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  • 1
    Electronic Resource
    Electronic Resource
    Wave-packet dynamics in a cyanine dye molecule excited with femtosecond chirped pulses (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 7546-7553 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Femtosecond vibrational wave-packet dynamics in a cyanine molecule is observed to be strongly dependent on the chirp direction of the excitation pulse. The slow-decay component associated with an oscillatory structure, which corresponds to the excited-state lifetime and a vibrational mode of 160±10 cm−1, respectively, is measured by the femtosecond time-resolved transmission spectroscopy. The excited-state population is substantially decreased and enhanced in the cases of negatively chirped (NC) and positively chirped (PC) excitations, respectively. A quantum mechanical calculation by means of the split operator scheme is performed to reproduce the wave-packet propagation after the chirped pulse excitation. The calculation shows that the spatial distribution of the wave packet for the NC case is narrower than that for the PC case during the excitation, and that the overlap integral between the excited- and ground-state wave packets determines the efficiency of the population dumping. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1313542
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  • 2
    Electronic Resource
    Electronic Resource
    Complex electro-optic constants of dye-doped polymer films determined with a Mach–Zehnder interferometer (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 4935-4940 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The real and imaginary parts of the linear electro-optic (EO) constants of four dyes, i.e., N,N-dimethylaminonitrostilbene (DANS), 4-[N-(2-hydroxyethyl)-N-ethyl]amino-4'-nitroazo- benzene [disperse red 1 (DR1)], N,N-dimentylindoaniline [phenol blue (PB)], and 1,1',3,3,3',3'-hexamethylindotricarbocyanine iodide (HITCI) in polymethylmethacrylate (PMMA) films were determined using a Mach–Zehnder interferometer. The electronic transitions of DANS, DR1, PB, and HITCI are off-resonant, near-resonant, and resonant on the higher and lower energy sides with a He-Ne laser wavelength (632.8 nm), respectively. The different ratios of the real and imaginary parts of the EO constants of four dyes including their signs are successfully explained in terms of detuning energy. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359299
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  • 3
    Electronic Resource
    Electronic Resource
    Ultrafast exciton and excited-exciton dynamics in J-aggregates of three-level porphyrin molecules (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 5844-5850 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We observed the ultrafast response of exciton (S1-exciton) and excited-exciton (S2-exciton) in one-dimensional J-aggregates of three-level porphyrin molecules by femtosecond pump–probe spectroscopy. The decay profiles of the nonlinear response can be fitted to a sum of instantaneous response and two exponential decay components with time constants of 1.3±0.1 and 40±1 ps. The former and latter were found to correspond to the lifetimes of S2- and S1-excitons, respectively. The origins of the nonlinearity were attributed to the following three contributions: (1) coherent effects between the pump and probe via one-photon virtual S1-exciton, (2) induced absorption of real S2-excitons generated by two photons, and (3) induced absorption of real S1-exciton. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478483
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  • 4
    Electronic Resource
    Electronic Resource
    Superradiance quenching by confined acoustic phonons in chemically prepared CdS microcrystallites (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 4131-4140 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the luminescence spectrum and picosecond dynamics of excitons in CdS microcrystallites embedded in an acrylonitrile–styrene copolymer film by a new method. The intensity ratio of band-edge emission due to the direct recombination of excitons to red-shifted emission from the trapped states was much larger than any other samples previously reported. This indicates much higher quality of our microcrystallites. From the comparison of luminescence spectrum of samples prepared by different cadmium salts as raw materials, we propose a "site–substitution'' model for the origin of the trapped states. According to the model, the trapped states yielding the red-shifted emission are impurities substituting the sulfur sites. The band-edge emission was found to be emitted mainly from the larger microcrystallites among the size distribution. The luminescence lifetime of the band-edge emission was almost constant at 60 ps below a threshold temperature (45±5 K) and increases nearly proportionally with temperature above this temperature. This temperature dependence of the lifetime suggests the quenching of superradiance of excitons by acoustic phonons confined in the microcrystallites. The threshold temperature corresponds to the frequency of radial compression mode (30.0 cm−1=43.2 K) of the spherical microcrystallites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460646
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  • 5
    Electronic Resource
    Electronic Resource
    New fabrication method for highly oriented J aggregates dispersed in polymer films (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 577-579 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present a new fabrication method, called "vertical spin coating,'' to prepare highly oriented J aggregates dispersed in polymer films. Linear dichroic spectra of the oriented J aggregate of 1,1'-diethyl-2,2'-quinocyanine bromide PIC-Br were measured at 5 K. The dichroic ratio at the peak of J band was 5 to 10, dependent on the preparation conditions. Precise measurement of the dichroism at the J band revealed that the J band is composed of two bands with transition dipole moments perpendicular to each other. The films are stable even at room temperature, and have applications as nonlinear optical devices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109954
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of complex tensor components of electro-optic constants of dye-doped polymer films with a Mach–Zehnder interferometer (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 1605-1607 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The complex electro-optic constants of disperse red 1 (DR1) dye molecules doped in polymethylmethacrylate film were measured by a scanning Mach–Zehnder interferometric technique. Despite a very small absorbance at 632.8 nm, DR1 molecules still have a measurable imaginary part of the EO constants. Two independent complex components, r˜13 and r˜33 were determined by incident angle dependence. The ratios Re[r˜33]/Re[r˜13] and Im[r˜33]/Im[r˜13] are 3.5±0.5 and 3.2±0.9, respectively. These results show that EO response is dominated by the electronic mechanism. The influence of multiple reflection in polymer film on the experimental results are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112925
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  • 7
    Electronic Resource
    Electronic Resource
    Femtosecond inverse Raman spectrum of molecular J-aggregates (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 26 (1995), S. 553-559 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The femtosecond inverse Raman spectrum of J-aggregates of a cyanine dye was studied theoretically and experimentally by the pump - probe experiment. The time dependence of the Raman signal intensity of the aggregates was fitted with an instantaneously responding component due to the Stark effect together with 200 fs and 1 ps lifetime components due to the excitons. The instantaneous response in the time-resolved difference transmission spectrum including the inverse Raman, induced and saturated absorption was successfully reproduced by the calculation under sub-resonant excitation based on the density matrix formalism.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250260710
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