The influence of molecular vicinity (expressed in terms of dielectric constant) on the infrared spectra of embedded species in ices and solid matrices

Autor(es)

Pilling, S. ^[1] ; Bonfim, V. S. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Vale Paraiba, UNIVAP, Lab Astroguim & Astrobiol LASA, Av Shishima Hifumi 2911, Sao Jose Dos Campos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: RSC ADVANCES; v. 10, n. 9, p. 5328-5338, FEB 2 2020.
• Citações Web of Science: 0

Resumo

In this theoretical work we evaluate how the chemical environment influences some features presented in the infrared spectrum, such as band intensities and band location of embedded species in icy matrices. The calculations were performed employing the Polarized Continuum Model (PCM) approach with the second-order MOller-Plesset perturbation theory (MP2) level using the Gaussian 09 package. Here, we simulate the effects of molecular vicinity around embedded species in terms of the effects of the dielectric constant (epsilon) of the icy and solid samples. Gas phase calculation was also performed for comparison purpose. The investigated embedded single molecules were CO, CO2, CH4, NH3, SO2 HCOOH, CH3OH and also H2O. The results suggest that for most vibrational modes, the strengths of IR bands show an increase with epsilon, which implies they also decrease with respect to porosity. The frequency shifts showed opposite behavior in relation to the band strengths, with few exceptions. A correlation between calculated band intensities with the band strengths A (taken from literature) was determined and described by a linear function I similar to 6 x 10(18)A {[}km mol(-1)], with A in unity of cm per molecule. In addition, an associative exponential function was adjusted to the studied dataset to characterize the evolution of frequency-shift and intensity-shift and band strength ratio as function of the dielectric constant. Since astrophysical ice mantles over cold dust grains can vastly vary in composition in space (having different dielectric constants) they are a challenge to be well characterized. Therefore, this work can help the astrochemistry community to better understand astrophysical ices and its observations in the infrared. (AU)

• Processo FAPESP: 09/18304-0 - Síntese e degradação de espécies moleculares pré-bióticas em atmosferas planetárias, cometas e gelos interestelares simulados
• Beneficiário: Sergio Pilling Guapyassu de Oliveira
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores