Photoluminescence spectra of various samples made of polymethyl methacrylate (PMMA) induced by 222-nm-wavelength radiation of a KrCl excilamp with a bandwidth of ~ 2 nm and a narrow-band KrCl laser, as well as transmission spectra of these samples, have been investigated. It was found that the PMMA samples, according to their transmission spectra, can be divided into three characteristic groups with different short-wavelength transmission edges, which affect the photoluminescence spectra. It has been shown that the photoluminescence spectra of PMMA samples in the ultraviolet and visible regions depend on the power density of the exciting radiation.
The study of exciton cathodoluminescence in diamond is not only scientific but also practical importance. Ultraviolet radiation at a wavelength of 235 nm can be used for disinfection, activation of surface reactions, photochemistry, and more. Thus, diamond is a promising material for creating a cathodoluminescent source of ultraviolet radiation. We have investigated the temperature dependences of the exciton cathodoluminescence spectra of single-crystal diamond in the temperature range from 80 to 400 K. The temperature dependences showed a characteristic increase in the intensity of exciton cathodoluminescence in the range 230-240 nm with increasing temperatures from 80 K to 150- 180 K. Further increase in temperature to room temperature (297 K) leads to a twofold decrease in the radiation intensity. With a further increase in temperature to 400 K, no change in the cathodoluminescence intensity was observed within the error
Experimental study and theoretical analysis of growth of microstructures (microtowers) on liquid metals by fs laser pulses have been carried out. Theoretical analysis has been performed on the basis of the two-temperature model. Compared to ns laser pulses, in fs irradiation regimes the heat-affected zone is strongly localized resulting in much larger temperatures and temperature gradients. In the experimental irradiation regimes, the surface temperature of liquid metals studied may reach or even exceed a critical level that culminates in phase explosion or direct atomization of a metal surface layer. However, before explosive ablation starts, a stress wave with an amplitude up to several GPa is formed which demolishes oxide covering. Moreover, at high laser fluences laser-induced breakdown is developed in oxide layer covering the metal surface that leads to destruction/ablation of oxide without damaging metal underneath. An overall scenario of microstructure growth with fs laser pulses is similar to that obtained for ns irradiation regimes though the growth threshold is lower due to smaller heat-conduction losses. Also we managed to obtain microstructures formation by the action of spark discharge.
Nowadays the sources of long-wavelength optical radiation (far infrared, terahertz range) are developed intensively. They have good perspectives in different fields of biology, medicine, security systems etc. This implies the need to have the detectors of radiation with advanced parameters 1,2. Golay cell 3 is one of the most sensitive detector types available at the time being despite, the strong development of semiconductor detectors 4 – 6. In Golay cell the energy is measured by the expansion of the gas in the sealed chamber: the gas absorbs the energy and presses the flexible membrane, thus the change of volume is registered. The disadvantages of these detectors are relatively high price, big size and vibration susceptibility. In our paper we consider the method of radiation detecting that is similar to one that is used in Golay cell but based on gas temperature measurement.
Integrated photoluminescence spectra of two diamond samples under laser radiation excitation at 193 and 222 nm, depending on the temperature in the range of 80-300 K and the peak intensity in the range of 7-13 MW/cm2, were investigated. At temperatures below 200 K, and the peak intensity of more than 10 MW/cm2 of laser radiation at 222 nm, the radiative recombination band of electron-hole liquid was observed in integrated photoluminescence spectra of CVD diamond sample.
In our work we investigated different optical characteristics of five diamond samples that were supposed to be pure. The characteristics were the following: optical absorption spectra in the range 200 nm – 15μm, Raman scattering spectra in the range 100-3700 cm-1 and photoluminescence spectra in the range 200 – 850 nm. The temperature of diamond samples was varied from 80 to 300 K. Photoluminescence was excited by KrCl*-laser radiation (λ=222 nm) with pulsewidth of 8 ns (FWHM) and peak intensity of 13 MW/cm2. We found out that the band of radiative recombination of the electron-hole liquid (with the maximum at 240 nm) can be observed in the photoluminescence spectra if the absorption coefficient of the diamond sample is less than 10 cm-1 in the range 225-226 nm.
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