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Phase-selective growth of VO2 and V2O5 nanowires was realized via catalyst-free physical vapor deposition from bulk VO2 powder. Single nanowire Raman spectroscopy was used to analyze the distribution of the vanadium oxide phases within the reactor. VO2 (V2O5) nanowires were identified by characteristic peaks at 197, 224, and 620 cm-1 (149, 700, and 994 cm-1). Electron diffraction and polarization-dependent Raman spectra indicated that the growth directions of VO2 and V2O5 nanowires were [100] and [010]. Analysis of Raman spectra in two polarization configurations is sufficient to distinguish between low-index nanowire growth directions for the V2O5 phase. Single nanostructure Raman measurements thus provide a means to rapidly analyze the phase and growth direction of anisotropic nanostructures. [ABSTRACT FROM AUTHOR]

Quenching of highly excited vibrational states of NO2 in baths of CO2, N2O, and CO has been investigated. Dilute NO2 mixtures were excited by a pulse from an excimer pumped dye laser operating at 495 nm. The ν3 antisymmetric stretching modes of CO2 (2349 cm-1) and N2O (2223 cm-1) and the v=1 level of CO (2143 cm-1) were probed with continuous wave IR diode lasers. The amount of energy transferred from excited NO2 to the ν3 modes of both CO2 and N2O was found to be 3%±1% of the original excitation energy. On the other hand, a smaller amount of energy (0.9%±0.3%) was deposited into the CO vibrational mode for NO2 contained in a dilute CO bath. These results support a picture of very inefficient transfer from high energy states of donor molecules to the high-frequency vibrational modes of small bath molecules. Differences in the efficiency of energy reception by the high-frequency modes of these three molecules scale roughly as the infrared transition moments for the bath states indicating the importance of resonance effects in the energy transfer process, but a combination of short- and long-range force mechanisms is probably necessary to account for the observed differences. [ABSTRACT FROM AUTHOR]

A configuration of a ring-type bluff body situated in a circular pipe is suggested as a design of a vortex flowmeter. Experiments were carried out to test a series of ring-type bluff models, whose geometrical parameters are expressed in terms of the gap ratio G/W and the slenderness ratio D/W, where G denotes the gap width between the outer edge of the ring and the pipe wall, W denotes the width of the ring, and D denotes the mean diameter of the ring. Major efforts are focused upon a group of the ring-type vortex shedders whose vortex shedding process is strongly influenced by the presence of the wall. Results obtained suggest the appropriate sizes of rings for which the vortex shedding frequency can be clearly measured either on the pipe wall or at the center of the pipe. [ABSTRACT FROM AUTHOR]