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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 4819-4825 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We analyzed the optical emissions in the wavelength region 2000–8000 A(ring) produced by dissociative electron impact on CCl2F2. Absolute photoemission cross sections have been determined for a variety of neutral and ionic fluorine and chlorine lines as well as for the strong diatomic CCl and CCl+ bands at 2778 and 2368 A(ring), respectively. In many cases comparisons between experimentally determined appearance potentials and spectroscopic and thermochemical data enabled a unique identification of the underlying break-up mechanism of the parent molecule upon electron impact. Atomic fluorine emissions which are the result of the total fragmentation of the parent molecule dominate the spectrum from 6000 to 8000 A(ring) with absolute emission cross sections in the range of 0.1 to 3.5×10−19 cm2 at 100 eV for individual 3p→3s fine structure lines. The prominent continuous emission between 2200 and 4000 A(ring) was found to consist of two contributions, the D 2B2→X 2B2 emission of the CCl2F+2 parent ion with an appearance potential of 14.2±1.0 eV and a second emission feature with an appearance potential around 42 eV which has not been uniquely identified.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4252-4256 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We studied the continuous emissions in the wavelength range 2000 to 3400 A(ring) produced by low energy electron impact on SF6 and NF3. In both cases two different features contribute to the emission spectrum. In NF3, we found a structured emission with maxima at 2880, 3005, and 3130 A(ring) and an onset energy of 8.5±2 eV superimposed on a continuous feature from 2500 to 3500 A(ring) with an onset at about 30 eV. We attribute the structured emission, which has an emission cross section of 2.2×10−19 cm2 at 25 eV, to the NF2 fragment. In SF6, we observed a broad emission feature from 2000 to 3300 A(ring) with maximum intensity at 3010 and 3145 A(ring) with a comparatively weak shoulder at 3160 A(ring). The 3160 A(ring) feature, which has an emission cross section of about 2×10−20 cm2 at 25 eV, has a single onset at 13.5±1.5 eV, whereas at least two different processes with onsets at 28±2 eV and 42±3 eV, respectively, contribute to the main SF6 emission. The potential relevance of these continuous emissions for diagnostic purposes of NF3 and SF6 processing plasmas utilizing plasma-induced emission spectroscopy and laser-induced fluorescence techniques is discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 1094-1105 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Predissociation of a high-lying 1Σ+ state of NaK is studied using the optical–optical double resonance technique. A single-mode ring dye laser is set to a particular 2(A)1Σ+(v,J)←1(X)1Σ+(v′′,J′′) transition. Another single-mode laser (Ti–sapphire) is then used to excite the molecule from the 2(A)1Σ+(v,J) level, to rovibrational levels of a higher predissociating electronic state, which we identify as 6 1Σ+. The predissociation is monitored by the atomic potassium emission on the 3 2D3/2→4 2P1/2 transition at 1.17 μm, while bound state radiative processes are monitored by total violet fluorescence from the upper state to the various rovibrational levels of the ground 1(X)1Σ+ state. By scanning the Ti–sapphire laser, different rovibrational levels of the 6 1Σ+ state can be excited. The vibrational levels probed range from v=13 to 20 with rotational states ranging from 9 to 99. The bound state energy level positions are measured from the center frequencies of lines recorded with the Ti–sapphire laser excitation scans. The 6 1Σ+ state is then described by the following molecular constants which are calculated from the experimental values of the level energies: Te=25 560.373 cm−1, ωe=89.179 26 cm−1, ωexe=0.730 691 cm−1, Be=0.067 327 0 cm−1, αe=0.000 675 35 cm−1, De=−3.298 31×10−8 cm−1, βel=1.518 17×10−8 cm−1. The potential well depth is De=4416.0 cm−1, if we assume the most likely asymptotic limit of Na(3 2S1/2)+K(5 2P1/2). The equilibrium separation is Re=4.158 Å. We also report measured and calculated intensities (Franck–Condon factors) for the 6 1Σ+→1(X)1Σ+ violet band. The absolute predissociation rates of 6 1Σ+ levels are directly measured from the linewidths recorded on the Ti–sapphire laser excitation scans. We measure predissociation rates ranging up to 9.4×109 s−1. The dependence of the absolute predissociation rates on rovibrational quantum numbers is studied with an attempt to predict the shape of the repulsive potential curve causing the predissociation, its crossing point with the bound state, and the type of perturbative interaction leading to the predissociation. The state causing the predissociation is determined from correlation diagrams to be the continuum of either the 3 3Π, the 3 1Π, or the 5 3Σ+ state with Na(3S)+K(3D) dissociation limit. We measure the collisional broadening rate coefficients of some 6 1Σ+←2(A)1Σ+ lines due to both argon and potassium perturbers, and obtain the average values, kbrAr=(1.1±0.2)×10−8 cm3 s−1 and kbrK=(1.1±0.6)×10−8 cm3 s −1. Velocity-changing collisions and collisional excitation transfer between individual rotational levels of the 2(A)1Σ+ state are also investigated. © 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 67 (1995), S. 1378-1380 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Fabrication of a two-dimensional array of nanometer-scale chromium features on a silicon substrate by laser-focused atomic deposition is described. Features 13±1 nm high and having a full-width at half maximum of 80±10 nm are fabricated in a square array with lattice constant 212.78 nm, determined by the laser wavelength. The array covers an area of approximately 100 μm×200 μm. Issues associated with laser-focusing of atoms in a two-dimensional standing wave are discussed, and potential applications and improvements of the process are mentioned.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 52 (1991), S. 281-289 
    ISSN: 1432-0649
    Keywords: 42.65.Ky
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the observation of several six-wave mixing processes which result in broadly tunable coherent emission in the wavelength range 1.20–1.45 μm. These emissions are produced in potassium vapor which is simultaneously pumped by two pulsed dye lasers. One set of processes is produced when the frequency of the first laser is fixed to the potassium 4S»6S two-photon transition frequency, while the frequency of the second laser is tuned. The second set of processes is observed when both lasers are tuned, but with their sum frequency fixed to the 4S»6S two-photon transition. Peak output energies of ∼10 nJ/pulse have been observed.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 9 (1988), S. 263-264 
    ISSN: 1434-6079
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We measured the absolute photo-emission cross section of the BC ℓ A → X system around 2720 Å produced by electron-impact dissociation of BCℓ3. The cross section reaches a maximum around 40 eV with a value of 2.5±0.5 × 10−18 cm2. A double-onset structure with onsets around 14 eV and 26 eV indicates that the excited BCℓ fragments are produced via two different dissociation channels.
    Type of Medium: Electronic Resource
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