title: Femtosecond spectroscopic studies of the one- and two-photon excited-state dynamics of 2,2,17,17-tetramethyloctadeca-5,9,13-trien-3,7,11,15-tetrayne: a trimeric oligodiacetylene.
abstract: The excited-state dynamics of an oligomer of polydiacetylene, 2,2,17,17-tetramethyloctadeca-5,9,13-trien-3,7,11,15-tetrayne, dissolved in n-hexane have been studied by femtosecond fluorescence upconversion and polarized transient absorption experiments under one- and two-photon excitation conditions. Spectroscopically monitoring the population relaxation in the excited states in real time results in a distinct time separation of the dynamics. It has been concluded that the observed dynamics can be fully accounted for on the basis of the two lower excited states of the target molecule. The S1 (2(1)Ag) state, which cannot be excited from the ground state with one-photon absorption, is verified to be populated via internal conversion in 200+/-40 fs from the strong dipole-allowed S2 (1(1)Bu) state. The population in the "hot" S1 state subsequently cools with a time constant of 6+/-1 ps and decays back to the ground state with a lifetime of 790+/-12 ps.
authors.affiliation: Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.
authors.forename: Grzegorz M
authors.initials: GM
authors.lastname: Balkowski
authors.forename: Michiel
authors.initials: M
authors.lastname: Groeneveld
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Cindy C J
authors.initials: CC
authors.lastname: Hendrikx
authors.forename: Michael
authors.initials: M
authors.lastname: Polhuis
authors.forename: Han
authors.initials: H
authors.lastname: Zuilhof
authors.forename: Wybren J
authors.initials: WJ
authors.lastname: Buma