and reverse rate constants (200-4000 K) and Arrhenius' parameters for each interconversion reaction between pairs of FA isomers as well as for the tautomeric process involving FA4 and formamide, which were calculated from a Complete Basis Set (CBS) extrapolation equation obtained at CCSD/cc-pVTZ optimized geometries. Our kinetic analysis indicated a faster interconversion between the FA structures in comparison with the FA4 ↔ HCONH2 process, suggesting that these isomers could co-exist in astrophysical media. Finally, we estimated that these isomers may be detected with relative abundances, [FAx]/[HCONH2] (x = 1, 2, 3, and 4), between ∼0.01 and ∼0.1% in astrophysical sources at chemical equilibrium conditions and temperatures around 1000 K. However, these ratios can become as high as ∼1, ∼3, and ∼5%, respectively, in hotter regions with temperatures around 2000, 3000, and 4000 K (expected, for example, in massive star-forming regions).
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Molecular Astrophysics - Volume 10, March 2018, Pages 1-10
نویسندگان
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