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  • 1
    Electronic Resource
    Electronic Resource
    Investigation of orbital momentum profiles of methylpropane (isobutane) by binary (e,2e) spectroscopy (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 882-888 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Momentum profiles of the valence orbitals of methylpropane, also known as isobutane (CH3CH(CH3)CH3), have been studied by using a high resolution binary (e,2e) electron momentum spectrometer (EMS), at an impact energy of 1200 eV plus the binding energy, and using symmetric noncoplanar kinematics. The coincidence energy resolution of the EMS spectrometer is 0.95 eV full width at half-maximum. The experimental momentum profiles of the valence orbitals are compared with the theoretical momentum distributions calculated using Hartree–Fock (HF) and density functional theory (DFT) methods with the two basis sets of 6-31G and 6-311++G**. The B3LYP functionals are used for the DFT calculations. In general, the experimental momentum distributions are well described by the HF and DFT calculations. The pole strengths of the main ionization peaks from the orbitals in the inner valence are estimated. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1321313
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  • 2
    Electronic Resource
    Electronic Resource
    Overtone spectroscopy of methyl C–H stretch vibration in CH3CF2Cl and CH3CFCl2 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 4111-4117 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Photoacoustic spectra of the second (3νCH), third (4νCH), and fourth (5νCH) overtones of the methyl C–H stretches in CH3CF2Cl and CH3CFCl2 were measured. The spectra are characterized by a multiple peak structure of partially resolved triplets and quartets with an anomalous linewidth decrease in the 4νCH region. The results are interpreted in terms of a simplified local mode model for C–H stretching vibrations, including also the stretch-deformation Fermi resonances. The model accounts for most spectral features and allows determination of the time scale for vibrational redistribution. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480959
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  • 3
    Electronic Resource
    Electronic Resource
    Acetylenic C–H and methyl C–D bond fission in photodissociation of vibrationally excited propyne-d3 (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 5134-5137 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational preexcitation of a state containing three quanta of C–H stretch (3ν1) results in C–H acetylenic and C–D methyl bond rupture in the ∼243.1 nm photolysis of CD3C(Triple Bond)CH, in contrast to previous observations of the almost isoenergetic 193 nm photodissociation of propynes. The C–D bond fission is the dominant pathway with a D/H branching ratio of 2.0±0.5 at a combined energy of ∼50 830 cm−1. The average translational energies of D and H atoms are nearly identical, although the C–H acetylenic and C–D methyl bond energies differ quite extensively, pointing to different dynamics on the involved potential energy surfaces. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1312282
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  • 4
    Electronic Resource
    Electronic Resource
    Single molecule vibrational spectroscopy and microscopy: Cu(II) etioporphyrin-I on Cu(001) (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 4837-4839 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A scanning tunneling microscope was used to perform inelastic electron tunneling spectroscopy on single Cu(II) etioporphyrin-I molecules. The resulting vibrational spectra showed an increase in ac tunneling conductance at 359 mV. This change was attributed to the vibrational excitation of the methene bridge C–H stretch mode. Vibrational microscopy was used to image the spatial distribution of the inelastic tunneling channels involved in this excitation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1311278
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  • 5
    Electronic Resource
    Electronic Resource
    Vibrationally excited states of CH3CFCl2: Intramolecular vibrational redistribution and photodissociation dynamics (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 10787-10795 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Utilizing vibrationally mediated photodissociation of jet-cooled CH3CFCl2 enabled monitoring of the second (3νCH) and third (4νCH) overtones of the methyl in the ground electronic state. The excited molecules are photodissociated by ∼235 or 243.135 nm photons that further tag Cl(2P3/2)[Cl] and Cl(2P1/2)[Cl*] isotopes or H photofragments via mass selective (2+1) resonantly enhanced multiphoton ionization. The vibrational spectra are characterized by a multiple peak structure related to C–H stretches and to Fermi resonating levels involving the CH3 deformation. The cooling in the expansion reduces the rotational and vibrational congestion and affords a determination of the splittings and the upper limits for homogeneous broadening of the transitions. The highest-frequency peak of 4νCH exhibits an additional splitting, related to coupling of the mixed stretch–deformation states with other modes of the molecule. The yield of all three photofragments increases as a result of preexcitation, demonstrating that the energy is not preserved in the excited bond but rather flows to the C–Cl bond. The initial vibrational state preparation not only enhances C–Cl and C–H bond cleavage but also affects the Cl*/Cl branching ratio, as compared to the nearly isoenergetic one-photon 193 nm photolysis of vibrationless ground state CH3CFCl2, implying that it alters the photodissociation dynamics. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.481752
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  • 6
    Electronic Resource
    Electronic Resource
    Laser ablation of solid substrates in water and ambient air (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 2400-2403 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Laser ablation of solid substrates in ambient air and under water is investigated. It is found that the laser ablation rate is highly enhanced by the water film. A wide-band microphone is used to detect the audible acoustic wave generated during laser ablation. Peak-to-peak amplitude of the acoustic wave recorded in water confinement regime (WCR) is greater than that recorded in ambient. It is assumed that the plasma generated in WCR induces a much stronger pressure. This high-pressure, high-temperature plasma results in a much higher ablation rate. Theoretical calculation is also carried out to verify this assumption. By proper calibration, acoustic wave detection can be used as a real-time monitoring of the laser ablation. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1342200
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  • 7
    Electronic Resource
    Electronic Resource
    Some features of chaos and oscillations in plasma-filled diodes (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 7 (2000), S. 3976-3982 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The physical background concerning the existence of four dynamical states (stable, oscillatory, chaotic and unstable) in a plasma-filled diode has been investigated in some detail, the results being presented with the help of charge density and other three-dimensional graphs. It has been established that the determining factor is a dynamic ions/electrons charge-balance in the interelectrode space. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1289028
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  • 8
    Electronic Resource
    Electronic Resource
    Characterization of CaTiO3-modified Pb(Mg1/3Nb2/3)O3 dielectrics (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 2516-2519 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pb(Mg1/3Nb2/3)O3 dielectrics modified by CaTiO3 were prepared by a solid-state reaction method, and microstructure analyses were performed together with the dielectric characterization. Solid solutions with cubic perovskite structures were obtained for compositions of 0–60 mol %CaTiO3, and the orthorhombic perovskite structures were observed for compositions near to the end member of CaTiO3 in the present system. The dielectric loss and temperature coefficient could be pronouncedly reduced by incorporating CaTiO3 into Pb(Mg1/3Nb2/3)O3. Low-loss dielectrics (tan δ∼10−4 at 1 MHz) with dielectric constants of 120–262 and small temperature coefficient (τε∼−960 to −1100 ppm/ °C) were obtained, and further improvement of dielectric properties could be expected through structural modifications. Good microwave dielectric properties, ε=172.6 and Qf=1930 GHz, were achieved in a composition of 0.4Pb(Mg1/3Nb2/3)O3/0.6CaTiO3, where the temperature coefficient of resonant frequency τf was estimated as 470 ppm/ °C. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372212
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  • 9
    Electronic Resource
    Electronic Resource
    A deep level transient spectroscopy study of beryllium implanted n-type 6H-SiC (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 4558-4562 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Beryllium implantation induced defects in 6H-SiC pn junctions have been investigated by deep level transient spectroscopy. Five defect centers labeled BE1, BE2, BE3, BE4, and BE5 have been detected in the temperature range 100–450 K. A comparative study has also been performed in low beryllium doped n-type 6H-SiC, which proved that the BE1, BE2, and BE3 centers are electron traps located at 0.34, 0.44, and 0.53 eV, respectively, below the conduction band edge. On the other hand, the BE4 and BE5 centers have been found to be hole traps which are situated at 0.64 and 0.73 eV, respectively, above the valence band edge. Possible defect configurations associated with these deep levels are discussed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287232
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  • 10
    Electronic Resource
    Electronic Resource
    Direct interband transitions in tris-(8-hydroxyquinoline) aluminum thin films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 1082-1086 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electroluminescent properties of three different device structures (A:ITO/SiO2/Alq3/SiO2/Al, B:ITO/Alq3/SiO2/Al, and C:ITO/SiO2/Alq3/Al) based on the tris-(8-hydroxyquinoline) aluminum (Alq3) were investigated. A blue electroluminescence at 457 nm was obtained from device (A) and (B), and the green emission at 518 nm was obtained from device (C). It is generally agreed that the green emission originates from the recombination of the singlet excitons. The blue emission, here, is attributed to the direct transitions between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital of Alq3. This is due to the electric field-induced excitons dissociation and the space charge accumulation at the interface. The high internal electric field enhances the dissociation of neutral singlet excitations into LUMO states and inhibits the formation of the singlet excitons, therefore enhances the probability for direct interband transitions of the relaxed carriers. The intensity of the blue emission is dependent on the operating frequency. This indicates that space charge accumulation time and effective internal electric field are responsible for the blue emission intensity. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1334635
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