title: Femtosecond Time-Resolved Stimulated Raman Spectroscopy of the S(2) (1B(u)) Excited State of beta-Carotene.
abstract: The electronic and vibrational structure of beta-carotene's early excited states are examined using femtosecond time-resolved stimulated Raman spectroscopy. The vibrational spectrum of the short-lived ( approximately 160 fs) second excited singlet state (S(2),1B(u) (+))of beta-carotene is obtained. Broad, resonantly enhanced vibrational features are observed at approximately 1100, 1300, and 1650 cm(-1) that decay with a time constant corresponding to the electronic lifetime of S(2). The temporal evolution of the vibrational spectra are consistent with significant population of only two low-lying excited electronic states (1B(u) (+) and 2A(g) (-)) in the ultrafast relaxation pathway of beta-carotene.
authors.affiliation: Department of Chemistry University of California, Berkeley, California 94720.
authors.forename: Philipp
authors.initials: P
authors.lastname: Kukura
authors.forename: David W
authors.initials: DW
authors.lastname: McCamant
authors.forename: Richard A
authors.initials: RA
authors.lastname: Mathies