Polarization-Resolved Pump-Probe Method To Determine The Excited-States Of Polymethine Molecules

A pump-probe method based on excited-state transition dipole moment orientations is used to determine the energies of the excited-states of polymethine molecules. The results are compared to the steady-state fluorescence anisotropy technique with good agreement. ©2002 Optical Society of America

Orientation Of Transition Moments In Excited-State Absorption Of Polymethine And Squarylium Dyes

Orientation of transition moments, in excited-state absorption of polymethine and squarylium dyes, was studied. A pump-probe geometry, in which the probe polarization was fixed and pump polarization could be rotated using a half-wave plate method, was used. The laser system used consisted of a Ti:sapphire amplified erbium-doped fiber ring oscillator system followed by two optical parametric generator/amplifiers. Results indicated that excited state transition dipole moments were near parallel to the ground state to excited state transitions

Transient Excited-State Absorption and Gain Spectroscopy of a Two-Photon Absorbing Probe with Efficient Superfluorescent Properties

The synthesis, linear photophysical properties, two-photon absorption (2PA), excited-state transient absorption, and gain spectroscopy of a new fluorene derivative tert-butyl 4,4′-(4,4′ (1E,1′E)-2,2′-(9,9-bis(2- (2-ethoxyethoxy)ethyl)-9H-fluorene-2,7-diyl)bis(ethene-2,1-diyl)bis(4,1 phenylene)]dipiperazine-1-carboxylate (1) are reported. The steady-state linear absorption and fluorescence spectra, along with excitation anisotropy, fluorescence lifetimes, and photochemical stability of 1 were investigated in a number of organic solvents at room temperature. The 2PA spectra of 1 with a maximum cross-section of ~ 300 GM were obtained with a 1 kHz femtosecond laser system using open-aperture Z-scan and two-photon-induced fluorescence methods. The transient excited-state absorption (ESA) and gain kinetics of 1 were investigated by a femtosecond pump-probe methodology. Fast relaxation processes (~1–2 ps) in the gain and ESA spectra of 1 were revealed in ACN solution, attributable to symmetry-breaking effects in the first excited state. Efficient superfluorescence properties of 1 were observed in a nonpolar solvent under femtosecond excitation. One- and two-photon fluorescence microscopy imaging of HCT 116 cells incubated with probe 1 was accomplished, suggesting the potential of this new probe in two-photon fluorescence microscopy bioimaging