The a-, σ- and π-spectra of quartz in the IR regions were measured under FTIR spectroscopy, and overtone and combination modes perpendicular to the c-axis of quartz were confirmed to be electric vector active by the coincidence of the a-spectrum with the σ-spectrum among the three kinds of spectra. Absorption coefficients of overtone and combination modes intrinsic to the a- σ-, and п-spectra of quartz were measured. The thickness of quartz thin sections can be determined by applying the absorption coefficients obtained from the α- and σ-spectra to the polarized IR absorption spectra measured under E ⊥ the c-axis.

Absorption coefficient (k), infinite reflectance (Ri), and scattering coefficient (s) were tabulated for five wavelengths and analyzed for statistical differences for seven weed species. The wavelengths were: 0.55 μm, 0.65 μm, 0.85 μm, 1.65 μm, and 2.20 μm. The Ri of common lambsquarters (Chenopodium album L.), johnsongrass [Sorghum halepense (L.) Pers.], and annual sowthistle (Sonchus oleraceus L.) leaves at the 0.85-μm wavelength were significantly (p = 0.05) higher than for sunflower (Helianthus annuus L.), ragweed parthenium (Parthenium hysterophorus L.), or London rocket (Sisymbrium irio L.). Annual sowthistle had the largest k value, and Palmer amaranth (Amaranthus palmeri S. Wats.) had the smallest k value at the 0.65-μm chlorophyll absorption wavelength. In general, johnsongrass, ragweed parthenium, or London rocket had the largest s values among the five wavelengths, whereas annual sowthistle and Palmer amaranth were usually lowest.

Understanding the radiation model of a flash lamp is essential for the reflector design of a laser amplifier. Reflector design often involves several simplifying assumptions, like a point or Lambertian source; either of these assumptions may lead to significant errors in the output distribution. In practice, source non-idealities usually result in sacrificing the amplifier’s gain coefficient. We propose a novel test technique for attaining the xenon flash lamp absolute spectral intensity at various angles of view, and then accurately predict radiation distributions and generate the reflector shape. It is shown that due to the absorption of emitted radiation by the lamp itself, the behavior of the radiation model at various wavelengths is different. Numerical results of xenon plasma absorption coefficient were compared with the measured data. A reasonable agreement was obtained for the absorption coefficient parameters. Thus, this work provides a useful analytical tool for the engineering design of laser amplifier reflectors using xenon flash lamps as pumps.

In this paper, we designed an experiment to research the properties for the stimulated Brillouin scattering (SBS) medium of perfluorocarbon-compounds (PFCs) and perfluoropolyether (PFPE), then we proposed that the selection principle of the high load capacity SBS medium can be used in the high peak power SBS system. The results showed that, for PFCs, perfluorinated hydrocarbons (FC-72) has the highest optical breakdown threshold (OBT); for PFPE, the medium with average molecular weight (AMW) less than 1000 has small medium absorption coefficient (AC) and high OBT, for AMW, greater than 1000, the medium AC becomes high and the OBT becomes low. Further research shows that, for PFPE series SBS medium, the AC increases and the OBT decreases gradually with increasing of AMW. We find some SBS mediums can work stably under high peak power pump, which lays a good foundation for the application of SBS technology in a high-power laser system.

An improved two-temperature model to describe femtosecond laser ablation of metal target was presented. The temperature-dependent heat capacity and thermal conductivity of the electron, as well as electron temperature-dependent absorption coefficient and absorptivity are all considered in this two-temperature model. The tailored two-temperature model is solved using a finite difference method for copper target. The time-dependence of lattice and electron temperature of the surface for different laser fluence are performed, respectively. The temperature distribution of the electron and lattice along with space and time for a certain laser fluence is also presented. Moreover, the variation of ablation rate per pulse with laser fluence is obtained. The satisfactory agreement between our numerical results and experimental data indicates that the temperature dependence of heat capacity, thermal conductivity, absorption coefficient and absorptivity in femtosecond laser ablation of metal target must not be neglected. The present model will be helpful for the further experimental investigation of application of the femtosecond laser.

Patterns of absorption and reflection of an ultrashort laser pulse by plasma with a solid-state density, which are realized in the mode of the normal skin effect, are studied. If the pulse power is so high to provide the electron heating during the time shorter than the reciprocal fundamental frequency, a nonlinear suppression of absorption takes place and the spectrum of the reflected radiation contains odd harmonics of the fundamental frequency.

Nitrogen (N) and phosphorus (P) limitation affect the photosynthetic apparatus of Dunaliella tertiolecta in markedly different ways. When grown at 0·25 d−1 (18 % of the resource-saturated maximum rate, μmax=1·39 d−1) in chemostat cultures, N- and P-limited cells were chlorotic relative to nutrient-replete controls. The lutein-to-chlorophyll a ratio increased under both N and P limitation, whereas the neoxanthin-to-chlorophyll a ratio increased only under P limitation. The ratio of accessory photoprotective pigments (α- and β-carotene) to chlorophyll a increased under N-limited conditions. Despite differences in accessory pigment complement, chlorophyll a-specific light absorption coefficients of N- and P-limited cultures did not differ significantly, and were greater than in nutrient-replete conditions. In contrast, the initial slope of the photosynthesis–irradiance (PE) response curve (αChl) declined under nutrient-limiting conditions. There were slight reductions in the maximum quantum efficiency of photosynthesis (ϕm) in N- and P-limited cells. Reductions in ϕm were accompanied by reductions in the ratio of variable to maximum fluorescence (Fv/Fm), and the ratio of the photosystem II reaction centre protein D1 to the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco). Differences in light-saturated gross photosynthesis rate, as measured by light/dark oxygen exchange, could be accounted for by changes in the abundance of the carboxylating enzyme Rubisco. Oxygen exchange and 14CO2 assimilation appeared to measure different processes in P-limited and N- limited cultures. At light-saturation, 14C-bicarbonate assimilation approximated gross photosynthesis (as measured by light/dark oxygen exchange) in P-limited cultures. In contrast, 14C-bicarbonate assimilation approximated net photosynthesis in N-limited cultures. When all culture conditions were compared, there was linear covariation of the rates of reductant supply via light absorption and photochemical charge separation with the rates of reductant demand for CO2 fixation and NO3− reduction.