Revised infrared bending mode intensities for diacetylene (C4H2): Application to Titan

Diacetylene (C4H2) has been observed in various astrophysical environments in the infrared range through the bending modes ν8 at 628.0 and ν9 at 220.1 cm−1. Accurate intensity measurements of both modes are necessary to obtain precise abundance determination. Laboratory spectra covering both bending modes have been recorded with a pure diacetylene sample. Precise band intensities have been measured showing large discrepancies compared to previous studies, reaching a factor 2.3 for the ν9 band and a smaller difference of 20% for the ν8 band. Consequences on the determination of abundances of diacetylene in Titan׳s atmosphere are discussed.