Providing theoretical data for detection of four formamidic acid isomers in astrophysical media

Autor(es)

Vichietti, R. M. ^[1] ; da Silva, A. B. F. ^[1] ; Haiduke, R. L. A. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, CP 780, BR-13560970 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: MOLECULAR ASTROPHYSICS; v. 10, p. 1-10, MAR 2018.
• Citações Web of Science: 1

Resumo

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/ccpVTZ, 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, {[}FA(x)]/{[}HCONH2] (x = 1, 2, 3, and 4), between similar to 0.01 and similar to 0.1% in astrophysical sources at chemical equilibrium conditions and temperatures around 10 0 0 K. However, these ratios can become as high as similar to 1, similar to 3, and similar to 5%, respectively, in hotter regions with temperatures around 20 0 0, 30 0 0, and 40 0 0 K (expected, for example, in massive star-forming regions). (C) 2018 Elsevier B.V. All rightsreserved. (AU)

• Processo FAPESP: 10/18743-1 - Uso de multipolos da teoria quântica de átomos em moléculas e estudos cinéticos em sistemas encontrados no meio interestelar
• Beneficiário: Roberto Luiz Andrade Haiduke
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/23714-1 - Cálculos relativísticos de estrutura eletrônica para avaliação de novos conjuntos de funções de base sem prolapso variacional
• Beneficiário: Roberto Luiz Andrade Haiduke
• Modalidade de apoio: Auxílio à Pesquisa - Regular