Estimation of Vibrational Temperatures of N-2 and CO2 in Low-Pressure Electron Cyclotron Resonance Plasmas by Threshold Ionization Mass Spectrometry

This paper demonstrates the estimation of vibrational temperatures of N-2 and CO2 in low-pressure plasmas by threshold ionization mass spectrometry. The principle for the estimation is the decrease in the ionization potential by the vibrational excitation. We observed that the threshold ionization curves of N-2 and CO2, which were measured using a quadrupole mass spectrometer with an energy-variable electron beam, shifted toward the low-energy side, when they were sampled from the plasmas. We constructed a model which assumed a Boltzmann distribution for the population densities of vibrational excited states and the same cross sections of electron impact ionization for vibrational excited states except the shifts of the threshold energies. The vibrational temperatures were estimated by fitting the experimental threshold ionization curves with the model

In situ FT-IR study on the homogeneous nucleation of nanoparticles of titanium oxides from highly supersaturated vapor

The formation of nanoparticles of titanium oxides by homogeneous nucleation from highly supersaturated vapors was investigated by in situ Fourier transform IR spectroscopy and by observation of the resulting nanoparticles by transmission electron microscopy (TEM). Titanium metal was thermally evaporated in a specially designed chamber under a gaseous atmosphere of oxygen and argon. Nano particles nucleated and subsequently grew as they flew freely through the oxidizing gas atmosphere. Nascent nanoparticles of titanium oxides showed a broad IR absorption band at 10-20 mu m. Subsequently, the cooled nanoparticles showed a sharp crystalline anatase feature at 12.8 mu m. TEM observations showed the formation of spherical anatase nanoparticles. The IR spectral evolution showed that the titanium oxides nucleated as metastable liquid droplets, and that crystallization proceeded through secondary nucleation from the supercooled liquid droplets. This suggests that history of the titanium oxide nanoparticles, such as the temperature and oxidation that they experience after nucleation, determines their polymorphic form. (C) 2016 Elsevier B.V. All rights reserved

Isotope ratios of 240Pu/239Pu in soil samples from different areas

International Symposium on Transfer of Radionuclides in Biosphere-Prediction and Assessment

Isotope ratios of 240Pu/239Pu in soil samples from different areas.

International Symposium on Transfer of Radionuclides in Biosphere-Prediction and Assessment

Distribution of nuclear bomb Pu in Nishiyama area, Nagasaki, estimated by accurate and precise determination of Pu-240/Pu-239 ratio in soils

The 2nd International Conference on Radioactivity in the Environment & The 6th International conference on environmental radioactivity in the Arctic and the Antarcti

Distribution of nuclear bomb Pu in Nishiyama area, Nagasaki, estimated by accurate and precise determination of Pu-240/Pu-239 ratio in soils

The 2nd International Conference on Radioactivity in the Environment & The 6th International conference on environmental radioactivity in the Arctic and the Antarcti

Self-assembly of MoO3 needles in gas current for cubic formation pathway

Nucleation and subsequent rapid growth are enigmatic due to the unrevealed pathways. Despite the relatively simpler mechanism compared to nucleation and growth in solution, that in vapor has received little attention. The largest hindrance to unveiling this process may be observing the rapid and mesoscopic-scale phenomena. To overcome this hindrance, we combine an experimental approach with in situ spatial scanning Fourier-transform infrared spectroscopy, which reveals the nucleating and growing nanoparticles in vapor. The nanoparticles are then collected at different evolutionary stages and analyzed by ex situ transmission electron microscopy (TEM). Needle-shaped molybdenum oxide (MoO3) nanoparticles were formed within similar to 0.1 s after homogeneous nucleation from a highly supersaturated vapor. Over one second, the needle particles gradually evolved into a cubic shape by fusion in a crystallographically favored orientation in a free-flying state in vapor. The similar sizes of the elongated axes of the needle and cubic structures suggest an additional growth stage, in which the needle particles become the growth units of the cubic particles. The morphology of a final crystal should reflect the formation environment of the particle because growing crystals are sensitive to the formation conditions such as temperature, concentration, and impurities. Although nucleation under very high supersaturation induces the anisotropic growth of the needle particles, this information of the initial nucleation environment is lost in the final cubic crystal. These findings enrich our understanding of pathways in the nucleation and growth of nanoparticles and provide new insights into the growth stages driven by oriented attachment