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  • 11
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3407-3416 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A theory is presented describing the proposed phonon perturbed photon echo experiment. This experiment is a combination of picosecond time scale stimulated Raman pumping and photon echo experiments. The theory demonstrates that the phonon perturbed photon echo can directly measure electronic excitation–phonon coupling matrix elements by observing the influence of a well defined coherent phonon wave on the photon echo signal. The theory predicts that the echo pulse area (integrated intensity) is reduced. The size of this change is related to the strength of the excitation phonon coupling. In addition, a realistic estimate is made of the size of the effect, and it is shown that the experiment is feasible with available laser equipment.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 30 (1992), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Sinkhole development affects approximately 15 percent of the land area of the world. Development of new sinkholes is extremely site-specific, but general associations between new sinkhole development and hydrogeologic factors can be established for areas with adequate historical records of sinkhole development. In the Orlando area, east-central Florida, at least 140 sinkholes have developed between 1961 and 1986. The Orlando area is situated on a thickly mantled karst area, and sinkholes form by cover collapse or, less commonly, cover subsidence. On the average, 11 new sinkholes collapse each year. The mean diameter is 30.8 feet and the mean depth is 15.5 feet. Eighty-five percent of the new sinkholes occur in high recharge areas (10 to 15 inches/year) on slightly elevated, sandy ridges. Few or no sinkholes occur in discharge areas where net downward erosion of surficial sediment is very unlikely. Forty-two percent of all new sinkholes occur during April and May when ground-water levels are usually at seasonal low stands. When the potentiometric surface declines 5 feet below its mode, then more sinkholes than expected per unit time begin to occur. When the potentiometric surface declines 10 feet below its mode, then more than 10 times as many sinkholes as expected per unit time begin to occur. Management of ground-water withdrawal to avoid drawdowns in excess of 5 feet in sinkhole-prone areas will minimize new sinkhole development induced by man.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 4568-4572 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The ArF laser photodissociation dynamics of dimethylzinc at 193 nm have been studied, and their implications for the growth of ZnSe thin films are discussed. A broadband, vacuum ultraviolet argon plasma emission has been used to acquire time-resolved absorption profiles from ground-state Zn atoms and methyl radicals. Time-resolved fluorescence from excited CH radicals has also been studied. The results indicate that the Zn concentration remains constant from 100 ns to 2 ms after the dissociating ArF pulse, indicating that this system is a good source for free Zn atoms. The CH3 radicals are formed immediately after the dissociation pulse and recombine within several hundred microseconds to form ethane. There was no indication of monomethylzinc (MMZn) formation, and the detected CH radical is likely to combine with H2 to form CH3 within several microseconds. This implies that the major sources for carbon contamination in the growth process (CH3, MMZn, CH) are unlikely to reach the growth surface.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 946-954 
    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
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  • 17
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 62 (1991), S. 2100-2104 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A multichannel single photon counting detection system for steady state, time-resolved luminescence spectra, time-gated imaging, or time-gated Raman is described. This system, which has approximately 80 ps time resolution, is based on a microchannel plate photomultiplier with a position-sensitive anode (Mepsicron). This detector can operate at very low light levels with excitation wavelengths from 200 nm to the near infrared. For time-resolved luminescence applications, the system simultaneously collects 1024 decays of up to 1024 spectral channels. The measured time dispersion for spectral bandwidths greater than 100 nm are shown to be negligible.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4469-4470 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low frequency noise in patterned NiFe/Co/Cu/Co/FeMn (ΔR/R〉9%) spin valves was investigated. The spin valves were sputter deposited and patterned by lift-off to form 75 μm×1000 μm lines. Noise power spectra were measured in the frequency range from 1 Hz to 10 kHz for ac and dc fields applied both parallel and perpendicular to the easy axis. An increase in the low frequency noise power spectrum was observed for an ac field applied along the easy axis. Increasing the ac drive frequency from 500 Hz to 5 kHz reduced the low frequency noise power to near the zero field background level. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 3898-3905 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge buildup in thermally grown SiO2 thin films due to Fowler–Nordheim tunneling has been investigated. Both positive and negative oxide charge can be generated by the tunneling current. The stress fluence, voltage amplitude, and polarity dependence of the positive charge generation points to impact ionization occurring near the oxide substrate interface as the most likely source of this charge. The centroid location and density of the negative oxide charge are used to analyze the negative charge generation process at different stress voltage levels and temperature. A theoretical model is proposed and compared with the experimental data. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 91 (1987), S. 1704-1707 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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