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CreatorTitleDescriptionSubjectDate
26 Armentrout, Peter B.Threshold behavior of endothermic reactions: C+(2P) + H2 → CH+ + HThe reaction C+(2p) + H2 → CH+ + H (1) and its deuterium analog is a model system in ion-molecule chemistry. It is of interest due to its astrophysical significance, because it is an endothermic process, and because the interaction involves several potential energy surfaces. Experimental work ha...Endothermic reactions; Translational energy; Threshold behavior1984
27 Olson, Randall J.; Coldwell, Karin D.; Compton, Bruce J.; Giddings, John C.Sedimentation field-flow fractionation: a method for studying particulates in cataractous lensIt is shown that the technique of sedimentation field-flow fractionation (sedimentation [sed] FFF) can be used to determine the particle content and particle size distribution of normal and cataractous lenses. A 31-year-old normal human lens, for example, showed a particle content of 1.5% by weight ...Fractionation; Cataractous Lens; Particulates1984
28 Miller, Joel Steven; Epstein, Arthur J.Noise-power studies of the nearly commensurate quasi-one-dimensional conductor (N-methylphenazinium)x(phenazine)1-x(7,7,8,8-tetracyano-p-quinodimethane) [(NMP)x(Phen)1-x(TCNQ)We report the noise power of (NMP)x(Phen)1-x(TCNQ) as a function of temperature (100 <_ T <_ 300 K), frequency (1<_f<_10(4) Hz), electric field (0 <_E<_300 V/cm), and conduction-electron density (0.49<_x<_0.59). The results for the commensurate, doped commensurate, and incommensurate regimes are sim...Fluctuations; Solitons1985
29 Armentrout, Peter B.Translational energy dependence of Ar+ + XY → ArX+ + Y (XY = H2, D2, HD) from thermal to 30 eV c.m.Cross sections for the reactions of Ar+ with H2, D2, and HD to form ArH + and ArD + are measured using a new guided ion beam tandem mass spectrometer which affords an experimental energy range from 0.05 to 500 eV laboratory. The apparatus and experimental techniques are described in detail. Cross se...Translational energy; Ion-molecule reactions; Ion energy; Argon; Hydrogen; Endothermic reactions1985
30 Poulter, Charles Dale; Davis, Darrell R.15N labeled e. coli tRNAMet, tRNAGlu, tRNATyr, and tRNAPhe. Double resonance and two dimensional NMR of H-N1 units in pseudouridineThe N1 imino units in Escherichia coli tRNAfMet, tRNAGlu, tRNAPhe, and tRNATyr were studied by 1H-15N NMR using three different techniques to suppress signals of protons not attached to 15N. Two of the procedures, Fourier internuclear difference spectroscopy and two-dimensional forbidden echo spectr...Escherichia coli; Magnetic resonance spectroscopy; Nucleic acid conformation1985-08-15
31 Poulter, Charles Dale; Davis, Darrell R.15N-labeled Escherichia coli tRNAfMet, tRNAGlu, tRNATyr, and tRNAPhe. Double resonance and two-dimensional NMR of N1-labeled pseudouridine.The N1 imino units in Escherichia coli tRNAfMet, tRNAGlu, tRNAPhe, and tRNATyr were studied by 1H-15N NMR using three different techniques to suppress signals of protons not attached to 15N. Two of the procedures, Fourier internuclear difference spectroscopy and two-dimensional forbidden echo spectr...Escherichia coli; Magnetic resonance spectroscopy; Nitrogen; Nucleic acid conformation1985-08-15
32 Armentrout, Peter B.C+(2P)+H2(D2,HD)→CH+(CD+)+H(D). I. Reaction cross sections and kinetic isotope effects from threshold to 15eV c.m.Total cross sections for the reactions of carbon (1 + ) ions with isotopic molecular hydrogen (H2, D2, and HD) to form methyliumylidene (CH+ and CD+) have been measured using guided ion beam techniques. Cross sections are reported as a function of the translational energy of the reactants from th...Methyliumylidene; Endothermic reactions; Isotope effect; Threshold energy1986
33 Armentrout, Peter B.Effect of kinetic and electronic energy on the reactions of Mn+ with H2, HD and D2Reactions of several electronic states of Mn+ with H2, HD, and D2 have been examined using guided ion beam mass spectroscopy. The excitation function for the ground state of Mn+ ( 75) has two regions: one of very low reactivity at threshold and another more efficient pathway at higher energies. In ...Ion-molecule reactions; Translational energy; Bond energy; Threshold behavior; Endothermic reactions; Metal ions; Manganese; Hydrogen1986
34 Armentrout, Peter B.C+(2P) + H2(D2,HD)→CH+(CD+) + H(D). I. Reaction cross sections and kinetic isotope effects from threshold to 15 eV c.m.Total cross sections for the reactions of carbon (1 + ) ions with isotopic molecular hydrogen (H2, D2 , and HD) to form methyliumylidene (CH+ and C D + ) have been measured using guided ion beam techniques. Cross sections are reported as a function of the translational energy of the reactants fro...Ion-molecule reactions; Isotope effects; Translational energy; Threshold behavior; Endothermic reactions1986
35 Armentrout, Peter B.Kinetic energy dependence of Al+ + O2→AlO+ + OThe endothermic reaction of Al+ with O2 is studied using a guided ion-beam apparatus. The reaction cross section is measured as a function of kinetic energy from 0 to 20 eV. The threshold energy for the reaction, E0, is determined from an empirical model to be 3.64 ± 0.04 eV.Ion-molecule reactions; Translational energy; Threshold behavior; Endothermic reactions; Aluminum; Oxygen1986
36 Miller, Joel Steven; Epstein, Arthur J.Ferromagnetic properties of one-dimensional decamethylferrocenium tetracyanoethylenide (1:1): [Fe(n5-C5Me5)2].+[TCNE].-[Fe(C5Me5)2].+ [TCNE].-- has been characterized by magnetic susceptibility to possess dominant ferromagnetic interactions; its structure has been determined by X-ray crystallography.Susceptibility; Crystal; Magnetic1986
37 Armentrout, Peter B.Spin-orbit state-selected reactions of Kr+(2P3/2 and 2P1/2) with H2, D2, and HD from thermal energies to 20 eV c.m.Spin-orbit state-selected reactions of K r + (2Pj), J = 3/2 and / = 1/2, with isotopic molecular hydrogen (H2 , D2 , and HD) to form KrH+ and Kr D+ are investigated using guided ion beam techniques. Reaction cross sections for each spin-orbit state are measured as a function of the relative trans...Spin-orbit; Krypton ions; Hydrogen isotopes; Isotope effects; Potential energy surfaces; Ion-molecule reactions1986
38 Armentrout, Peter B.Transition metal cluster ion chemistryThe reactivity and thermochemistry of ionic metal atoms and clusters has been explored using guided ion beam mass spectrometry. With this apparatus, cross sections of ion-molecule reactions can be measured from thermal energies to hundreds of eV. Application to metal cluster chemistry demonstrates...Metal clusters; Manganese ions; Endothermic reactions1986
39 Miller, Joel Steven; Epstein, Arthur J.Linear chain ferromagnetic charge transfer compoundsCharge transfer complexes possessing a ... DADA ... structure with both the donor, D, and acceptor, A, being S = 1/2 radicals may exhibit cooperative magnetic phenomena. The complex [Fe(C5Me5)2]+ [TCNQ]-. exhibits metamagnetic behavior. The similarly structured [TCNE]-. and [C4(CN)6]-. complexes ar...Spin; Exchange; Molecular1986
40 Poulter, Charles Dale; Davis, Darrell R.15N-labeled tRNA. Identification of dihydrouridine in Escherichia coli tRNAfMet, tRNALys, and tRNAPhe by 1H-15N two-dimensional NMR.The N3 imino units of dihydrouridine were identified in samples of 15N-labeled Escherichia coli tRNAfMet, tRNALys, and tRNAPhe by 1H-15N two-dimensional NMR. The peaks for dihydrouridine had high field 1H (9.7-9.8 ppm) and 15N (147.8-149.5 ppm) chemical shifts. Assignments were made by 1H-15N chemic...Hydrogen Bonding; Magnetic Resonance Spectroscopy; Magnetic Resonance Spectroscopy1986-03-15
41 Poulter, Charles Dale; Davis, Darrell R.15N-labeled tRNA. Identification of 4-thiouridine in Escherichia coli tRNASer1 and tRNATyr2 by 1H-15N two-dimensional NMR spectroscopy.Uridine is uniquely conserved at position 8 in elongator tRNAs and binds to A14 to form a reversed Hoogsteen base pair which folds the dihydrouridine loop back into the core of the L-shaped molecule. On the basis of 1H NMR studies, Hurd and co-workers (Hurd, R. E., Robillard, G. T., and Reid, B. R. ...Magnetic resonance spectroscopy1986-09-15
42 Miller, Joel Steven; Epstein, Arthur J.Optical properties of the 1:2 compound of dimethylferrocenium with tetracyanoquinodimethanide: [(Me2Fc)(TCNQ)2]We present the results of a study of the room-temperature polarized reflectance of (1:2) 1,1'-dimethylferrocenium ditetracyanoquinodimethanide [(Me2Fc)(TCNQ)2] over the range between the far infrared and the near ultraviolet. Kramers-Kronig analysis of the reflectance is used to determine the optica...Reflectance; Electrons ; Molecules1987
43 Armentrout, Peter B.Effect of kinetic and electronic energy on the reactions of Cr+ with H2, HD, and D2The reactions of atomic chromium ions with H2 , HD, and D2 are examined using guided ion beam tandem mass spectrometry. The ground electronic state (6S) is found to react inefficiently. The thresholds of these data are analyzed to yield a 0 K bond dissociation energy for CrH+ of 1.37 ± 0.09 eV (31...Chromium ions; Hydrogen; Deuteride; Bond energy1987
44 Poulter, Charles DaleTrisammonium geranyl diphosphateGeranyl chloride. To a flame-dried, 100-mL, three-necked, round-bottomed flask equipped with a magnetic stirrer, low temperature thermometer, rubber septum, and nitrogen inlet adapter, is added 1 .47 g (11 mmol) of N-chlorosuccinimide (Note 1) . The powder is dissolved in 45 mL of dry dichloromet...Buffer; Solution; Chloride1987
45 Miller, Joel Steven; Epstein, Arthur J.Ferromagnetism in molecular decamethylferrocenium tetracyanoethylenide: (DMeFc TCNE)The temperature and magnetic field dependence of the magnetization and susceptibility of single-crystal decamethylferrocenium tetracyanoethenide demonstrate that this material is the first molecular compound with a ferromagnetic ground state. A spontaneous magnetization is observed for T < 4.8 K. T...Magnetization; Ferromagnetic1987
46 Armentrout, Peter B.Energy dependence, kinetic isotope effects, and thermochemistry of the nearly thermoneutral reactions of N+(3P) + H2(HD, D2) → NH+(ND+) + H(D)The reactions of N + (3P) ions with H2 , HD, D2 are examined using guided ion beam tandem mass spectroscopy. Absolute reaction cross sections are measured from near thermal energies to 30 eV relative energy. The low energy cross section behavior is analyzed using empirical threshold models and ph...Thermoneutral reactions; Ion-molecule reactions; Translational energy; Bond energy; Threshold behavior; Phase space theory1987
47 Morse, Michael DavidSpectroscopic studies of the jet-cooled aluminum trimerGas phase spectroscopic investigations of the jet-cooled aluminum trimer are reported using the technique of resonant two-photon ionization with mass spectrometric detection. A discrete band system in the 5200-6100 ? region is observed, consisting of an extended vibrational progression in a single ...1987
48 Miller, Joel Steven; Epstein, Arthur J.Microwave response of confined soliton pairs (Bipolarons) in (N-Methylphenazinium) x (Phenazine) 1-x (Tetracyanoquinodimethanide)The temperature-dependent dielectric response and conductivity at =1010 Hz is reported for the title compound, (NMP)x(Phen)i-x(TCNQ), in the regime 0.50<-x<-0.59, spanning commensurate, bipolaron, and incommensurate regimes. The large and strongly temperature-dependent dielectric constant and o-(101...Dielectric, Proposed, Electrons1987
49 Armentrout, Peter B.Hydrogen atom transfer reactions of He+ and Ne+ with H2, D2, and HDThe hydrogen atom transfer reactions of helium (1 +) and neon(1+) ions with isotopic molecular hydrogen (H2 , D2 , and HD) are investigated using guided ion beam techniques. These reactions are exothermic, but are known to be extremely slow at thermal energies. The cross sections for formation of...Transfer reactions; Ion-molecule reactions; Exothermic reactions; Hydrogen; Helium ions; Neon ions; Threshold behavior; Isotope effects1987
50 Armentrout, Peter B.Translational energy dependence of O+(4S) + N2 → NO+ + N from thermal energies to 30 eV c.m.Guided ion beam mass spectrometry is used to examine the kinetic energy dependence of the reaction of ground state atomic oxygen ion with molecular nitrogen. An 0 + (4S) source which produces less than 0.06% excited states is described. Cross sections for the NO+ + N product channel decrease with...Ion-molecule reactions; Translational energy; Threshold behavior; Endothermic reactions; Nitrogen; Oxygen1987
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