VIBRATIONALLY EXCITED c-C3H2 RE-VISITED: NEW LABORATORY MEASUREMENTS AND THEORETICAL CALCULATIONS

Abstract

Cyclopropenylidene, $c$-C$_3$H$_2$, is one of the more abundant organic molecules in the interstellar medium, as evidenced from astronomical detection of its single $^{13}$C and both its singly- and doubly-deuterated isotopic species. For this reason, vibrational satellites are of considerable astronomical interest, and were the primary motivation for the earlier laboratory work by Mollaaghababa and co-workers [1].\_x000d_ indent The recent detection of intense unidentified lines near 18,GHz in a hydrocarbon discharge by FT microwave spectroscopy has spurred a renewed search for the vibrational satellite transitions of $c$-C$_3$H$_2$. Several strong lines have been definitively assigned to the $v_6$ progression on the basis of follow-up measurements at 3,mm, double resonance and millimeter-wave absorption spectroscopy, and new theoretical calculations using a rovibrational VMP2 method [2] and a high-quality ab initio potential energy surface. The treatment was applied to several excited states as well as the ground state, and included deperturbation of Coriolis interactions._x000d_ _x000d_ [1] R. Mollaaghababa, C.A. Gottlieb, J. M. Vrtilek, and P. Thaddeus, textit{J. Chem. Phys.}, textbf{99}, 890-896 (1992)._x000d_ _x000d_ [2] P.~B. Changala and J.~H. Baraban. textit{J. Chem. Phys.}, textbf{145}, 174106 (2016)._x000d_ _x000d_