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  • Electronic Resource  (35)
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  • Electronic Resource  (35)
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  • 1
    Electronic Resource
    Electronic Resource
    Lattice theories of polymeric fluids (1989)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 93 (1989), S. 2194-2203 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100343a006
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  • 2
    Electronic Resource
    Electronic Resource
    Luminescence properties of CdSe quantum crystallites: Resonance between interior and surface localized states (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 946-954 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We use time-, wavelength-, temperature-, polarization-resolved luminescence to elucidate the nature of the absorbing and "band edge'' luminescing states in 32 A(ring) diameter wurtzite CdSe quantum crystallites. Time-resolved emission following picosecond size-selective resonant excitation of the lowest excited state shows two components—a temperature insensitive 100 ps component and a microsecond, temperature sensitive component. The emission spectrum, showing optic phonon vibrational structure, develops a ∼70 wave number red shift as the fast component decays. Photoselection shows the slow component to be reverse polarized at 10 K, indicating this component to be the result of a hole radiationless transition. The 100 ps emitting state is repopulated thermally as temperature increases from 10 to 50 K. All available data are interpreted by postulating strong resonant mixing between a standing wave molecular orbital delocalized inside the crystallite and intrinsic surface Se lone pair states. The apparent exciton transition is assigned to a ∼130 wave number wide band of eigenstates with the hole localized principally on the surface. The band contains strongly emitting "doorway'' states and weakly emitting "background'' states. The hole becomes mobile among these states as T increases to 50 K. It is suggested that such resonant mixing may be general in II–VI and III–V crystallites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462114
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  • 3
    Electronic Resource
    Electronic Resource
    X-ray structural characterization of larger CdSe semiconductor clusters (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 7282-7290 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: X-ray powder patterns obtained from three different types of 35–40 A(ring) CdSe nanoclusters are analyzed. We simulate the effects of thermal fluctuations, stacking faults, surface reconstructions, and bond compressions on powder patterns of CdSe clusters using the Debye formula. We find that the spectra of capped and annealed CdSe particles grown in inverse micelles are best fit by a mixture of crystalline structures intermediate between zinc-blende and wurtzite. We describe a new preparation for CdSe clusters, the structure of which appears to be well-defined wurtzite with, on average, less than one stacking fault per cluster. Thermal effects are found to be important and to mask the subtle effects of likely surface and core reconstructions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.457295
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  • 4
    Electronic Resource
    Electronic Resource
    Observation and analysis of the ν3 band of NH+3 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5910-5917 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ν3 degenerate vibration–rotation band of the ammonia cation NH+3 was observed and analyzed. The spectrum was detected in direct absorption using a tunable difference frequency spectrometer combined with velocity modulation. The ion was produced in a 6 kHz ac discharge with a gas mixture of He:H2:NH3 (∼250:8:1) and with a total pressure of ∼6 Torr. Spin–rotation splittings for most Q-branch transitions were well resolved and spin–rotation interaction constants were determined. A symmetric rotor Hamiltonian with A1–A2 splittings and l resonance was used to analyze the spectrum. The spectral pattern indicates that NH+3 is a planar molecular with D3h symmetry, consistent with a 2A‘2 ground electronic state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456356
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  • 5
    Electronic Resource
    Electronic Resource
    Laboratory observation of hot bands of H+3 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6200-6209 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The (2ν2,l=2←ν2), (2ν2,l=0←ν2), and (ν1+ν2←ν1) hot bands of H+3 were observed. The vibrationally hot ions were produced in a liquid nitrogen cooled 6 kHz ac discharge using gas mixtures of H2 and He. The spectra were detected in direct absorption using a newly extended tunable difference frequency spectrometer using both LiNbO3 and LiIO3 crystals as nonlinear optical elements. The range of this spectrometer is now ∼5300–∼1900 cm−1. The positions of the rovibrational transitions compare extremely well with the theoretical predictions of Miller and Tennyson. A vibrational temperature study of the discharge indicates a significant population inversion between the ν1 and ν2 levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458989
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  • 6
    Electronic Resource
    Electronic Resource
    Difference frequency laser spectroscopy of the ν3 fundamental band of NH+2 (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5918-5923 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The ν3 band of NH+2 in the X˜ 3B1 ground electronic state was observed in direct absorption with a tunable difference frequency laser spectrometer in the 3 μ region, using velocity modulation detection. NH+2 and NH+3 ions were generated in an ac discharge of He and NH3, or of He, N2, and H2. Fifty-three rovibrational transitions were measured and fit to a triplet A-reduced Hamiltonian to determine rotational, centrifugal distortion, and spin–rotation constants. The band origin was found to be ν0=3359.932 cm−1, in excellent agreement with a recent calculation of Jensen, Bunker, and McLean. Indirect evidence from the spectrum suggested that NH+2 is quasilinear, but selection rules prevented a determination of the A rotational constant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456357
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  • 7
    Electronic Resource
    Electronic Resource
    Electroluminescence from CdSe quantum-dot/polymer composites (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 1316-1318 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electroluminescence is obtained from nearly monodisperse CdSe nanocrystallites (quantum dots) incorporated into thin films (1000 A(ring)) of polyvinylcarbazole (PVK) and an oxadiazole derivative (t-Bu-PBD) and sandwiched between ITO and Al electrodes. The electroluminescence and photoluminescence spectra (bandwidths ≤40 nm) are nearly identical at room temperature and are tunable from ∼530 to ∼650 nm by varying the size of the dots. Voltage studies at 77 K indicate that while only the dots electroluminesce at the lower voltages, both the dots and the PVK matrix electroluminesce at higher applied voltages. Variable temperature studies indicate that the electroluminescence efficiency increases substantially as the films are cooled down to cryogenic temperatures. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113227
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  • 8
    Electronic Resource
    Electronic Resource
    Electrospray organometallic chemical vapor deposition—A novel technique for preparation of II–VI quantum dot composites (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 2795-2797 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A novel technique combining electrospray and organometallic chemical vapor deposition (OMCVD) has been developed for the synthesis of new II–VI quantum dot composites. CdSe nanocrystals (quantum dots) of selected size are dispersed in a pyridine/acetonitrile mixture. The nanocrystals are transferred by electrospray into the growth zone of an OMCVD reactor and codeposited on a ZnSe matrix grown from hydrogen selenide and diethyl zinc. Composites consisting of CdSe nanocrystals and an amorphous or polycrystalline ZnSe matrix have been deposited on glass substrates at temperatures of 150–250 °C. Room-temperature absorption and photoluminescence spectra show optical transitions characteristic of the initial nanocrystal dispersions. The emission wavelength may be tuned in a broad spectral region by incorporating nanocrystals of varying sizes. The composites have been characterized by Auger electron spectroscopy, high resolution transmission electron microscopy, and scanning transmission electron microscopy. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112568
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  • 9
    Electronic Resource
    Electronic Resource
    Nucleation and growth of cadmium selendie on zinc sulfide quantum crystallite seeds, and vice versa, in inverse micelle media (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 1327-1332 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00160a005
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  • 10
    Electronic Resource
    Electronic Resource
    From amplified spontaneous emission to microring lasing using nanocrystal quantum dot solids (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 1303-1305 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study different emission regimes in close-packed films of chemically synthesized CdSe nanoparticles [nanocrystal quantum dots (NQDs)]. We observe that the NQD photoluminescence is dominated by excitons and biexcitons, respectively, before and after the threshold for stimulated emission. Furthermore, we demonstrate the regime of microring lasing into sharp, whispering-gallery modes using NQD solids incorporated into microcapillary tubes. This result indicates a feasibility of miniature, solid-state laser devices based on chemically synthesized NQDs. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1497708
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