Laboratory investigation of visible shuttle glow mechanisms

Laboratory experiments designed to uncover mechanistic information about the spectral and spatial characteristics of shuttle glow were conducted. The luminescence was created when a pulse of O atoms traveling at orbital velocities was directed toward NO molecules previously adsorbed to aluminum, nickel, and Z306 Chemglaz (a common baffle black) coated surfaces held at various temperatures. Spectral and spatial measurements were made using a CCD imaging spectrometer. Corroborative spectral information was recorded in separate measurements using a scanning monochromator and gated photomultiplier arrangement. The e-folding distance at several temperatures was calculated from images of the surface glow using the photometrics image processing capability of the imaging spectrometer. The e-folding distance was not altered as a function of incoming O beam velocity. The results are presented and the observations provide direct evidence that the visible shuttle glow results from recombination of oxygen atoms and surface bound NO

Complex and sustained quantum beating patterns in a classic IVR system: the 3¹5¹ Level in S₁ p-difluorobenzene

Using picosecond time-resolved photoelectron imaging we have studied the intramolecular vibrational energy redistribution (IVR) dynamics that occur following the excitation of the 3151 level which lies 2068 cm-1 above the S1 origin in p difluorobenzene. Our technique, which has superior time resolution to that of earlier studies but retains sufficient energy resolution to identify the behavior of individual vibrational states, enables us to determine six distinct beating periods in photoelectron intensity, only one of which has been observed previously. Analysis shows that the IVR dynamics are restricted among only a handful of vibrational levels, despite the relatively high excitation energy. This is deduced to be a consequence of the high symmetry and rigid structure of p-difluorobenzene

Engineering Corynebacterium glutamicum for isobutanol production

The production of isobutanol in microorganisms has recently been achieved by harnessing the highly active 2-keto acid pathways. Since these 2-keto acids are precursors of amino acids, we aimed to construct an isobutanol production platform in Corynebacterium glutamicum, a well-known amino-acid-producing microorganism. Analysis of this host’s sensitivity to isobutanol toxicity revealed that C. glutamicum shows an increased tolerance to isobutanol relative to Escherichia coli. Overexpression of alsS of Bacillus subtilis, ilvC and ilvD of C. glutamicum, kivd of Lactococcus lactis, and a native alcohol dehydrogenase, adhA, led to the production of 2.6 g/L isobutanol and 0.4 g/L 3-methyl-1-butanol in 48 h. In addition, other higher chain alcohols such as 1-propanol, 2-methyl-1-butanol, 1-butanol, and 2-phenylethanol were also detected as byproducts. Using longer-term batch cultures, isobutanol titers reached 4.0 g/L after 96 h with wild-type C. glutamicum as a host. Upon the inactivation of several genes to direct more carbon through the isobutanol pathway, we increased production by ∼25% to 4.9 g/L isobutanol in a ∆pyc∆ldh background. These results show promise in engineering C. glutamicum for higher chain alcohol production using the 2-keto acid pathways

THE PHOSPHORESCENCE EXCITATION SPECTRUM OF JET COOLED BENZALDEHYDE1BENZALDEHYDE{^{1}}

Address of Holtzclaw and Pratt: Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260. 1 Work supported by NSF (CHE-8402996).Author Institution:Recent experiments have demonstrated the feasibility of laser-induced phosphorescence experiments $\underline{via}$ direct pumping of the triplet state in a supersonic jet. We have extended the method in a probe of the $^{3}A^{\prime\prime} (n\pi^{\ast})$ system of the simplest aromatic carbonyl, benzaldehyde. Spectra at both low $(0.6 cm^{-1})$ and moderate $(0.06 cm^{-1})$ resolution have been obtained. Rotational and vibrational analyses of these data are in progress, the results of which will be given. Comparisons with theoretical and solid state work will be made allowing comment on vibronic coupling between the $^{3}n\pi^{\ast}$ state and a near degenerate $^{3}n\pi^{\ast}$ state as well as other issues

ROTATIONAL ENERGY TRANSFER IN THE B3Π(0+)B^{3}\Pi(0_{+}) STATES OF IF AND ICI: A SYSTEMATIC STUDY OF STATE-TO-STATE RATE COEFFICIENTS∗COEFFICIENTS^{\ast}

$^{\ast}$Supported by Air Force Office of Scientific Research Contract No. F49620-86-C-0061.Author Institution: Physical Sciences Inc.A CV laser induced fluorescence study has been performed to determine rotational to translational (R-T) energy transfer rate coefficients for selected J' levels in the heteronuclear molecules IF and ICl. Steady state populations of specific rovibronic levels were prepared using either an $Ar^{+}$ laser or a ring dye laser. Rate coefficients were determined for state-to-state R-T transfer for a variety of bath gases: $He, Ne, Ar, Kr, Xe, N_{2}$, and $CF_{4}$ and for several initially excited rotational levels. Over 1000 rate coefficients for individual $\Delta J$ changing collisions have been measured. Dramatic differences in the abilities of various collision partners to transfer angular momentum to and from IF and ICI are observed. Comparisons are made to theoretical models that predict the scaling of the rate coefficients as a function of $\Delta J$

ROTATIONAL STRUCTURE IN THE SINGLET-TRIPLET EXCITATION SPECTRA OF POLYATOMIC MOLECULES.1MOLECULES.^{1}

$^{1}$ Work supported by NSF. $^{2}$ J. T. Hougen. Can. J. Phys. 42. 433 (1964).Author Institution: Department of Chemistry, Montana State University.; Physical Sciences. Inc., Research Park. Andover. MA 01810.; Department of Chemistry., University of Pittsburgh,We have observed rotational structure in the beam- and jet-cooled $T_{1}\leftarrow S_{0}$ phosphorescence excitation spectra of several molecules, including glyoxal, pyrazine and benzaldehyde. Each observed resolved or partially-resolved contour exhibits a significantly different shape, a shape that is also different from the corresponding bands in the $S_{1}\leftarrow S_{0}$ spectrum. We will discuss the origin of these differences in this talk. Our approach is that of $Hougen_{2}$ which emphasizes the strong connection between the radiative properties of the triplet state in the gas and condensed phase, in a natural way