FTIR and diode laser spectroscopy of isobutylene: Analysis of the rotational structure in the v28 fundamental band

►FTIR and Pb-salt diode laser study of isobutylene at room temperature. ► Rotational structure in the 2801 band observed at 0.125 cm−1 spectral resolution. ► Spacing very regular in the P and R branches (Δv ≈ 0.6 cm−1). ► Analysis completed using the Gora/Watson formalism for an asymmetric top.