With a step-scan Fourier-transform spectrometer we recorded temporally resolved infrared absorption spectra of CH3OO radicals that were produced upon irradiation of CH3COCH3 and O2 at 193 nm in a flowing mixture. At a resolution of 0.15 cm(-1), the rotational structure of the ν2 band of CH3OO near 2954.4 cm(-1) is partially resolved and shows an unexpectedly broadened, and somewhat distorted, Q-branch. A 4D model Hamiltonian, consisting of three CH stretches and the methyl torsion, was developed to explore the origins of this broadening. The vibrational progressions predicted by the model Hamiltonian and the rotational contours of the ν2 band, based on experimental ground-state rotational parameters and their values scaled by their calculated ratios for the upper state, produced simulations in satisfactory agreement with the observed spectrum. These results provide new insight into the vibrational couplings in CH3OO.

Our group has utilized a step-scan FTIR spectrometer operating in the absorption mode to characterize transient species in chemical reactions upon photo-irradiation of gaseous mixtures in a multipass White cell. The operational temporal resolution is typically 1-10 ms with spectral resolution 0.1-4 cm -1 , depending on conditions. The acquisition of both ac-and dc-coupled signals enables an extraction of minute changes in the large background signal to attain a typical detectable absorbance variation greater than 11 0 -4 . By consideration of reaction mechanisms and comparison of vibrational wavenumbers, IR intensities, and rotational contours predicted with theoretical calculations, we have assigned IR absorption bands of many important atmospheric free radicals and unstable species including their conformers, such as ClCO, ClSO, ClCS, ClCOOH, CH 3 SO 2 , CH 3 SOO, CH 3 OSO, CH 3 SO, CH 3 OO, CH 3 C(O)OO, CH 2 OO C 6 H 5 CO, C 6 H 5 SO 2 , and C 6 H 5 C(O)OO. The advantages and limitations of this technique to perform spectral and kinetic investigations of transient species in chemical reactions are discussed. (2010-). His main research interests focus on the spectroscopy, kinetics, and ion pumps of the photosynthetic proteins, using various time-resolved approaches including step-scan FTIR, nanosecond-resolved transient absorption, and electrochemical methods. Chiao Tung University. The main research topics pursued concern spectroscopy, kinetics and dynamics of free radicals or unstable species, using diverse methods including step-scan time-resolved FTIR (emission or absorption), matrix isolation using p-H 2 , cavity ringdown, IR-VUV photoionization, and ultrafast lasers. He has identified more than 70 new free radicals, most of which are important in atmospheric, combustion, or planetary chemistry. He has received numerous honors, and was elected asThe step-scan measurements are performed under the master mode of the spectrometer (Thermo Nicolet, NEXUS 870), in which the timing trigger is initiated by the spectrometer. Figure 3 CHEMICAL SOCIETY Fig. 5. Schematic of the White cell. The first and second IR beam paths and the first and second UV photolysis beam paths of the multiply reflected light are shown. Circular dots indicate images of the IR beam at each reflection.

The development of biodiesels is being driven by the need for reducing emissions from diesel engines without modifying engines and for saving energy. The major obstacle to biodiesel commercialization is the high cost of raw materials. Biodiesel from waste cooking oil is an economical source and an effective strategy for reducing the raw material cost. Although biodiesels made from waste cooking oil have been previously investigated, PAH emissions from heavy-duty diesel engines (HDDEs) with catalyzer fueled with biodiesel from waste cooking oil and its blend with ultra-low sulfur diesel (ULSD) for the US-HDD transient cycle have seldom been addressed. Experimental results indicate that ULSD/WCOB (biodiesel made from waste cooking oil) blends had lower PM, HC, and CO emissions but higher CO 2 and NO x emissions when compared with that of ULSD. Using ULSD/WCOB blends instead of ULSD decreased PAHs by 14.1%-53.3%, PM by 6.80%-15.1%, HC by 6.76%-23.5%, and CO by 0.962%-8.65% but increase CO 2 by 0.318-1.43% and NO x by 0.384-1.15%. Using WCOB is an economical source and an effective strategy for reducing cost, and solves the problem of waste oil disposal.

The manifestations of CH stretch/torsion/rotation coupling in the region of the CH stretch fundamentals are explored in the CHOO radical. Following our earlier study of the fundamental in the totally symmetric CH stretch (the ν fundamental), this work focuses on the other two CH stretch fundamentals, ν and ν, which would be degenerate in the absence of a barrier in the potential along the methyl torsion coordinate. The simplest model, which assumes a decoupling of the CH stretch vibrations from the torsion, fails to reproduce several important features of the spectrum. Specifically, the absence of a strong peak around the origin of the ν fundamental and broadening of the strong peak near the origin in the observed spectrum of the ν fundamental are not captured by this model. The origins of these features are explored through two more sophisticated treatments of the torsion/CH stretch couplings. In the first, a four-dimensional potential based on the three CH stretches and the torsion is developed and shown to reproduce both of these features. On the basis of the results of these calculations, the calculated parameters are adjusted to simulate the recorded spectrum. To further explore the torsion/CH stretch couplings in CHOO, a 9-state model Hamiltonian is developed and discussed. The implications of various types of couplings on the observed energy level patterns are also discussed.