Fluorescence excitation spectra, Raman spectra and structure of isochroman in its S1 (π, π∗) state

► First attempt to find the structure of isochroman in S0 and S1 states. ► Fluorescence excitation spectrum and Raman spectrum of isochroman in jet. ► The “twisted” structure is found to be the optimized structure in both S0 and S1. ► The spectra are explained. ► A few vibrational modes are observed in S1 and assigned.