THE \lq{}4050 \AA GROUP\rq{} OF THE \ {A}$^{1}\Pi_{u}$ - \ {X}$^{1}\Sigma_{g}^{+}$ TRANSITION SYSTEM OF C$_{3}$
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Date
2013
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Publisher
Ohio State University
Abstract
The \lq{}4050~\AA ~group\rq{} of C$_{3}$, which consists of a series of bands of the \~{A}$^{1}\Pi_{u}$ - \~{X}$^{1}\Sigma_{g}^{+}$ electronic transition system, has been of much interest to astronomers as it serves as a remote diagnostic of the physical-chemical conditions in translucent interstellar clouds. In this contribution, we present: a) The high resolution ($R=80~000$) detection of eight vibronic bands of C$_{3}$ in the diffuse translucent cloud towards HD~169454. Four of these vibronic bands are also detected in two additional objects: HD~73882 and HD~154368. Column densities and excitation conditions of C$_{3}$ are inferred. b) A laboratory re-examination of the eight vibronic bands observed towards HD~169454 using cavity ring-down spectroscopy and a supersonic plasma jet. High-quality laboratory data build the list of lines with a wavelength accuracy of $\textless$0.01\AA. This is sufficient for the analysis of the observational data. Improved spectroscopic parameters of the corresponding vibronic states are presented. An improved perturbation analysis in the \~{A}$^{1}\Pi_{u}$ (000) state is given as well. c) The systematic laboratory investigation on the \~{A}$^{1}\Pi_{u}$ - \~{X}$^{1}\Sigma_{g}^{+}$ 000-000 electronic origin band of $^{13}$C-substituted C$_{3}$. Rotationally resolved spectra of all five $^{13}$C-isotopologues are recorded in a supersonic plasma expansion by discharging $^{13}$C$_{2}$H$_{2}$ or $^{12}$C$_{2}$H$_{2}$/$^{13}$C$_{2}$H$_{2}$ mixtures diluted in noble gas. The \~{A}$^{1}\Pi_{u}$ state molecular constants for all five isotopologues and ground-state molecular constants for $^{13}$C$^{12}$C$^{13}$C and $^{12}$C$^{13}$C$^{13}$C are experimentally determined for the first time. This work extends the recent mid-infrared work on the $^{13}$C-isotopologues of C$_{3}$ by Giesen \textit{et al.}
Description
Author Institution: Sackler Laboratory for Astrophysics, Leiden Observatory, University of Leiden, P.O. Box 9513, NL-2300 RA Leiden, the Netherlands; LaserLaB, VU University Amsterdam, De Boelelaan 1081, NL-1081 HV, Amsterdam, The Netherlands; Department of Astrophysics, N. Copernicus Astronomical Center; ul. Rabianska 8, 87-100 Torun, Poland; Centre for Astronomy, Nicolaus Copernicus University, Gagarina 11, 87-100 Torun, Poland; Instituto de Astronomia, Universidad Catolica del Norte, Av. Angamos 0610; Antofagasta, Chile