Suggestion for search of ethylene oxide ($c$-C₂H₄O) in a cosmic object

Abstract

Ethylene oxide ($c$-C₂H₄O) and its isomer acetaldehyde (CH₃CHO) are important organic molecules because of their potential role in the formation of amino acids. The $c$-C₂H₄O molecule is a $b$-type asymmetric top molecule and owing to half-spin of each of the four hydrogen atoms, it has two distinct ortho (nuclear spin one) and para (nuclear spin zero and two) species. It has been detected in the Sgr B2N. Using the rotational and centrifugal distortion constants along with the electric dipole moment, we have calculated energies of 100 rotational levels of each of the ortho and para species of $c$-C₂H₄O molecule and the Einstein $A$-coefficients for radiative transitions between the levels. The values of Einstein $A$-coefficients along with the scaled values for the collisional rate coefficients are used for solving a set of statistical equilibrium equations coupled with the equations of radiative transfer.

Brightness-temperatures of five rotational transitions of each of the ortho and para species of $c$-C₂H₄O molecule are investigated. Out of these ten transitions, three transitions are found to show the anomalous absorption and rest seven are found to show the emission feature. We have also investigated seven transitions observed unblended in the Sgr B2(N). We have found that the transitions $3_{3 0} - 3_{2 1}$ (23.134 GHz), $2_{2 0} - 2_{1 1}$ (15.603 GHz), $3_{3 1} - 3_{2 2}$ (39.680 GHz) and $1_{1 1} - 0_{0 0}$ (39.582 GHz) may play important role for the identification of ethylene oxide in a cosmic object.