Electronic ground state conformers of β-carotene and their role in ultrafast spectroscopy

► Calculation of potential energy curve for the rotation of one terminal group of β-carotene. ► The curve exhibits two closely spaced energetic minima. ► Upon excitation of the global minimum, the well know S1 state is formed. ► Excitation of the higher lying local minimum leads to population of the intensely debated S∗ state