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  • 79.20.Ds  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 45 (1988), S. 53-57 
    ISSN: 1432-0649
    Keywords: 33 ; 79.20.Ds ; 79.70.+q
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report here on a experimental observation of photon-stimulated field emission of molecular anthracene ions from the surface of a layer adsorbed on a tungsten field-emitter tip. When the tip is irradiated with laser pulses 249, 308, and 400 nm in wavelength falling within the absorption bands of anthracene, the stimulated ion signal is proportional to the pulse fluence. The efficiency of the process decreases with the increasing laser wavelength. Photon stimulation is believed to be due to the resonance excitation of the anthracene molecules, followed by the field ionization of the excited molecules.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 63 (1996), S. 545-563 
    ISSN: 1432-0649
    Keywords: 79.20.Ds ; 87.71.Rh ; 87.73.Ca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The methods of time-resolved laser optoacoustic tomography of inhomogeneous media and related problems are reviewed. Time-resolved laser optoacoustic tomography allows one to measure the distribution of light absorption in turbid media with depth resolution up to several microns in real time. The theory of laser excitation of acoustic waves by absorbing of light in particles, dispersed in transparent, light-absorbing or scattering media, is developed. The distribution of light absorption can be obtained from the temporal course of acoustic pressure. Two schemes of acoustic wave detection — in the medium under testing (direct detection) and in transparent medium, coupled to the investigated one (indirect detection) — are discussed. In both cases the reconstruction of light absorption can be made by simple calculations. Test experiments with homogeneous and layered media confirm the proposed theoretical models and the possibility of using the proposed experimental schemes. Light absorption in homogeneous, inhomogeneous media and in absorbing particles dispersed in turbid media was investigated. The experimental setup allows one to measure the absorption coefficients over the range 1-500 cm−1 with the depth resolution 10–15 μm over the depth 1–1.5 mm.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0649
    Keywords: 79.20.Ds ; 83.70.Hq ; 83.70.Gp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The ablation efficiency of aqueous solutions with different concentrations and spatially homogeneous (CuCl2 solution) and heterogeneous (ink solution) absorption was studied as a function of the pulse-energy fluence (Nd:YAG laser, λ=1064 nm, τp = 20 ns). The latter was varied over a wide range from 0.15 J/cm2 to 8.00 J/cm2. The ablation threshold of solutions with heterogeneous absorption was found to be much lower (3 to 4 times) than the ablation threshold of solutions with homogeneous absorption and with the same average absorption coefficient. The ablation efficiency of heterogeneous solutions was higher by more than an order of magnitude. It was found that the ablation efficiency increases drastically for both types of solutions as the pulse energy fluence was raised to exceed the ablation threshold by 2 or 3 times. At such energy fluences, along with small droplets, larger droplets (1.5–2 mm cross section) could be ejected. This points to the ablation of solutions being affected by a hydrodynamic shock formed as a result of the pulsed recoil pressure excerted by the ablation products. The differences between the ablation processes for solutions with homogeneous and heterogeneous absorption as well as the hydrodynamic destruction at high energy fluences are discussed.
    Type of Medium: Electronic Resource
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