研究领域

Physical Chemistry

The generation, detection and characterization of transition metal containing molecules associated with the modeling catalysis are the focus of our current research. Efficacious synthesis of new catalysts will only be accomplished when there is a clear understanding of the associated microscopic molecular steps and achieving this scientific understanding has been a long-standing scientific objective. Theoretical insight, coupled with fundamental experimentation, can be most influential in modeling supported metal cluster and supported molecular catalyst used to process gaseous reagents and effluents (e.g. automobile emission) because of their very molecular nature. It is realistic that the reactions of a single metal atom, or possibly a metal dimer, with simple gaseous reagents are reasonable first order model systems for emulating metal cluster and molecular supported catalysis. These simple and highly quantifiable systems are the focus of the current and proposed research. The information we seek is both the geometric and electronic structure for metal carbides, carbenes, imides, nitrides, thiols, cyanides, halides, hydroxides, and hydrides from the reaction of CH4, NH3, H2S, and CH 3CN, CH3Cl, CH3OH and H2. All experiments to date have depended upon recording and analyzing ultra-high resolution electronic spectra. We have been implementing the laser ablation/supersonic expansion scheme for sample production, which allows us to control the complexity of the spectra by controlling the rotational temperature to as low as 10 K. The electronic temperature of the sample is much higher facilitating studies of low-lying excited states, which are populated in the reaction. Unlike almost all other groups that use these sources, we skim the supersonic expansion to form a well-collimated molecular beam. The skimming and our use of single frequency lasers results in spectral resolution of < 40 MHz linewidth, which is unprecedented for this class of transient molecules and is required for full exploitation of the information content of electronic spectra. Particular emphasis has been, and will continue to be, placed on the determination of ground and excited state permanent electric dipole moments, m, which are the most fundamental electrostatic property of a molecule and enter into the description of numerous phenomena. A comparison of experimentally derived and theoretically predicted values of m is the most useful gauge of the quality of electronic wave function generated by modern computational methods. The experiments include: High-resolution laser induced fluorescence spectroscopy Pump/probe microwave optical double resonance Transient frequency modulation spectroscopy and Time-of-flight mass spectrometry

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“Tungsten Monocarbide, WC: Pure Rotational spectrum and 13C Hyperfine Interactions” Fang Wang and Timothy C. Steimle , J. Chem. Phys. 136, 044312 (2012). http://dx.doi.org/10.1063/1.3679019 “The Pure Rotational Spectrum of Platinum Monocarbide, PtC” Chengbing Qin, Ruohan Zhang, Fang Wang and Timothy C. Steimle, Chem. Phys. Lett. 535,40 (2012). http://dx.doi.org/10.1016/j.cplett.2012.03.058 “Optical Stark Spectroscopy of the Band of Chloro-Methylene, HCCl”, T.C. Steimle, F. Wang, X. Zhuang and Z. Wang J. Chem. Phys. 136, 114309 (2012) . http://dx.doi.org/10.1063/1.3694245 “The electronic spectrum of Si3 I: the triplet D3H system”Reilly, N. J.; Kokkin, D. L.; Zhuang, X.; Gupta, V.; Nagarajan, R.; Fortenberry, R. C.; Maier, J. P.; Steimle, T. C.; Stanton, J. F.; McCarthy, M. C. J. Chem. Phys. 136(19), 194307/1-194307/(2012). http://dx.doi.org/10.1063/1.4704672 “The Zeeman effect in the [17.6]7.5–X18.5 transition of holmium monoxide” C. Linton, T.C. Steimle and H. Wang, J. Mol. Spectrosc. 275, 15-20 (2012). http://dx.doi.org/10.1016/j.jms.2012.04.009 “The permanent electric dipole moment and hyperfine interactions in platinium monofluoride” C. Qin, R. Zhang, F. Wang and T.C. Steimle, J. Chem. Phys. 137(5), 054309/1-054309/9 (2012). http://dx.doi.org/10.1063/1.4734596 “ Optical Zeeman spectroscopy of the (0,0)B4-X4band systems of titanium monohydride, TiH, and titanium monodeutide, TiD,” ,C. Qin, C. Linton and T.C. Steimle J. Chem. Phys. 137(7), 074301/1-074301/7. (2012). http://dx.doi.org/10.1063/1.4745557 “Optical Stark Spectroscopy of the (3,0) A1+-X1+ Band System of Barium Sulfide, BaS” Chengbing Qin and Timothy C. Steimle, J. Molecular Spectroscopy ,281, 1-3 (2012). http://dx.doi.org/10.1016/j.jms.2012.09.003 “The Molecular Frame Electric Dipole Moment and Hyperfine Interactions in Hafnium Fluoride, HfF” Anh Le, Timothy C. Steimle, Leonid Skripnikov and Anatoly V. Titov, J. Chem. Phys., 138, 124313-1 ̶ 124313-1 (2013). http://dx.doi.org/10.1063/1.4794049 “A Molecular-Beam Optical Stark and Zeeman Study of the [17.8] 0+-X1+ (0.0) band of AuF” Timothy C. Steimle, Ruohan Zhang, Chengbing Qin and Thomas D. Varberg ; Journal of Physical Chemistry A, 117(46), 11737-11744 (2013). http://dx.doi.org/10.1021/jp402045k “Hyperfine Interactions and Electric Dipole Moments in the [16.0]1.5(v=6), [16.0]3.5(v=7) and X2Δ5/2 States of Iridium Monosilicide, IrSi” Anh Le, Timothy C. Steimle, Michael Morse, Maria A. Garcia,Lan Cheng and John F. Stanton, Journal of Physical Chemistry A (2013), 117(50), 13292-13302. http://dx.doi.org/10.1021/jp404950p “The pure rotational spectrum of ruthenium monocarbide, RuC, and relativistic ab intio predictions” Fang Wang, Timothy C. Steimle, Allan G. Adam, Lan Cheng, and John F. Stanton, Journal of Chemical Physics (2013), 139(17), 174318/1-174318/6 http://dx.doi.org/10.1063/1.4828458 “Analysis of hyperfine structure in the 0–0 band of the [17.6]2.5–X2.5 transition of iridium monoxide, IrO” Allan Adam, Colin Linton and T.C. Steimle J. Mol. Spectrosc 295,7-14 (2014) http://dx.doi.org/10.1016/j.jms.2013.10.006 “The Permanent Electric Dipole Moment of Thorium Sulfide, ThS” Anh Le, Michael C. Heaven* and Timothy C. Steimle, J. Chem. Phys. 140, 024307 (2014) http://dx.doi.org/10.1063/1.4861045 “Optical Zeeman Spectroscopy of the (0,0) A2 – X 2+Band System of Magnesium Hydride, MgH” Ruohan Zhang and Timothy C. Steimle ApJ, 781:51 (7pp), 2014 January 20 http://dx.doi.org/10.1088/0004-637X/781/1/51 “Radiative branching ratios for the excited states of 174YbF: application to laser cooling” I.J. Smallman, F. Wang, T.C. Steimle, M.R. Tarbutt, and E.A. Hinds J. Mol. Spectrosc (accepted) http://arxiv.org/abs/1401.4882v2 “The hyperfine interaction in the odd isotope of ytterbium fluoride,171YbF” Zachary Glassman, Richard Mawhorter, Jens-Uwe Grabow, Anh Le and Timothy C. Steimle, J. Mol. Spectrosc 300 (2014): 7-11 http://dx.doi.org/10.1016/j.jms.2014.02.003 “Introduction to the Special issue Spectroscopic Test of Fundamental Physics” Timothy C. Steimle and Wim Ubachs, J. Mol. Spectrosc 300, 1-2 (2014). http://dx.doi.org/10.1016/j.jms.2014.04.004 “The electric dipole moment of cobalt monoxide”, Xiujuan Zhuang and Timothy C. Steimle, J. Chem. Phys. 140, 124301 (2014). http://dx.doi.org/10.1063/1.4868551 “Stark and Zeeman Effect in the [18.6]3.5-X(1)4.5 Transition of Uranium Monofluoride” Colan Linton, Allan Adam and Timothy C. Steimle J. Chem. Phys. (accepted 2014). http://dx.doi.org/10.1063/1.4880255 “The Electric Dipole Moment of Magnesium Deuteride” Timothy C. Steimle, Ruohan Zhang and Hailing Wang, Steimle J. Chem. Phys. 140, 224308 (2014). http://dx.doi.org/10.1063/1.4878414 “The permanent electric dipole moment of nickel oxide , NiO” Damian Kokkin, David Dewberry and Timothy C. Steimle Chemical Physics Letters (accepted June 2014). http://dx.doi.org/10.1016/j.cplett.2014.06.027