Synergistic Effects in a ZnO Powder-Based Coating Sequentially Irradiated with Protons, Electrons, and Solar Spectrum Quanta

The authors investigated the changes in diffuse reflectance spectra (ρλ) within 0.32–2.1 μm and integral absorption coefficient (as) of solar irradiation for a zinc oxide powder-based coating. The latter was consequently irradiated with protons (E = 3 keV, F ≤ 1 × 1016 cm−2), solar spectrum quanta (5 eq. of solar irradiation, 1 h), electrons (E = 30 keV, F = 1 × 1016 cm−2), and—repetitively—solar spectrum quanta (5 eq. of solar irradiation, 1 h). Following the irradiation procedure, the decrease in absorption coefficient varied from 0.044 to 0.036 and from 0.062 to 0.04, respectively. Additionally, it was shown that the solar spectrum quanta did not significantly affect the coating pre-irradiated with protons or electrons and did not change the value of induced absorption in the visible region (the latter being caused by the absorption of intrinsic point defects of the zinc oxide crystal lattice). The absorption coefficient degradation decreased under solar spectrum quanta irradiation, which was determined by the decrease in the concentration of free electrons that absorbed in the near-infrared (near-IR) region. ρλ spectra were measured in high vacuum in situ. A post-irradiation transfer of a coating into the atmosphere leads not only to the complete recovery of its reflectance, but also to partial translucence in comparison with the non-irradiated state.

Laser management for congenital dermal melanocytosis

Congenital dermal melanocytosis (CDM) is a malformation of the dermis caused by antenatal impairment of melanogenesis. There are considered data on the epidemiology, history of the study, the characteristics of the pathogenesis and clinical picture of CDM. Data on the efficacy and side effects of treatment of CDM with ruby, alexandrite and neodymium laser in children and adults are compared. The effectiveness of laser treatment for CDM is closely related to the value of the integral absorption of radiation by targeted photothermophores of the epidermis and dermis: melanin, oxyhemoglobin and reduced hemoglobin. The safety of laser exposure is determined by its selectivity, which directly depends on the ratio between the absorption of radiation by the main target photothermophores and water. For the first time, integral indices of the absorption of laser radiation in the pathological focus area by the main photothermophores of the epidermis and dermis (oxyhemoglobin, reduced hemoglobin, as well as the melanin content and localization of ectopic melanocytes in the reticular layer of the dermis) and water are presented. In the CDM involved area, the integrated coefficients of absorption by the main target photothermophores of radiation with a wavelength of 511 nm and 578 nm were shown to be much higher, and the absorption by water is much lower than for radiation with a wavelength of more than 600 nm generated by a ruby, alexandrite or neodymium laser. The described pathogenetic features of laser skin biophotonics upon exposure of the CDM region to the radiation with a wavelength of more than 600 nm increases the risk of the development of such characteristic side effects as hyperpigmentation, deterioration of the collagen structure of the dermis with subsequent formation of scars in the postradiated area. To ensure the complete elimination of ectopic melanocytes and minimize the risk of side effects during laser surgical treatment of CMD area, it is advisable to use the two-wavelengths radiation generated by the copper vapor laser: with a wavelength that is maximally absorbed by melanin (511 nm) and with a wavelength with high absorption of both oxyhemoglobin and hemoglobin (578 nm), but with negligible absorption by water.

Электрон-фононное взаимодействие центров окраски с бесфононной линией 436.55 nm в кристаллах LiF-O, OH

Absorption spectra were recorded at 7.2–300 K at a LiF-O, OH crystal irradiated and UV. The coupling force (S) with the phonons of the lattice of an electron-vibrational transition with a zero-phonon line of 436.55 nm was determined from the ratio of the intensities in the zero-phonon line and the integral absorption band. The nature of the color center responsible for the absorption band at 390 nm and emission 490 nm is determined from the value of S.

Luminescence in lanthanum-gallium tantalate

The optical and luminescent properties of undoped La3Ga5.5Ta0.5O14 lanthanum- gallium tantalate crystals grown in different atmospheres of pure argon gas and argon gas with different oxygen percentages have been studied. The optical absorption α(λ) spectra that characterize integral absorption and reflection have been measured in the 250–700 nm region. The spectral absorption functions have been calculated from the measured α(λ) spectra using the Kubelka–Munk formula. Luminescence has been observed in all the test specimens over a wide spectral region (375 to 650 nm) at 95 and 300 K. The luminescence spectra of the test crystals have a fine dispersed pattern represented by low-intensity discrete luminescence peaks. The 95 K luminescence peak maxima are more pronounced and shifted towards shorter wavelengths by ~16 nm (~0.1 eV) relative to the respective room temperature peaks. The crystal growth atmosphere has been demonstrated to largely affect the luminescent properties of the crystals: the higher the oxygen concentration in the growth atmosphere, the lower the luminescence intensity due to concentration quenching, the luminescence peak maxima shifting towards longer wavelengths. The positions of discrete luminescence peaks have been shown to correlate with the main 420 and 480 nm absorption bands with the respective ~20 nm (~0.2 eV) Stokes shift for crystals grown in different atmospheres. The luminescence in lanthanum-gallium tantalate crystals is a complex process involving several luminescence mechanisms.

Metrological Providing for Infra-Red Detector of Hydrocarbon Emissions in Atmosphere

Results of infra-red (IR) detector calibration on one homolog of oil saturated hydrocarbons are received. Absorption cross-section amount of this homolog is close to average absorption cross-section of saturated hydrocarbons molecules for oil of various fields. Experimental check of such approach acceptability was validated on integral absorption cross-section of n-hexane molecule. It is shown that the offered method of IR detector calibration on one component is admissible for total loss measurement of oil light fractions within the established error of 25%.

Characterization of Microcrystalline Transition from Amorphous Silicon as a Function of Hydrogen Dilution and Substrate Temperature of Hot-wire CVD

Abstracta-Si:H films were prepared by hot wire chemical vapor deposition. One group was deposited at a substrate temperature of Ts=250°C with varied hydrogen-dilution ratio, 0<R<10; the other group was deposited with fixed R=3 but a varied Ts from 150 to 550°C. IR, Raman and PL spectra were studied. The Raman results indicate that there is a threshold value for the microstructure transition from a- to μc-Si. The threshold is found to be R ≈ 2 at Ts = 250°C and Ts ≈ 200°C at R=3. The IR absorption of Si-H at 640 cm-1 was used to calculate the hydrogen content, CH. CH decreased monotonically when either R or Ts increased. The Si-H stretching mode contains two peaks at 2000 and 2090 cm-1. The ratio of the integral absorption peaks I2090/(I2090+I2090) showed a sudden increase at the threshold of microcrystallinity. At the same threshold, the PL features also indicate a sudden change from a- to μc-Si., i.e. the low energy PL band becomes dominant and the PL total intensity decreases. We attribute the above IR and PL changes to the contribution of microcrystallinity, especially the c-Si gain-boundaries.