Dynamics of the emission spectrum of a highly focused femtosecond laser pulse under filamentation in air have been investigated. A peak at 735 nm and a drop in the laser-beam intensity at the ...fundamental wavelength are observed in the spectrum of a laser pulse passed through the filamentation zone. It is shown that the peak is likely due to the Rabi splitting of the O I levels and breaking of the
LS
coupling for the 3
p
5
P
level in a strong laser field.
—
We have obtained limits of detection (LoD) of Al (396.15 nm), Ba (553.35 nm), Ca (422.67 nm), Mg (285.21 nm), Na (588.99 nm) and Mn (403.08 nm) in liquid-droplet aerosol by filament-induced ...spectroscopy (R-FIBS) using ultrashort laser pulses (60 fs, 800 nm, 4.4 mJ). The limit of detection of the Na by emission line (588.99 nm) in a liquid-droplet aerosol was obtained by laser induced breakdown spectroscopy (LIBS) using short laser pulses (7 ns, 1064 nm, 550 mJ). The obtained results were compared within the framework of the methods used.
—
The dependence of the limits of detection of Mg, Mn, Sr, Pb, Al, and B in aqueous solutions on the laser pulse repetition rate is studied by femtosecond laser induced breakdown spectroscopy for the ...laser pulse repetition rate from 50 to 1000 Hz. The limit of detection is shown to be the best at a laser pulse repetition rate of 166 Hz for all the elements under study, other experimental conditions being the same.
The dependence of the intensity of Ca (393.3, 396.8, 422.6 nm), Mg (383.6 nm), and Na (589 nm) emission lines on the laser pulse duration in the method of filament-induced breakdown spectroscopy is ...studied. A filament was excited in seawater aerosol droplets 0.8–2 μm in size by laser pulses of 70, 230, 500, and 900 fs duration at a constant pulse energy of 3.0 mJ. The intensities of the emission lines of the elements under study are shown to increase with the laser pulse duration, except for the magnesium line. Optimal laser pulse durations for the excitation of Ca, Mg, and Na lines in seawater aerosol are derived.
The capabilities of filament-induced breakdown spectroscopy for the analysis of the elemental composition of aqueous aerosols were estimated. The diameter of aqueous aerosol droplets in the ...atmosphere was 0.8–2.0 μm. The emission lines of the chemical elements were excited by fi lamentation of femtosecond laser pulses (60 fs, 800 nm, 4.4 mJ) in weak focusing mode by a lens with a focal length of 500 mm. The obtained limits of detection for Al (396.15 nm), Ba (553.35 nm), Ca (422.67 nm), Mg (285.21 nm), Na (588.99 nm), and Mn (403.08 nm) in an aqueous aerosol were 12.1, 41.7, 10.0, 7.3, 0.7, and 32.3 mg/L, respectively.
The spectral characteristics of plasma generated on the surface of human hairs under various focusing conditions (lenses with focal lengths 50, 100, and 150 mm) by short (9 ns) laser pulses with ...energies from 50 to 50 mJ were experimentally studied by elemental analysis along the length of the samples. The minimal energies of the laser pulses were obtained. The optimal conditions for recording emission lines of magnesium and calcium in the studied samples were determined.
Lake Baikal is inhabited by a relatively large number of cyclopid species, many of which are endemics. Two genera,
Diacyclops
Kiefer, 1927 and
Acanthocyclops
Kiefer, 1927, are the most specious in ...the lake. Taxonomic discrimination of the majority of representatives of these genera is difficult owing to their high morphological similarities and poor standard description. In this study, a molecular phylogenetic analysis of Lake Baikal members of the
Diacyclops/Acanthocyclops
group is performed on the basis of mitochondrial cytochrome c oxidase subunit I (
COI
) gene. It is shown that a fragment of
COI
1000 bp long is sufficient for intragenus discrimination of the cyclopids of Lake Baikal. The issues of
Diacyclops/Acanthocyclops
taxonomy are reflected in the obtained molecular data. Two distinct phylogenetic groups of
Diacyclops
genus with uncertain taxonomic status are revealed.
Experimentally obtained dependences of acoustic signals on the energy of femtosecond pulses propagating in the filamentation mode in a liquid-drop aerosol with nanoparticles of different ...concentrations simulating the aerosol with the Aitken nuclei are presented. It is shown that under the action of a femtosecond pulse filament, a water aerosol jet splits into two parts.
—
Two techniques for multielement analysis of liquid-droplet aerosol are compared, which are based on the spectral analysis of the radiation of a laser plasma generated in a laser breakdown (LIBS) or ...during laser pulse filamentation in a liquid droplet aerosol (R-FIBS). A liquid-droplet aerosol containing Na solution is used. It is shown that there are optimal delay times of the start of signal recording relative to the start of plasma generation, at which the signal-to-noise ratio is maximal, for both techniques. The dependence of the signal-to-noise ratio is derived for different laser radiation focusing deep into a liquid-droplet cloud for LIBS. The Na detection limits are determined for both methods.
Laser technologies that are used for the development of sensor elements for Remotely Operated Vehicles (ROVs) are presented, as well as the latest developments in underwater robotics where laser ...spectroscopy methods are applied to environmental monitoring. A submersible laser spectrometer unit intended for studying Raman scattering and laser-induced fluorescence (LIF) spectra is presented. The spectrometer was developed as an element of an ROV sensor system for remote detection and measurements of organic matter concentrations in sea water and underwater objects. The results of environmental tests of the submersible LIF spectrometer in various marine areas, including the Arctic, are described.
