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Силвия Георгиева
Силвия Георгиева

Atomic And Molecular Spectra Laser By Rajkumar Pdf 56


The plasmonic grating acts as a reflective substrate and a light coupling device to generate more heat than a flat silver substrate under laser photothermal heating (Figure 4). The heating rate of Al NPs with 808 nm laser is enhanced from the plasmonic coupling, which falls within the broad Al absorption spectrum. Absorption spectra consist of the combination of plasmon resonance and interband transitions [73,74]. The 808 nm near-IR laser overlaps with a portion of Al absorption spectra associated with the dielectric loss [72]. The interband transitions of bulk aluminum have an intrinsic peak at 810 nm and the peak intensity grows with increasing particle diameters [75]. Below 600 nm, Al NPs can exhibit dipole, quadrupole, and octupole plasmonic resonances, of which peak wavelengths are red-shifted as the diameter increases [76]. The better confinement of light at these lower wavelengths leads to higher absorption such that the 808 nm wavelength exhibits a relatively weak plasmonic coupling compared to other laser wavelengths. For instance, 446 nm blue and 632 nm red lasers have been utilized as a heating source for Al NP and show a greater electromagnetic coupling due to higher plasmonic absorption, rather than its dielectric loss [10]. The effect of the plasmonic heating leads to heating of the grating, which is undesirable for thermometry purposes. The use of the 808 nm laser was beneficial due to the drastically diminished heating of the grating substrate.

In [6, 7], laser-induced pyrolysis was used for determination of oil shale characteristics. Directing a number of laser shots with high repetition rate to the same spot of the sample under an argon purge, the changes in the spectral line intensities in LIBS spectra over the course of measurements were related to H/C ratios determined on isolated kerogens from the rock samples. Predicted kerogen H/C ratios from the LIBS measurements of whole rock samples were well correlated () to values determined for kerogen isolates measured by elemental analysis [6]. An important advantage of the method is that the decay of intensities of H and C lines with the growth of laser shot number allowed a clear separation of H and C in the organic part of oil shale from that in the inorganic part. However, it is not realistic to apply the above-described laser-induced pyrolysis method for online monitoring of raw material on a running belt.

The HF molecule is a key tracer of molecular hydrogen in diffuse interstellar medium (ISM). Accurate modelling of the HF abundance in such media requires one to model its excitation by both radiation and collisions. In diffuse ISM, the dominant collisional partners are atomic and molecular hydrogen. We report quantum time-independent calculations of collisional cross-sections and rate coefficients for the rotational excitation of HF by H. The reactive hydrogen exchange channels are taken into account in the scattering calculations. For the first time, HF-H rate coefficients are provided for temperature ranging from 10 to 500 K. The strongest collision-induced rotational HF transitions are those with Δj = 1, and the order of magnitude of the new HF-H rate coefficients is similar to that of the HF-H2 ones previously computed. As a first application, we simulate the excitation of HF by both H and H2 in typical diffuse ISM. We show that, depending on the rotational transition, hydrogen atoms increase or decrease the simulated excitation temperatures compared to collisional excitation only due to H2 molecules. Such results suggest that the new HF-H collisional data have to be used for properly modelling the abundance of HF in diffuse ISM. 1e1e36bf2d

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