M. Fatima, H. S. P. Müller, O. Zingsheim, F. Lewen, V. M. Rivilla, I. Jiménez-Serra, J. Martín-Pintado, and S. Schlemmer
reported on the
Millimetre and Submillimetre Spectroscopy of Isobutene and Its Detection in the Molecular Cloud G+0.693
Astron. Astrophys. 680, Art. No. A25 (2023).
Isobutene, (CH₃)₂C=CH₂, is one of four non-cyclic C₄H₈ isomers; another isomer is cyclobutane. It was identified in the course of a molecular line survey of the Galactic center cold molecular cloud G+0.693−0.027 carried out with the Yebes 40 m and IRAM 30 m radio telescopes. Six b-type lines with 3 ≤ J ≤ 10, K_c between J and J − 2, and with unresolved internal rotation splitting were not or only slightly blended and show reasonable signal-to-noise ratios. The authors also identify propene in this source. Both molecules have excitation temperatures of about 15 K, and propene has an about three times higher column density than isobutene. Isobutene is only the second molecules with a branched carbon chain after isopropyl cyanide.

Contributor(s): H. S. P. Müller; 12, 2023