Update on the TEXES Titan Mid-Infrared Spectral Survey

At this meeting we will present the current status of the survey, including results on allene (CH2CCH2). We have tentatively identified several of the ∼10 subbands of allene amongst the strong emission lines of ethane's ∼12 822 cm-1 band. The observed spectrum of the ∼845 cm-1 subband are shown in Figure 1. Although often searched for, allene has not previously been detected in Titan's atmosphere. We discuss the challenges of identifying and measuring the abundance of allene when line lists and strengths are often in significant disagreement. In the case of allene a commonly used line list3 predicts significantly stronger emission for the same atmospheric abundance than what is predicted using absorption coefficient spectra empirically derived from cold laboratory spectroscopy. The lack of good line lists and/or high-resolution cold laboratory spectra is a significant obstacle to identifying the many as-yet-unidentified emission lines in the survey's spectra.