Browsing by Author "Su, Man-Nung"

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Does Ozone-Water Complex Produce Additional OH Radicals in the Atmosphere?
(2012-12-13)
Jin, Bing
;
Su, Man-Nung
;
Lin, Jim Jr-Min
;
應用化學系
;
Department of Applied Chemistry
Ozone-water complex has been thought to play a role in producing atmospheric OH radicals through its photolysis. Here, we re-examined the absorption cross-section of the ozone-water complex with a new method to tell whether the above speculation is valid. With argon solvation and photoionization by tunable vacuum ultraviolet light, we were able to selectively probe the ozone-water 1:1 complex. The measured cross-section of the complex is only similar to the sum of the cross-sections of ozone and water monomers at 157.6, 248.4, and 308.4 nm. In addition, we did not observe any absorption of the complex at 351.8 nm. The results indicate that the OH production through the photolysis of the ozone-water complex is much slower than previously thought.
Note: A transient absorption spectrometer using an ultra bright laser-driven light source
(2013-08-01)
Su, Man-Nung
;
Lin, Jim Jr-Min
;
應用化學系
;
Department of Applied Chemistry
An apparatus to measure transient absorption spectra for short-lived species in the gas phase was built. This was achieved by coupling a laser-driven plasma light source to a time-gated intensified-CCD spectrometer. Although the laser-driven light source features high brightness, ultra broad bandwidth and long lifetime, we found it possesses a plasma oscillation at a frequency of similar to 200 kHz with a peak-to-peak amplitude of similar to 7%. This oscillation caused significant variation of the baseline of the transient absorption spectra even after averaging. To reduce this problem, we synchronized the detector gate time with the phase of the plasma oscillation. This arrangement results in much greater stability of the spectral baseline. We have tested the performance of the whole system with the time-resolved absorption spectra of excited NO3 radicals produced by pulsed laser photolysis of N2O5. (C) 2013 AIP Publishing LLC.
Optical Characterization of Gold Nanoblock Dimers: From Capacitive Coupling to Charge Transfer Plasmons and Rod Modes
(2018-08-09)
Su, Man-Nung
;
Sun, Quan
;
Ueno, Kosei
;
Chang, Wei-Shun
;
Misawa, Hiroaki
The optical properties of plasmonic dimers consisting of two adjacent metal nanoparticles can be tuned over a broad spectral range by changing only slightly the dimer geometry. Most drastic are the changes in the smallest interparticles distances, and often only optical spectroscopy together with electromagnetic simulations yields insights into the geometry of the junction. Here, we study the coupling of gold nanoblock dimers, two square nanoantennas with different nanogaps between their closest corners. We identify three different coupling regimes-capacitively coupled, conductively bridged, and fused dimers-and optically characterize the transitions between them. By combining sample array fabrication, single-particle hyperspectral measurements, and electromagnetic simulations, we were able to examine in detail the effects of junction geometry on the resonance energy and intensity of the plasmon modes supported by gold nanoblock dimers.