Two-photon spectroscopy of styrene: detection of the 3p Rydberg states

Resonance enhanced multiphoton ionization spectroscopy, (2+1) REMPI, has been employed in jet cooled styrene vapors for the detection of Rydberg states. A resonance appears at 50,484 cm−1 and is interpreted as a 3p←HOMO Rydberg transition (δ=0.52). The 3s state was not detected in the REMPI experiments. The comparison of the experimental spectrum of styrene, in the energy region 5.3-6.6 eV, with two theoretical works from the literature (CASPT2 and SAC-CI) shows that the CASPT2 results are very close to the experiment and more reliable than the SAC-SI.