Suggestion for a Search of Diisocyanomethane (CNCH2NC) in the Cosmic Objects: Potential Spectral Lines

Abstract

Finding several molecules having cyanide group (-C≡N) and isocyanide group (-N≡C), scientists searching for life in the universe, are interested in the molecules having two cyanide or isocyanide groups. Diisocyanomethane (CNCH₂NC) having two isocyano groups is an interesting candidate for the astronomers, though it has not been detected in any cosmic object. However, three organic isocyanides (HNC, CH₃NC, HCCNC) have been found in the interstellar medium (ISM). Submillimeter wave spectrum of CNCH₂NC is analyzed by spectroscopists, so that it could be searched in the ISM. For searching CNCH₂NC in a cosmic object, information about its strong spectral lines is essentially required. For that, in our investigation, the rotational levels of CNCH₂NC can be classified into two species. The energies of lower 250 rotational levels up to 108 cm⁻¹, in the ground vibrational state, and the radiative transition probabilities for rotational transitions in each species are calculated, using the values of rotational and centrifugal distortion constants along with the electric dipole moment. A set of statistical equilibrium equations coupled with the equations of radiative transfer is solved by using the radiative transition probabilities and the scaled values of collisional rate coefficients as input data. For each species, we have found two transitions showing emission feature and four transitions showing anomalous absorption. These 12 transitions may help in the detection of CNCH₂NC in a cosmic object.