Ultrafast optical dynamics of spiro-compounds

We report on time-resolved measurements of spiro-type molecules in the ps- and fs-timescale. Due to the orthogonality of the transition dipoles of two identical moieties connected through a spiro-atom, one expects these compo unds to show two perpendicular, degenerate states that may enter into a com plex free evolution upon fs excitation. On ps scales the bichromophoric uni ts behave as isolated absorbers, thus their fluorescence stems from localiz ed site populations. Level relaxation gives rise to slightly non-exponentia l relaxation that can be quantified in terms of underlying life-time distri butions by employing numerical Laplace inversion. Fs fluorescence upconvers ion experiments have been employed to elucidate, for the first time, nuclea r and electronic dynamics subsequent to broad-band fs-preparation.