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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 104 (1996), S. 805-811 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a comparative study on the ultrafast nonlinear optical response of a novel conjugated zinc porphyrin system. The linear optical absorption spectra of these molecules all show the Q-band and B-band transitions of the basic porphyrin unit. We have taken spectrally resolved ultrafast pump–probe measurements on monomer, dimer, and polymer solutions, which allows us to compare their excited state dynamics and relate these to their linear optical absorption. The spectra show several common features, but these features have markedly different decay dynamics. The bleaching is preferential in the Q band for the polymer and the B band for the monomer. The polymer Q-band bleaching shows a two-component decay, of approximately 700 fs and 170±50 ps time constants in a biexponential fit, which we attribute to both exciton–exciton annihilation and exciton diffusion to recombination centers on the polymer chain. The Q band of the dimer also has a two-component decay with 13±5 and 1250±70 ps time constants which we attribute to rotational diffusion of the excited molecule in solution, and decay to the ground state, respectively. The B-band bleaching in the monomer is long lived and has a decay constant of approximately 3.5±0.5 ns; from the absorption recovery of the B band we estimate a triplet yield of 0.8. All molecules exhibit broad π*−π* absorptions in the visible spectral region (between the Q band and the B band). In particular, we show that the monomer has potential as a broadband optical limiter in the visible region from 455 (2.72 eV) to 620 nm (2.00 eV); we estimate that its excited state absorption cross section is 8.5 times that of its ground state cross section at 532 nm (2.33 eV). There is also clear evidence of triplet transitions in the dimer and monomer; the triplet absorption feature ranging from 940 (1.32 eV) to 1000 nm (1.24 eV) rises 10 ps after excitation in the dimer which suggests a short intersystem-crossing time. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 238-240 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report measurements of the polarization and time-averaged intensity of four-wave mixing signals from GaAs quantum wells as functions of the pump beam polarizations, laser photon energy, and optical injection density, the latter covering a range of higher levels than has previously been reported. Excitation of heavy-hole excitons produced a sin2 variation of the signal intensity as the pump beam polarizations changed from parallel to perpendicular, while injection of light-hole excitons led to an approximately cos2 dependence. The tuning dependence of the heavy-hole-exciton signal revealed a low-energy signal which is attributed to biexcitons. The dominance of this signal for perpendicular polarization causes the observed sin2 variation of the heavy-hole-exciton signal. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 3214-3218 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structure of the optical phase change memory alloy, silver–vanadium–indium–antimony–tellurium (AVIST), has been investigated by the methods of optical reflectivity change, Raman spectroscopy, and electron diffraction. In order to identify each phase, Sb, AgSb, AgSbTe, and AgInTe films were also studied. The Raman spectrum of an AVIST thin film annealed at 523 K for 1 h in Ar gas, shows two main broad peaks around 116 and 150 cm−1. These peaks appear to be related to Sb vibration modes in the AVIST alloy, but their relative intensities are reversed for the AVIST films in comparison with those for a Sb film. Furthermore, in AVIST, the peak at 116 cm−1 shifts to lower wave number when the vanadium content is increased from 0.4 to 4.7 at %. The electron diffraction pattern of AVIST alloy indicates that the AgSbTe2 crystalline phase dominates rather than Sb. A model of the structure of AVIST consistent with these observations is proposed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 889-891 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron-LO phonon scattering time in GaAs-Al0.33Ga0.67As quantum wells is determined to be 200±50 fs using transient absorption with low excitation density, a more direct method than previous measurement techniques.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    Modern Asian studies 11 (1977), S. 152-154 
    ISSN: 0026-749X
    Source: Cambridge Journals Digital Archives
    Topics: Ethnic Sciences , History , Political Science , Economics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    Modern Asian studies 14 (1980), S. 93-109 
    ISSN: 0026-749X
    Source: Cambridge Journals Digital Archives
    Topics: Ethnic Sciences , History , Political Science , Economics
    Notes: Japanese interest in Hainan stemmed from the desire to emulate the success which they had achieved in Taiwan in an area further south which could offer a full range of tropical products for theuse of the Japanese economy. The naval importance of Hainan was also recognized, because it could dominate the South China Sea from the excellent harbour of San-ya ([...] Samah) Bay, and there were indications that the island was rich in minerals. The development of official Japanese interest in the island was largely the work of the governor-general's office in Taiwan. Thus in 1918 and 1919 an official from Taiwan called Kaku ([...]) was sent to Hainan to observe conditions under the title of special sales office head. In the 1920's the Taiwan government sponsored conferences o the South China Japanese consuls to discuss plans for the area, and in 1935 a conference was held production in the tropics, to coordinate research on the economy, production possibilities and culture of the tropical part of China.Meanwhile Chinese government interest in Hainan began to be aroused in the 1930's, culminating in the visit of T.V. Soong, one of the highest ministers of e Kuintang government, in 1936. Thereafter a rail route a west of the island was surveyed but no furthe progress was made. Private businessmen in the 1930's began to develop rubber plantations to join those set up with overseas Chinese capital in the 1910's,and there was a sharp rise in the area planted to sugar in 1936 as the price of sugar rose. Hence when war broke out between China and Japa,the possibilities for the development were just beginning to be explored.1
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of a theoretical and experimental investigation of resonant Mandelstam-Brillouin light scattering by thermal acoustic phonons with k=0 near the direct absorption edge (in the case of ZnSe crystals) are analyzed. The appearance of a new type of resonant increase in the intensity of Raman scattering by optical phonons with k≠0, which corresponds to resonance with the scattered light in the output channel, near the indirect absorption edge (in the case of semi-insulating GaP:N crystals) is also reported. The resonant gain reaches ∼4×103 at frequencies corresponding to overtone scattering assisted by LO(X) and LO(L) phonons. Exciton states belonging to both discrete exciton bands and to the continuous spectrum are considered as the intermediate states involved in the scattering processes in calculations of the resonant scattering tensors. In addition, all the intraband transitions, as well as the interband transitions between the conduction band, the valence bands, and the spin-orbit split-off band are taken into account, and good agreement with the experimental results is obtained.
    Type of Medium: Electronic Resource
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