High resolution electronic spectroscopy of p-vinylphenol in the gas phase

A recent controversy regarding the proper assignment of two closely spaced bands in the S1 ← S0 electronic transition of trans-p-coumaric acid (pCA) has been addressed by recording their spectra at full rotational resolution. The results show unambiguously that the carrier of these two bands is p-vinylphenol (pVP), a thermal decomposition product of pCA. The two bands belong to two conformers of pVP; trans-pVP at 33,207.3 cm−1 and cis-pVP at 33,211.8 cm−1.