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  • 82  (4)
  • 79.20.Ds  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Nonlinear laser UV photochemistry of maleic acid in aqueous solution (1983)
    Springer
    Applied physics 31 (1983), S. 145-151 
    Details
    ISSN: 1432-0649
    Keywords: 82 ; 87
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This work deals with photochemical transformations of maleic acid in an aqueous solution under powerful picosecond fourth-harmonic pulses of a YAG-Nd3+ laser with λ=266 nm and nanosecond pulses of an excimer KrF laser with λ-248 nm. It has been found that by changing the irradiation intensity only it is possible to produce selectively different products with a high quantum yield resulting from the following reactions of the −C=C− bond of the maleic acid molecule: 1) cis-trans isomerization at radiation intensities up to 108 W/cm2 as a result of linear photochemistry; 2) radical dimerization of the maleic acid withJ=108÷109 W/cm2 and water addition to the −C=C− bond of the maleic acid withJ≃109 W/cm2 as a result of nonlinear photochemistry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00688835
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  • 2
    Electronic Resource
    Electronic Resource
    Laser-stimulated field desorption of molecular ions from a tungsten emitter (1988)
    Springer
    Applied physics 45 (1988), S. 53-57 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00692342
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  • 3
    Electronic Resource
    Electronic Resource
    Time-resolved laser optoacoustic tomography of inhomogeneous media (1996)
    Springer
    Applied physics 63 (1996), S. 545-563 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01830994
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  • 4
    Electronic Resource
    Electronic Resource
    Laser ablation of aqueous solutions with spatially homogeneous and heterogeneous absorption (1994)
    Springer
    Applied physics 59 (1994), S. 73-81 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01081730
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  • 5
    Electronic Resource
    Electronic Resource
    UV picosecond laser-induced formation of amino acids from aqueous solutions of ammonic salts of dicarboxylic acids (1981)
    Springer
    Applied physics 26 (1981), S. 243-245 
    Details
    ISSN: 1432-0649
    Keywords: 82 ; 87
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It is shown for the first time that the irradiation of the ammonic-salt aqueous solutions of the dicarboxylic acids by powerful ultrashort uv pulses provokes the formation of the related amino acids. The amino-acid quantum yield depends on the intensity and for the aspartic acid, in particular, it reaches 40% at the intensity of about 1 GW/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00692545
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  • 6
    Electronic Resource
    Electronic Resource
    Photoionization mass-spectrometry of benzene and benzaldehyde molecules with an excimer KrF laser (1980)
    Springer
    Applied physics 22 (1980), S. 293-297 
    Details
    ISSN: 1432-0630
    Keywords: 33 ; 82 ; 50
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A laser photoionization time-of-flight mass-spectrometer has been developed and used to investigate the photoionization and photofragmentation of benzene and benzaldehyde molecules by an excimer KrF laser radiation at the wavelength of 249 nm in the intensity range from 5·104 to 5·109 W/cm2. It has been found that at low laser intensity ions formed by two-step photoionization are most abundant in mass spectra. By increasing laser intensity an extensive fragmentation of molecules, up to C+ ions, was observed. The maximum ionization yield of benzaldehyde comes to 0.1% of the number of molecules in the photoionization volume and, according to calculations, to 10% for benzene molecules, when the radiation intensity is 5·109 W/cm2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899880
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  • 7
    Electronic Resource
    Electronic Resource
    High quantum yield of photochemical reactions of protoporphyrin-IX induced by powerful ultrashort laser pulses (1981)
    Springer
    Applied physics 24 (1981), S. 245-247 
    Details
    ISSN: 1432-0630
    Keywords: 82 ; 87
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The action of powerful pulsed picosecond radiation from a Nd: YAG laser (λ=530 nm, pulse energy: 0.01 J, intensity: 2GW/cm2) and an argon laser (λ=515 nm, power: 50 mW) on protoporphyrin-IX dimethylether in three solvents (trichlormethane, carbon tetrachloride, dioxane) has been studied. Under continuous irradiation the quantum yield and resulting products do not differ materially from the ones produced under mercury lamp irradiation. When irradiation is performed by powerful laser pulses of picosecond duration the quantum yield of photodecomposition of protoporphyrin-IX dimethylether inereases substantially: by 10 in dioxane, by 4 in carbon tetrachloride and by 100 in trichlormethane. It is assumed that a quite different mechanism of multistep excitation is responsible for photodecomposition under powerful picosecond pulses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00899765
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