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1.
Ablation of an optically homogeneous absorbing medium by scattered pulsed laser radiation 总被引:1,自引:0,他引:1
V. V. Golovlyov R. O. Esenaliev V. S. Letokhov 《Applied physics. B, Lasers and optics》1993,57(6):451-457
We have studied the ablation of an aqueous CuCl2 solution in a pulsed Nd:YAG laser field featuring a speckle-patterned structure characterized by spatial radiation energy fluence fluctuations. This leads to a nonuniform distribution of the energy absorbed in the bulk of the sample being irradiated and causes local overheating centers to form, wherein ablation is observed to take place at laser energy fluences below the threshold value found in experiments with a homogeneous laser beam. This effect should be manifest in the laser irradiation of biotissues which, as a rule, scatter light strongly. 相似文献
2.
V. S. Antonov V. S. Letokhov A. N. Shibanov 《Applied Physics A: Materials Science & Processing》1981,25(1):71-76
The paper presents the results of studies into ion desorption from the surface of adenine and anthracene molecular crystals
and anthracene molecules adsorbed on a metal as the surface is irradiated by an uv laser at λ=249, 308, and 337 nm. A sharp
increase in molecular ion yield has been revealed with a decrease in radiation wavelength down to 249 nm. At this wavelength
the effect of molecular ion desorption is observed at the radiation intensity of 20∶50 kW/cm2 and pulse duration of 20 ns, it cannot be explained by thermal mechanisms. The initial velocity distribution of photoions
is nonthermal by character, with maximum velocity of 2·105 cm/s in case of adenine. The mechanisms responsible for the effect observed are discussed. 相似文献
3.
An ir multiphoton dissociation (MPD) process in multiple-frequency ir-laser fields has been experimentally realized. A selectivity ofS=104 was obtained in separating13C/12C isotopes upon multiple-frequency ir multiphoton dissociation (MFMPD) of the CF2HCl molecule, the dissociation yield13 for the13CF2HCl molecule amounting to around 1%. A yield of13 was reached at a selectivity ofS=102, and the total laser fluence required for the process was reduced. A new mechanism—sticking of molecules on the lower discrete vibrational levels—responsible for the low MPD yields observed for some molecules is discussed and a technique to eliminate it and thus maximize the dissociation yields is proposed. Ways to improve the selectivity by MFMPD are analyzed and a simple method for obtaining from a single TEA CO2 laser a multiple-frequency radiation suitable for experimental realization of MFMPD is suggested. 相似文献
4.
The combined “Gas Chromatograph — Laser Optoacoustic Spectrometer” (GC-LOAS) has been used to perform selective analysis of a mixture of fatty acid esters stereocisomers and a mixture of methylcyclopentadiene positional isomers. The GCLOAS system allows simultaneous recording of the retention time of the components in the mixture under analysis and their IR absorption spectra in the spectral operating range of the 12CO2, 13CO2 and HeNe lasers. It has been shown that the hydrogenated sample of fatty acids contains a lot of trans-isomer. Its content has been quantitatively estimated. The identification of methylcyclopentadiene isomers (both monomers and dimers) has been carried out, too. 相似文献
5.
Summary The action spectra of low-intensity light in the range from 300 to 900 nm on the synthesis rate of nucleic acids in the culture
of HeLa cells has been measured. The synthesis of DNA and RNA is stimulated in several spectral intervals with maxima nearby
400, 630, 680, 760 and 820 nm. The stimulation effect is very sensitive to the irradiation duration (light intensity) at a
fixed dose. The dose that causes the maximal stimulation is approximately 10 times smaller in the near-UV blue region than
in red-IR region.
Riassunto Si è misurato lo spettro d’azione della luce a bassa intensità nell’intervallo da 300 a 900 nm sul tasso di sintesi degli acidi nucleici in culture di cellule HeLa. La sintesi di DNA ed RNA è stimolata in parecchi intervalli spetrali con massimi vicino a 400, 630, 680, 760 e 820 nm. L’effetto di stimolazione è molto sensibile alla durata d’irradiazione (intensità della luce) ad una dose fissa. La dose che causa la stimolazione massima è approssimativamente dieci volte piú piccola nella regione blu dell’ultravioletto vicino che nella regione del rosso-infrarosso.
Резюме Измерен спектр действия низкоинтенсивного света в диапазоне (300⋎900) нм на скорость синтеза нуклеиновых кислот в культуре клеток HeLa 1.5 часа после облучения. Синтез ДНК и РНК стимулируется в несколбких спектральных интервалах с максимумами вблизи 400, 630, 680, 760 и 820 нм. Эффект стимуляции очень чувствителен к продолжительности облуения (интенсивности света) при фиксированной дозе. Доза, при которой наблюдается максимальная стимудяция, в несколько ваз меньше в ближнеи УФ-синей области с максимумом около 400 нм.相似文献
6.
Using two-frequency technique for the multiple photon dissociation of OsO4 molecule by IR laser radiation, the following new results have been obtained: 1. the narrow resonances of multiple photon absorption on few low lying vibrational transitions have been found in the dissociation yield as a function of exciting frequency ν1; 2. the structure of the dissociation yield as a function of dissociating frequency ν2 connected with high lying vibrational transition has been studied; 3. the kinetic of the vibration relaxation of high vibrationally excited molecules was investigated; 4. the unimolecular character of the multiple photon dissociation of OsO4 has been proved. 相似文献
7.
G. D. Alkhazov A. E. Barzakh V. P. Denisov V. S. Ivanov I. Y. Chubukov V. N. Fedoseev V. S. Letokhov V. I. Mishin S. K. Sekatsky 《Hyperfine Interactions》1990,61(1-4):1335-1338
New results on spins, electromagnetic moments and isotopic changes of nuclear charge radii for
63
157–159
Eu,
64
146, 148, 150
Cd and
65
147–155, 157, 159
Tb have been obtained from hyperfine structure and isotope shifte measured with laser resonance photoionization technique.
These results complement two-dimensional picture (with respect to H and Z) of the changes of nuclear ground state properties
near the “critical” neutron numbers N=88–90 in the vicinity of the “magric” proten number Z=64. 相似文献
8.
Ambartzumian R. V. Furzikov N. P. Letokhov V. S. Puretsky A. A. 《Applied Physics A: Materials Science & Processing》1976,9(4):335-337
A new method of photoionization cross-section measurement based on the observation of saturation in the ion yield as a function
of radiation intensity has been proposed. The photoionization cross-sections for the 62P1/2 and 62P3/2 levels of Rb atoms of the fundamental and second harmonics of ruby laser radiation are measured, with a tunable pulsed dye
laser used for excitation. The following values of cross-sections are obtained: (1.7±0.4)·10−17 cm2 and (1.5±0.4)·10−17 cm2 for the levels 62P3/2 and 62P1/2, respectively, ionized by radiation of v2=14403 cm−1, and (1.9±0.5)·10−17 cm2 for the 62P3/2 level ionized by v2=28806 cm−1 radiation. 相似文献
9.
Nanolocalized ion packets have been produced due to the transmission of photoions, which are emitted from a refractory metal emitter irradiated by femtosecond laser radiation with a high repetition rate, through a quartz nanocapillary. With the use of such a pulsed nanobeam, a miniature ion microscope has been created and the image of a dielectric-nanoaperture fragment has been obtained. 相似文献
10.
B. N. Mironov S. A. Aseev V. S. Makin S. V. Chekalin V. S. Letokhov 《JETP Letters》2008,88(4):261-263
Extended periodic microstructures are formed on a thin gold film by femtosecond laser radiation. The structure length is an order of magnitude larger than the typical size of the irradiated region. The detection of gold photoions generated in the process of the microstructuring ensures a high-sensitivity on-line diagnostics of this phenomenon. 相似文献