biostudies-literatureZhang JEuropean Research Council1613-1620https://www.ebi.ac.uk/biostudies/studies/S-EPMC12908150biostudies-literatureUnknown17(6)The prototypical polyene-like β-carotene molecule displays a substantial electric polarizability but a negligible electric dipole moment in the electronic ground state. Changes of such quantities in excited states of β-carotene have remained unknown in liquid and/or protein environments fluctuating at ambient temperature. Here, we study the polarizability and dipole changes of β-carotene in apolar <i>n</i>-hexane by ultrafast terahertz (THz) Stark spectroscopy. An external picosecond THz electric field induces a pronounced red-shift of electronic absorption on the optically allowed transition from the 1¹A_g ground state to the 1¹B_u excited state. We derive an increase in polarizability of Δα = 450 ± 80 ų in the 1¹B<sub>u</suThe journal of physical chemistry lettersTransient Electronic Polarizability of β-Carotene from Ultrafast Terahertz Stark Spectroscopy.PMC12908150101125590Fingerhut BPZhang JElsaesser TJaschke CfalseTransient Electronic Polarizability of β-Carotene from Ultrafast Terahertz Stark Spectroscopy.The prototypical polyene-like β-carotene molecule displays a substantial electric polarizability but a negligible electric dipole moment in the electronic ground state. Changes of such quantities in excited states of β-carotene have remained unknown in liquid and/or protein environments fluctuating at ambient temperature. Here, we study the polarizability and dipole changes of β-carotene in apolar <i>n</i>-hexane by ultrafast terahertz (THz) Stark spectroscopy. An external picosecond THz electric field induces a pronounced red-shift of electronic absorption on the optically allowed transition from the 1¹A_g ground state to the 1¹B_u excited state. We derive an increase in polarizability of Δα = 450 ± 80 ų in the 1¹B<sub>u</su2026-01-01T00:00:00Z2026 Feb2026-07-15T22:12:24.399Z2026-07-09T10:20:59.245ZS-EPMC129081504160549610.1021/acs.jpclett.5c03702