The Missing Link of Sulfur Chemistry in TMC-1: The Detection of c-C3H2S from the GOTHAM Survey

Abstract

We present the spectroscopic characterization of cyclopropenethione in the laboratory and detect it in space using the Green Bank Telescope Observations of TMC-1: Hunting Aromatic Molecules survey. The detection of this molecule—the missing link in understanding the C _3 H _2 S isomeric family in TMC-1—completes the detection of all three low-energy isomers of C _3 H _2 S, as both CH _2 CCS and HCCCHS have been previously detected in this source. The total column density of this molecule ( N _T of $5.7{2}_{-1.61}^{+2.65}\times 1{0}^{10}$ cm ^−2 at an excitation temperature of $4.{7}_{-1.1}^{+1.3}$ K) is smaller than both CH _2 CCS and HCCCHS and follows nicely the relative dipole principle (RDP), a kinetic rule of thumb for predicting isomer abundances that suggests that, all other chemistry among a family of isomers being the same, the member with the smallest dipole ( μ ) should be the most abundant. The RDP now holds for the astronomical abundance ratios of both the S-bearing and O-bearing counterparts observed in TMC-1; however, CH _2 CCO continues to elude detection in any astronomical source.

Keywords

• Astrochemistry
• Chemical abundances