A re-examination of the 4051 إ band of C3 using cavity ringdown spectroscopy of a supersonic plasma

The C3 molecule is of fundamental interest to chemists, both as the simplest cumulene and as a prototypical nonrigid system. It is also of great importance in astrophysics, as it now serves as a remote diagnostic of the temperature and density of interstellar clouds. However, high resolution astronomical spectra have uncovered a discrepancy between the observed R(0) transition and the laboratory spectrum. We have used cavity ringdown spectroscopy to obtain a high resolution, low temperature spectrum of the 4051 إ band, and have confirmed that the R(0) transition was incorrectly assigned in previous laboratory work.