Vibrational\nMode-Dependent Circular Dichroism of Jet-Cooled\nStyrene Oxide

Vibrational mode-dependent circular dichroism (CD) effects\nin vibrational\nCD spectra are often used to determine the handedness of molecules\nwith multiple chiral centers. Here, we investigate vibrational mode-dependent\nCD effects in the electronic CD spectra of jet-cooled (<i>R</i>)–(+)– and (<i>S</i>)–(−)–styrene\noxide obtained by using resonant two-photon ionization CD (R2PICD)\nspectroscopy. Although most fundamental vibronic bands demonstrated\nCD signatures consistent with that of the origin band, the overtone\nand combination bands exhibited opposite CD signatures. Theoretical\ncalculations suggest that CD in fundamental bands are primarily governed\nby Franck–Condon contributions, whereas Herzberg–Teller\ncontributions, which reflect the influences of vibrational modes on\nCD values, become more significant in overtone and combination bands.\nThese results underscore the potential of mode-dependent vibronic\nCD signals in R2PICD spectra for determining the absolute configurations\nof molecules with multiple chiral centers.