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A single-shot coherent Raman imaging technique has been developed for spatially correlated one-dimensional high-fidelity gas-phase thermometry and multiplex chemical detection in flames. The technique utilizes two-beam phase matching, operating a single ultrashort pump/Stokes excitation pulse (7 fs) and a narrowband picosecond probe pulse (70 ps), interrogating a Raman active window of ∼4200 cm(-1) with ∼0.3 cm(-1) spectral resolution. The measurement geometry is formed intersecting the two beams shaped as laser-sheets and the one-coordinate spatial information is retrieved with a linespread function of

Spatial mapping of temperature and molecular species concentrations is vitally important in studies of gaseous chemically reacting flows. Temperature marks the evolution of heat release and energy transfer, while species concentration gradients provide critical information on mixing and chemical reaction. Coherent anti-Stokes Raman spectroscopy (CARS) was pioneered in measurements of such processes almost 40 years ago and is authoritative in terms of the accuracy and precision it may provide. While a reacting flow is fully characterized in three-dimensional space, a limitation of CARS has been its applicability as a point-wise measurement technique, motivating advancement toward CARS imaging, and attempts have been made considering one-dimensional probing. Here, we report development of two-dimensional CARS, with the first diagnostics of a planar field in a combusting flow within a single laser pulse, resulting in measured isotherms ranging from 450 K up to typical hydrocarbon flame temperatures of about 2000 K with chemical mapping of O2 and N2.

Sum-frequency generation vibrational spectroscopy (SFG-VS) and kinetic measurements using gas chromatography have been used to study the surface reaction intermediates during the hydrogenation of three alpha,beta-unsaturated aldehydes, acrolein, crotonaldehyde, and prenal, over Pt(111) at Torr pressures (1 Torr of aldehyde, 100 Torr of hydrogen) in the temperature range of 295-415 K. SFG-VS data showed that acrolein has mixed adsorption species of eta(2)-di-sigma(CC)-trans, eta(2)-di-sigma(CC)-cis as well as highly coordinated eta(3) or eta(4) species. Crotonaldehyde adsorbed to Pt(111) as eta(2) surface intermediates. SFG-VS during prenal hydrogenation also suggested the presence of the eta(2) adsorption species and became more highly coordinated as the temperature was raised to 415 K, in agreement with its enhanced C=O hydrogenation. The effect of catalyst surface structure was clarified by carrying out the hydrogenation of crotonaldehyde over both Pt(111) and Pt(100) single crystals while acquiring the SFG-VS spectra in situ. Both the kinetics and SFG-VS showed little structure sensitivity. Pt(100) generated more decarbonylation "cracking" product while Pt(111) had a higher selectivity for the formation of the desired unsaturated alcohol, crotyl alcohol.

Pyrrole Hydrogenation over Rh(111) and Pt(111) Single-Crystal Surfaces and Hydrogenation Promotion Mediated by 1-Methylpyrrole: A Kinetic and Sum- Frequency Generation Vibrational Spectroscopy Study Christopher J. Kliewer, Marco Bieri and Gabor A. Somorjai* Department of Chemistry, University of California, Berkeley, California 94720, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 E-mail: somorjai@socrates.berkeley.edu TITLE RUNNING HEAD: Pyrrole hydrogenation over Rh(111) and Pt(111) RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required according to the journal that you are submitting your paper to) CORRESPONDING AUTHOR FOOTNOTE: Gabor A. Somorjai, Tel: 510-642-4053. Fax: 510-643- 9668. E-mail: somorjai@socrates.berkeley.edu. ABSTRACT. Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to study the adsorption and hydrogenation of pyrrole over both Pt(111) and Rh(111) single-crystal surfaces at Torr pressures (3 Torr pyrrole, 30 Torr H 2 ) to form pyrrolidine and the minor product butylamine. Over Pt(111) at 298K it was found that pyrrole adsorbs in an upright geometry cleaving the N-H bond to bind through the nitrogen evidenced by SFG data.

Evanescent-wave cavity ring-down spectroscopy was used to monitor the adsorption of human hemoglobin to a fused-silica surface from aqueous solution. An uncoated dove prism was situated in a ring-down cavity such that the beam entered and exited with a normal-incidence geometry. This afforded ring-down times as high as 5 mus and values of sigma(tau)/tau as low as 0.3%. Normal-incidence geometry permits the detection of both S- and P-polarized light, yielding some information of the orientation of adsorbates. The orientation of the adsorbed hemoglobin molecules is found to change as adsorption progresses, but with a different time profile than adsorption itself. The adsorption kinetics from a quiescent solution is consistent with a reaction-diffusion model that includes both reversible and irreversible adsorption operating in parallel. Systems behaving according to this model also seem to display adsorption isotherms, although the increased adsorption from more concentrated solutions is only a consequence of the system being under kinetic control. In some cases, this may be sufficient to explain the paradox of protein adsorption systems which seem to be both irreversible and consistent with isotherm models as well.

Sum frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have identified at least two reaction pathways for benzene hydrogenation on the Pt(100) and Pt(111) single-crystal surfaces at Torr pressures. Kinetic studies at low temperatures (310-370 K) show that benzene hydrogenation does not proceed through cyclohexene. A Langmuir-Hinshelwood-type rate law for the low-temperature reaction pathway is identified. The rate-determining step for this pathway is the addition of the first hydrogen atom to adsorbed benzene for both single-crystal surfaces, which is verified by the spectroscopic observation of adsorbed benzene at low temperatures on both the Pt(100) and Pt(111) crystal faces. Low-temperature SFG studies reveal chemisorbed and physisorbed benzene on both surfaces. At higher temperatures (370-440 K), hydrogenation of benzene to pi-allyl c-C(6)H(9) is observed only on the Pt(100) surface. Previous single-crystal studies have identified pi-allyl c-C(6)H(9) as the rate-determining step for cyclohexene hydrogenation to cyclohexane.