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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 2158-2166 
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Using a simple isomorphism between the symmetric and antisymmetric Fock space over L2(Rd) and the Wiener isomorphism, a unitary mapping U(s)AB:A(Hs)→L2R(S'R(Rd), dφsR) is constructed, yielding an isomorphism Ws,l(large-closed-square)A(Hsl)⊗A(Hsl)→L2R (SC(Rd)l,dlμsR), where Hs Sobolev space of order s, dφs Gaussian measure on the real Schwartz distributions with covariance operator (−Δ+1)s, dμs=dφs⊗dφs. Using W−1/2,4, the fields are constructed on L2(S'C(R4)4,d4μ−1/2R), yielding a functional integral representation for the two point function of the Euclidean Dirac field with a true Gaussian measure.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 3254-3256 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated a two-dimensional photonic band structure based on macroporous silicon with individual gaps for both polarizations in the infrared region between 250 and 500 cm−1 (20–40 μm). A square lattice of circular air rods with a lattice constant of 8 μm was etched 340 μm deep in an n-type silicon substrate by electrochemical pore formation in hydrofluoric acid. The transmission spectra between 50 and 650 cm−1 were in good agreement with the theoretical calculated structure. The pore formation technique should allow the fabrication of photonic lattices with a complete two-dimensional band gap in the middle and near infrared. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 943-945 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: To improve the stability of porous Si (PS) prepared by electrochemical etching, we make use of rapid-thermal oxidation (RTO). During RTO processing, the hydride coverage of the internal surfaces of the pores is replaced by a high-quality oxide while retaining nm-sized Si grains. With increasing process temperature Tox the luminescence is first quenched. It is recovered with comparable intensity for Tox≥700 °C.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2027-2029 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: High quality aluminum films are deposited using a two-step process. KrF-laser mask patterned palladium catalyst areas are selectively covered with aluminum using triethylamine alane as precursor. The precursor is supplied directly in the liquid phase, so this technique can also work under atmospheric pressure conditions in an inert gas atmosphere. One micrometer thick aluminum metal films can be generated spatially selective with high deposition rate (t(approximately-less-than)10 s).
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 856-858 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Porous silicon layers grown on nondegenerated p-type silicon electrodes in hydrofluoric acid electrolytes are translucent for visible light, which is equivalent to an increased band gap compared to bulk silicon. It will be shown that a two-dimensional quantum confinement (quantum wire) in the very narrow walls between the pores not only explains the change in band-gap energy but may also be the key to better understanding the dissolution mechanism that leads to porous silicon formation.
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  • 6
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate a new route to the synthesis of InAs monolayer structures in GaAs by bridging the fundamental gap between the requirement of the lowest possible substrate temperatures to suppress In segregation and the necessity to maintain sufficiently high temperatures for the growth of low-defect density material. This mediation between opposing aspects of the molecular beam epitaxy of these InAs structures is achieved by a modulation of the substrate temperature and by a minimization of the amount of GaAs cap material grown at low temperature. High-resolution x-ray diffraction and high-resolution electron microscopy combined with photoluminescence (PL) and PL excitation spectroscopies reveal excellent structural properties for our series of (311) and (100) oriented submonolayer and monolayer structures. A comparison of our PL results with already published data proves our In concentration profiles to be very sharp and from a numerical analysis we deduce an upper limit of 0.2 for the In segregation probability in these structures. In addition we obtain as upper limits for the conduction band offsets Q(100)c≤0.4 and Q(311)c≤0.55 for (100) and (311) orientations, respectively.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 2781-2785 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The deep-level transient spectroscopy (DLTS) method is optimized for the observation of radiation damage in semiconductors. A new isothermal variation of the technique is applied to the study of displacement defects in GaAs in order to determine threshold energies and displacement cross sections. A pronounced anisotropy is found for the threshold energy. A linearly increasing displacement probability function is shown to properly model the displacement cross section in 〈100(approximately-greater-than) direction, as compared with the 〈111(approximately-greater-than) direction which requires only a simple step function. Anisotropy leads to a tailing off in the displacement cross section at energies below an "effective'' threshold of about 15.5 eV in the 〈100(approximately-greater-than) direction, indicating that the 〈111(approximately-greater-than) direction is more sensitive to displacement damage than the 〈100(approximately-greater-than) direction. Differences in the damage between these two directions are as large as a factor of 2.
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  • 8
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 10725-10733 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High resolution IR spectra of the linear HCCCN–HCCH and HCN–HCCCCH hydrogen bonded complexes have been obtained using optothermal detection molecular beam techniques. Two vibrational bands have been observed for each complex, which correspond to the terminal "free'' C–H stretch vibrations (ν2) of the cyano units and the hydrogen bonded vibrations (ν3) of the acetylenic CH stretches. For both complexes, accurate molecular constants have been obtained. Furthermore, predissociation lifetimes for the ν3=1 states of the both complexes have been determined. The results are compared with those of the linear HCN–HCCH complex obtained by Block et al. [Chem. Phys. 139, 15 (1989)]. © 1996 American Institute of Physics.
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  • 9
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The high sensitivity of cavity ring-down spectroscopy has allowed us to observe a few perpendicular vibrational overtone transitions of HCN in the visible. These transitions display a sizable Herman–Wallis effect, that is an asymmetry in the relative intensities of the R and P branch lines. We have developed a theory for the first-order Herman–Wallis effect based upon using variational vibrational wave functions but treating the vibration–rotation interaction by first-order perturbation theory. In the specific case of perpendicular transitions, the first-order effect is dominated by Coriolis mixing of Σ and Π overtone states. We used the empirical energy surface by Carter, Mills, and Handy [J. Chem. Phys. 99, 4379 (1993)] restricted to the stretching degrees of freedom. Bending was included by multiplication of these stretching wave functions by harmonic wave functions of the bend. Vibrational transition moments were calculated using a polynomial surface fit to ab initio CCSD(T) dipole moment points by Botschwina et al. [Chem. Phys. 190, 345 (1995) and private communication]. We expected that this treatment would be accurate but the calculated Herman–Wallis effect is about one order of magnitude too large. To gain further insight into the poor agreement between theory and experiment, we have calculated the sensitivity of the Herman–Wallis coefficient and of the transition moment to the dipole and energy surface parameters. From this, it appears that the dipole surface, while producing accurate band intensities, could at the same time be inadequate to account for the Herman–Wallis effect. A similar possibility stands for the energy surface, which however is highly constrained by the requirement to fit the observed band origins. © 1996 American Institute of Physics.
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  • 10
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the high resolution spectrum of the ν1 fundamental of propyne near 3335 cm−1 obtained using a very warm free jet expansion in our optothermal detection spectrometer. By using a high concentration sample expanded at low backing pressures we have been able to observe transitions for K values up to K=6. The additional data available allow us to reinvestigate this vibrational band. We find an unusual perturbation pattern in this band where the individual subbands (rovibrational transitions for a single K value) appear to be completely unperturbed at the level of precision of our data (7.5 MHz), but the subband origin orderings are perturbed through nonresonant interactions. Attempts to account for the subband ordering using a two-state anharmonic interaction are unsuccessful indicating that the perturbations are of multistate origin. This type of nonresonant perturbation to the subband origins of symmetric top molecules should be a common feature of symmetric tops with large A rotational constants. As a result of this investigation we conclude that the previously reported value of αA, determined from a very cold expansion where only K=0 and K=1 were observed, is not a measure of the true (unperturbed) value of this constant. This conclusion is also supported by force field calculations presented here that use an empirical harmonic force field augmented by diagonal anharmonicities for the hydride stretches. These calculations, which reproduce measured values of αA and αB for lower energy bands quite successfully, also show that the previous determination of αA is too large and must be dominated by perturbation contributions. We have also measured the weak Fermi resonant band ν3+2ν09 which acquires its intensity through interaction with ν1. Again we find an anomalous subband ordering like that observed in ν1.
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