18 research outputs found
2012: CLE: Beyond the Advertisement: Marketing and Business Development for Lawyers
No full textThe purpose of this course is to provide some basic, practical knowledge and skills for developing and implementing business marketing plans for both firms and individual attorneys. The skills acquired are transferable to a variety of practice venues, su
FINDING THE ELUSIVE IODOCARBENE: FLUORESCENCE EXCITATION AND SINGLE VIBRONIC LEVEL EMISSION SPECTROSCOPY OF CHI
No full textM.~K.~Gilles, K.~M.~Ervin, J.~Ho, and W.~C.~Lineberger, J.~Phys.~Chem. 96, 1130 (1992).Author Institution: Department of Chemistry, Marquette University, Milwaukee, WI 53233; Department of Chemistry, Brookhaven National Laboratory, Upton, NY 11973Among the triatomic halocarbenes, only the iodocarbenes remain to be characterized. The search for these elusive species is motivated by a controversy regarding the multiplicity of the ground state. Photoelectron spectra of Lineberger and co-workers suggest a triplet ground state for CHI, at variance with recent studies, which suggest a singlet ground state with a singlet-triplet gap of around 4 kcal mol. In this work, we have succeeded in finding the spectra of CHI and its deuterated isotopomer using pulsed discharge jet spectroscopy. Rotationally resolved fluorescence excitation spectra are consistent with a singlet-singlet transition, and the derived rotational constants are in good agreement with theoretical predictions. Single vibronic level emission spectra confirm a singlet multiplicity for the ground state, and reveal extensive mixing of the singlet and triplet levels at higher energy. We are able to set a lower limit on the singlet-triplet gap of 4.1 kcal mol, in excellent agreement with theory. Extrapolation of the observed bending levels for CHI and CDI to a common origin suggests that the origin of the ^{1}A^{\prime\prime}^{-1}$, and we will report on high resolution measurements near the electronic origin made at Brookhaven National Laboratory
THEORETICAL STUDY OF THE SPECTROSCOPY AND DYNAMICS OF THE VINYLIDENE-ACETYLENE ISOMERIZATION
No full textR. Schork, and H. K\""{o}ppel, Theor. Chem. Acc. 100, 204 (1998). K. M. Ervin, J. Ho, and W. C. Lineberger, J. Chem. Phys. 91, 5974 (1989).Author Institution: Theoretical Chemistry, University of HeidelbergThe results of 5D ab initio quantum dynamical study of the vinylidene - acetylene isomerization reaction are presented. The study is based on a new ab initio potential energy surface for the planar system, obtained with the CCSD(T) method and the cc-pVTZ basis set. The dynamics is studied with grid methods, using 4-atom Jacobi-like coordinates and wave packet propagation techniques. The results of a 3D treatment, including the 2 angular degrees of freedom and the C-C stretching mode, have been reported earlier in the . Including all (planar) degrees of freedom, the experimental photodetachment spectrum of Lineberger and is very well reproduced. Furthermore, lifetimes for broadband excitation and for individual vibrational levels of vinylidene have been computed, the latter with the aid of filter diagonalization techniques. The lifetimes are 2-3 orders of magnitude longer that previously believed, indicating a surprising stability of this reactive intermediate. Similar results have been obtained for the deuterated species, supporting the above conclusions
SOLVENT-MEDIATED ELECTRON LEAPFROGGING: CHARGE TRANSFER IN IBr(CO) PHOTODISSOCIATION
No full textAuthor Institution: Department of Chemistry, The Ohio State University, Columbus, OH 43210; JILA, Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder, CO 80309In this work, we investigate the time-resolved photoelectron spectra of IBr(CO).}, {\bf{2010}}, {\it{in press}}.} In the photodetachment studies performed by Lineberger and co-workers, IBr(CO) is prepared in its electronic ground state () whereupon it is excited to its {\it{\~{A}}} () excited state, before electron photodetachment/photoionization and dissociation on the {\it{\~{C}}} () excited state of IBr. Previous experimental work showed that dissociation of bare IBr yields only I + Br products.}, {\bf{2005}}, {\it{122}}, 174305.} However in IBr(CO), a small fraction ( 3\%) of the dissociating molecules undergo an electron transfer from I to Br at 350 fs after the initial excitation. Thus a single solvent molecule can initiate a non-adiabatic transition from the {\it{\~{A}}} state to either the lower {\it{\~{A}}} or {\it{\~{X}}} state, thereby producing I + Br (+ CO) prior to photoionization. To study the dynamics, we perform high level {\it{ab initio}} calculations (MR-SO-CISD/aug-cc-pVTZ(-PP)) as well as classical molecular dynamics (MD) simulations. The MD simulations capture much of the dynamics of the photodissociation but underestimate the charge-transfer channel. Results of the {\it{ab initio}} calculations show how CO bend vibrational excitation could increase the percentage of non-adiabatic transitions and how the CO modifies the charge distribution of IBr to make the charge transfer accessible. The proposed mechanism and timescales are consistent with the observed Br products
APPLICATIONS OF NEGATIVE ION SPECTROSCOPY TO DETERMINATIONS OF ELECTRON AFFINITIES AND BOND DISSOCIATION ENERGIES
No full textAuthor Institution: Department of Chemistry and Biochemistry, University of Colorado, and Joint Institute for Laboratory AstrophysicsNegative ion spectroscopy provides a direct method for determination of electron affinities of atoms and small molecules. The photodetachment process also provides direct information on electronic excitation energies of the corresponding neutral species. We present a summary of the vinylidene acetylene isomerization as studied by this technique. Electron affinities may also be used in a thermochemical cycle involving the gas phase acidity of the corresponding acid to obtain homolytic bond dissociation energies. We will use this cycle to explore bond dissociation energies as acetylene and ethylene are completely dissected to their atomic constituents
MEASUREMENT OF THE VIBRATION-ROTATION SPECTRUM OF THE HYDROXIDE ANION () BY VELOCITY MODULATION LASER SPECTROSCOPY
No full text. T. J. Lee and H. F. Schaefer III, J. Chem. Phys. 83, 1784 (1985). 2. H.-J. Werner, P. Rosmus, and E.-A. Reinsch, J. Chem. Phys. 79, 905 (1983). 3. P.A. Schulz, R.D. Mead, P. L. Jones, and W.C. Lineberger, J. Chem. Phys. 77, 1153 (1982). 4. N.H. Rosenbaum, J. C. Owrutsky, L. M. Tack, and R.J. Saykally, J. Chem. Phys. (accepted). Address of Rosenbaum, Owrutsky, Tack, and Saykally: Department of Chemistry, University of California, Berkeley, CA 94720.Author Institution:Guided by the ab initio predictions for the fundamental made by Lee and Schaefer (1) and by Werner, Rosmus, and Reinsch (2) along with the laser photodetachment results of Schulz et al. (3), we measured the band of and by velocity modulation spectroscopy with a color center laser (4). The concentration was found to be maximized in a or discharge where the addition of argon both rotationally heats the and increases its overall concentration. The signal was also found to be dramatically dependent on the presence of metal sputtered on the discharge cell wall. The and bands were analyzed separately with a least squares analysis yielding the equilibrium bond length and vibration-rotation constants through sextic distortion terms. Using the band origins of the two isotopomers, the harmonic vibrational frequencies and first order anharmonicities were calculated
ROTATIONALLY RESOLVED NEAR-INFRARED SPECTRUM OF HCBr
No full textS, Xu, K, A, Beran, and M. D. Harmony, J. Phys. Chem. 98, 2742(1994). M.K. Gilles, K. M. Ervin, J. Ho, and W. C Lineberger, J. Phys. Chem, 96, 1130 (1992)Author Institution: Department of Chemistry, Brookhaven National laboratoryThe Rotationally resolved spectrum of bromomethylece (HCBr) in the vicinity of was obtained at Doppler limited resolution using a transient frequency-modulation absorption technique. In contrast to the better studied halomethylence (HCF and HCCI), the number of experimentalo investigations on HCBr is very limited. Xu reported the spectrum at visible wavelengths, but no rotational structure was resolved. Gilles have used photoelectron specroscopy to determined the singlet-triplet seperation to be 2.62.2 k.cal/mol. Based upon previous , we tentatively assign the observed band to be the transition. The analysis of the observed spectrum will be discussed. Acknowledgment: This work was carried out under Contrct no. De-AC02-76CH00016 with the U.S. Department of Energy and supported by its Division of Chemical sciences, Office of basic Energy Sciences
OBSERVATION OF THE ELECTRONIC TRANSITION OF BUTYL PEROXY RADICALS USING CAVITY RINGDOWN SPECTROSCOPY.
No full textT. J. Wallington, P. Dagaut, and M. J. Kurylo, Chem. Rev. 92, 667(1992) E. P. Clifford, P. G. Wenthold, R. Gareyev, W. C. Lineberger, C. H. DePuy, V. M. Bierbaum, and G. B. Ellison, J. Chem. Phys. 109, 10293 (1998)Author Institution: Laser Spectroscopy Facility, Department of Chemistry, The Ohio State UniversityAn important reaction involving the low temperature oxidation of hydrocarbons concerns the production of alkyl peroxy radicals . These species of highly reactive molecules are present in atmospheric reactions, as well as internal combustion engines. Longer carbon chain alkyl peroxy radicals, i.e. butyl peroxy radical, are especially important in combustion processes because of their ability to rapidly isomerize thereby opening new branching and propagation channels in the chain reaction. Therefore, it is useful to develop a database of information concerning alkyl peroxy radicals with multiple carbon atoms. In the case of butyl peroxy radical, most have focused only on t-butyl peroxy radical, neglecting the other isomers. Cavity ringdown spectroscopy (CRDS) has been applied to study the near-IR electronic transition of the isomers of the butyl peroxy radical. The four isomers of the butyl peroxy radical are n-butyl, sec-butyl, isobutyl, and t-butyl peroxy radical. We report on the cavity ringdown spectra of the electronic transition of n-butyl, sec-butyl, isobutyl, and t-butyl peroxy radicals. The bands that have been observed are the origin and oxygen-oxygen stretch for each isomer. Also, transitions from several different conformers have been detected
PHOTOELECTRON SPECTROSCOPY AND DYNAMICS OF ICN
No full textAuthor Institution: JILA, Department of Chemistry and Biochemistry, University of Colorado at Boulder, Boulder; CO 80309We report the photoelectron spectrum of ICN and preliminary UV photodissociation studies of ICN. Because CN behaves like a pseudo-halogen, we compare our results to previous spectroscopic and dynamical work on dihalides, such as I, IBr, and ICl. The photoelectron spectrum of ICN resembles that of IBr with transitions to the ground electronic state and two excited states. The transition to the ground electronic state of ICN is broad (FWHM 0.75 eV) and structureless which corresponds to accessing high lying vibrational states. Transitions to the excited states are narrow and spaced by 0.13 eV. A complete analysis of the photoelectron spectrum is underway to determine the structure and energetics of ICN and neutral ICN. In addition, preliminary nanosecond studies of ICN UV photodissociation are reported. In these two-photon experiments, one photon dissociates ICN and the second photon detects anionic products via photoelectron spectroscopy. Following excitation ( = 260 nm) to a dissociative electronic state of ICN, we observe two anionic photoproducts: I and CN. The presence of both photoproducts could be a result of a non-adiabatic transition midway through photodissociation or excitation to two different anionic states which asymptotically correlate to distinct products. Currently, time-resolved photoelectron studies are underway to determine the actual dissociation pathway. This research is being funded by NSF and AFOSR
