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Articles 721 - 750 of 795

Full-Text Articles in Biological and Chemical Physics

Correlation Function Formulation For The State Selected Total Reaction Probability, Sophya V. Garashchuk, D. J. Tannor Jan 1998

Correlation Function Formulation For The State Selected Total Reaction Probability, Sophya V. Garashchuk, D. J. Tannor

Faculty Publications

A correlation function formulation for the state-selected total reaction probability, Nα(E), is suggested. A wave packet, correlating with a specific set of internal reactant quantum numbers, α, is propagated forward in time until bifurcation is complete at which time the nonreactive portion of the amplitude is discarded. The autocorrelation function of the remaining amplitude is then computed and Fourier transformed to obtain a reactivity spectrum. Dividing by the corresponding spectrum of the original, unfiltered, wave packet normalizes the reactivity spectrum, yielding the total reaction probability from the internal state, α. The procedure requires negligible storage and just one time-energy Fourier …

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Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Cheettu Ammal Jan 1998

Ab Initio Study Of Formazan And 3-Nitroformazan, G. Buemi, F. Zuccarello, P. Venuvanalingam, M. Ramalingam, Salai Cheettu Ammal

Faculty Publications

Formazan and 3-nitroformazan have been investigated at abinitio level (MP2/6-31G** and B3LYP/6-31G**) in all their possible conformations, for studying the various possibilities of intramolecular hydrogen bonding formation. The trans-syn-s-cis (TSSC), known also asyellowform, has been found to be the most stable conformer (at least in the gas phase) in both compounds. This particular structure is strongly stabilized by a N–H···N hydrogen bridge, which gives rise to a hexatomic chelate ring, with the possibility of a proton transfer process.This closely resembles that of malondialdehyde, previously studied, in the evolution of the …

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Π-Systems As Lithium/Hydrogen Bond Acceptors: Some Theoretical Observations, Salai Cheettu Ammal, P. Venuvanalingam Jan 1998

Π-Systems As Lithium/Hydrogen Bond Acceptors: Some Theoretical Observations, Salai Cheettu Ammal, P. Venuvanalingam

Faculty Publications

Ab initio calculations at the Hartree–Fock and correlated levels and density functional theory calculations have been performed with 6-31++G(d,p) and 6-311++G(d,p)basis sets on LiF and HF complexes of benzene, ethylene, and acetylene. Complex binding energies have been corrected for basis set superposition error, and zero point energy corrections have been done on Hartree–Fock binding energies. Computed results indicate that the complexes exist in different conformations and among them those with π-lithium and π-hydrogen bonds are the most stable. π-lithium bonds are stronger than π-hydrogen bonds. The computed binding energies and geometry of HF complexes correlate well with the available experimental …

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Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Cheettu Ammal, P. Venuvanalingam Jan 1998

Ab Initio And Dft Investigations Of Lithium/Hydrogen Bonded Complexes Of Trimethylamine, Dimethyl Ether And Dimethyl Sulfide, Salai Cheettu Ammal, P. Venuvanalingam

Faculty Publications

Ab initio and DFT computations have been carried out on LiF and HF complexes of a set of n-donors viz. trimethylamine, dimethyl ether and dimethyl sulfide with a 6-31++G(d,p) basis set. The effect of correlation has been included with MP2, MP4 and DFT calculations. NBO analyses of the wavefunctions have been performed to examine the intermolecular interaction at the orbital level. Calculations reveal that these donors form strong n→σ* complexes and computed binding energies of the (CH3)2O···HF complex agree very well with the experimental binding energies from IR spectroscopy. LiF forms stronger complexes than HF, …

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The Temperature Dependent Modification Of The Ca2+ Release Mechanism Of Skeletal Muscle Sarcoplasmic Reticulum, Shawn Patrick Mullen Dec 1997

The Temperature Dependent Modification Of The Ca2+ Release Mechanism Of Skeletal Muscle Sarcoplasmic Reticulum, Shawn Patrick Mullen

Dissertations and Theses

The Ca2+ release protein/ryanodine receptor from skeletal muscle sarcoplasmic reticulum is shown to be modulated in a unique manner by small changes in temperature. Thiol oxidants and reducing agents modify channel function in a biphasic manner at 40° C, while at 34° C the channel exhibits only a monophasic behavior. Elevated temperature appears to expose a second set of reactive groups that, when either oxidized or reduced, alter function. Previous studies have focused on the properties of the release mechanism at or below 37° C. This study shows that at 40° C, which more reflects the body temperature of …

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Aspects Of Postcollision Interactions (Pci) Near The Ar L-Shell, James A.R. Samson, Y. Lu, Wayne C. Stolte Oct 1997

Aspects Of Postcollision Interactions (Pci) Near The Ar L-Shell, James A.R. Samson, Y. Lu, Wayne C. Stolte

Chemistry and Biochemistry Faculty Research

In the present work we are interested in near-threshold photoionization experiments involving postcollision effects related to the Auger decay of a vacancy in the Ar L shell. In particular, we have measured the photoelectron energy spectrum resulting from the above postcollision interaction effects and have observed electrons produced by the process of electron capture and reemission.

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Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz Aug 1997

Spectroscopically Distinct Cobalt(Ii) Sites In Heterodimetallic Forms Of The Aminopeptidase From Aeromonas Proteolytica:  Characterization Of Substrate Binding, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The Co(II)Zn(II)- and Zn(II)Co(II)-substituted derivatives of the aminopeptidase from Aeromonas proteolytica (AAP) were probed by EPR spectroscopy. EPR spectra of the high-spin S = 3/2 Co(II) ions in [CoZn(AAP)] and [ZnCo(AAP)] indicated that each metal binding site provides a spectroscopically distinct signature. For [CoZn(AAP)], subtraction of EPR spectra recorded at pH 7.5 and 10 revealed that two species were present and that the relative contributions to each of the experimental spectra were pH-dependent. The first EPR species, predominant at lower pH values, was simulated as a relatively featureless axial signal with geff values of 2.20, 3.92, and …

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Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff Jul 1997

Nondipole Resonant X-Ray-Raman Spectroscopy: Polarized Inelastic Scattering At The K Edge Of Cl2, J. D. Mills, J. A. Sheehy, T. A. Ferrett, S. H. Southworth, R. Mayer, Dennis W. Lindle, P. W. Langhoff

Chemistry and Biochemistry Faculty Research

Experimental and theoretical studies are reported on the inelastic (Raman) scattering of wavelength-selected polarized x rays from the K edge of gas-phase chlorine molecules. The polarized emission spectra exhibit prominent nondipole features consequent of phase variations of the incident and emitted radiation over molecular dimensions, as predicted by the Kramers-Heisenberg scattering formalism. Issues pursuant to the detection of core-hole localization by resonant Raman scattering from homonuclear diatomic molecules are critically examined. [S0031-9007(97)03486-8]

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Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton Jun 1997

Calculation Of Electronic Coupling Matrix Elements For Ground And Excited State Electron Transfer Reactions: Comparison Of The Generalized Mulliken–Hush And Block Diagonalization Methods, Robert J. Cave, Marshall D. Newton

All HMC Faculty Publications and Research

Two independent methods are presented for the nonperturbative calculation of the electronic coupling matrix element (Hab) for electron transfer reactions using ab initio electronic structure theory. The first is based on the generalized Mulliken–Hush (GMH) model, a multistate generalization of the Mulliken Hush formalism for the electronic coupling. The second is based on the block diagonalization (BD) approach of Cederbaum, Domcke, and co-workers. Detailed quantitative comparisons of the two methods are carried out based on results for (a) several states of the system Zn2OH2+ and (b) the low-lying states of the benzene–Cl atom complex and its contact ion pair. Generally …

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Computer Modeling Of Molecular Vibration Frequencies And Its Application To The Modeling Of Silane Compounds, Ryan T. Merrell May 1997

Computer Modeling Of Molecular Vibration Frequencies And Its Application To The Modeling Of Silane Compounds, Ryan T. Merrell

Honors Capstone Projects and Theses

No abstract provided.

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Epr Studies On The Mono- And Dicobalt(Ii)-Substituted Forms Of The Aminopeptidase From Aeromonas Proteolytica. Insight Into The Catalytic Mechanism Of Dinuclear Hydrolases, Brian Bennett, Richard C. Holz Feb 1997

Epr Studies On The Mono- And Dicobalt(Ii)-Substituted Forms Of The Aminopeptidase From Aeromonas Proteolytica. Insight Into The Catalytic Mechanism Of Dinuclear Hydrolases, Brian Bennett, Richard C. Holz

Physics Faculty Research and Publications

The structure and function of the prototypical dinuclear hydrolase, namely, the aminopeptidase from Aeromonas proteolytica (AAP), was probed by EPR spectroscopy of the mono- and dicobalt(II)-substituted derivatives. A new systematic protocol for the interpretation of Co(II) EPR spectra is described and the S = 3/2 spin states of the Co(II)-substituted forms of the enzyme have been characterized. This protocol allows the simulation of line shape using theoretically allowed geff values corresponding to an isotropic greal value. In addition, the gross distortion of EPR spectra of high-spin S = 3/2 Co(II) ions has been investigated, …

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Semiclassical Approach To The Hydrogen-Exchange Reaction Reactive And Transition-State Dynamics, Sophya V. Garashchuk, F. Grossmann, D. Tannor Jan 1997

Semiclassical Approach To The Hydrogen-Exchange Reaction Reactive And Transition-State Dynamics, Sophya V. Garashchuk, F. Grossmann, D. Tannor

Faculty Publications

Scattering matrix elements and symmetric transition-state resonances for the collinear H 2 + H → H + H 2 reaction are obtained using a time-dependent approach. The correlation function between reactant channel wavepackets and product channel wavepackets is used to determine the S-matrix elements. In a similar fashion, autocorrelation functions are used to extract the positions and widths of transition-state resonances. The time propagation of the wavepackets is performed by the improved semiclassical frozen Gaussian method of Herman and Kluk, which is an initial value, uniformly converged method. The agreement between the quantum and semiclassical results is far better …

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Lithium Bonding Interaction In H2Cy⋯Lif (Y=O,S) Complexes: A Theoretical Probe, Salai Cheettu Ammal, P. Venuvanalingam, S. Pal Jan 1997

Lithium Bonding Interaction In H2Cy⋯Lif (Y=O,S) Complexes: A Theoretical Probe, Salai Cheettu Ammal, P. Venuvanalingam, S. Pal

Faculty Publications

Ab initio calculations at 6-31++G(d,p) level have been done on H2CY⋯LiF (Y=O,S) complexes choosing ten possible orientations in each complex. The effect of correlation on complex binding energies has been studied via single point MP2 (full) calculations done on 6-31++G(d,p) geometry. Binding energies have been corrected for basis set superposition error. Frequency calculations confirm that H2CO⋯LiF and H2CS⋯LiF complexes have three and two stable forms, respectively. The most stable form in each complex has been found to have a strong lithium bonding interaction and a secondary hydrogen bondinginteraction. NBO analysis has revealed that in this form oxygen donates nσ lone …

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Cross Sections For The Production Of He+ (Np) 2p0 States By 50 To 150 Kev Proton Impact On Helium, Wayne C. Stolte, R. Bruch Sep 1996

Cross Sections For The Production Of He+ (Np) 2p0 States By 50 To 150 Kev Proton Impact On Helium, Wayne C. Stolte, R. Bruch

Chemistry and Biochemistry Faculty Research

Cross sections have been measured for the production of He+ (np) 2Po states, n=2,3,4, by proton impact on helium over a projectile velocity range of 1.42–2.45 a.u. (50 ≤E≤150 keV). Cross sections were determined by measuring the extreme ultraviolet photons emitted from excited He1 ions. The data indicate a lower energy than expected for the maximum cross section. A comparison of the present results in terms of projectile energy dependance with the cross sections for excitation to He (1snp) 1Po, ionization, and total electron capture suggests the primary mechanism …

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Post-Collision Interactions In The Auger Decay Of The Ar L-Shell, James A.R. Samson, Wayne C. Stolte, Z. X. He, J. N. Cutler, D. Hansen Sep 1996

Post-Collision Interactions In The Auger Decay Of The Ar L-Shell, James A.R. Samson, Wayne C. Stolte, Z. X. He, J. N. Cutler, D. Hansen

Chemistry and Biochemistry Faculty Research

The photoionization cross sections for Ar+ through Ar4+, produced by the Auger decay of a 2p hole in argon, have been measured between 242 eV and 253 eV by the use of synchrotron radiation. The high resolution of the monochromator has allowed a detailed study of the postcollision interactions that occur in this spectral region. The concept of photoelectron recapture by Ar2+ to produce the Ar+ continuum is studied. The relative values of the quantum-mechanical calculations of the photoelectron recapture probability are shown to be in excellent agreement with the present data. The magnitude …

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The Structure Of Alkali Halide Dimers: A Critical Test Of Ionic Models And New Ab Initio Results, T. Törring, S. Biermann, J. Hoeft, Richard J. Mawhorter, Robert J. Cave, C. Szemenyei May 1996

The Structure Of Alkali Halide Dimers: A Critical Test Of Ionic Models And New Ab Initio Results, T. Törring, S. Biermann, J. Hoeft, Richard J. Mawhorter, Robert J. Cave, C. Szemenyei

All HMC Faculty Publications and Research

In semiempirical ionic models a number of adjustable parameters have to be fitted to experimental data of either monomer molecules or crystals. This leads to strong correlations between these constants and prevents a unique test and a clear physical interpretation of the fit parameters. Moreover, it is not clear whether these constants remain unchanged when the model is applied to dimers or larger clusters. It is shown that these correlations can be substantially reduced when reliable information about dimers is available from experiments or ab initio calculations. Starting with Dunham coefficients of the monomer potential determined from microwave measurements, we …

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Evidence Favoring Molybdenum−Carbon Bond Formation In Xanthine Oxidase Action: 17O- And 13C-Endor And Kinetic Studies, Barry D. Howes, Robert C. Bray, Raymond L. Richards, Nigel A. Turner, Brian Bennett, David J. Lowe Feb 1996

Evidence Favoring Molybdenum−Carbon Bond Formation In Xanthine Oxidase Action: 17O- And 13C-Endor And Kinetic Studies, Barry D. Howes, Robert C. Bray, Raymond L. Richards, Nigel A. Turner, Brian Bennett, David J. Lowe

Physics Faculty Research and Publications

The reaction mechanism of the molybdoenzyme xanthine oxidase has been further investigated by 13C and 17O ENDOR of molybdenum(V) species and by kinetic studies of exchange of oxygen isotopes. Three EPR signal-giving species were studied:  (i) Very Rapid, a transient intermediate in substrate turnover, (ii) Inhibited, the product of an inhibitory side reaction with aldehyde substrates, and (iii) Alloxanthine, a species formed by reaction of reduced enzyme with the inhibitor, alloxanthine. The Very Rapid signal was developed either with [8-13C]xanthine or with 2-oxo-6-methylpurine using enzyme equilibrated with [17O]H2O. The Inhibited signal was …

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Design And Performance Of The Advanced-Light-Source Double-Crystal Monochromator, G. Jones, S. Ryce, Dennis W. Lindle, B. A. Karlin, J. C. Woicik, Rupert C. Perera Feb 1995

Design And Performance Of The Advanced-Light-Source Double-Crystal Monochromator, G. Jones, S. Ryce, Dennis W. Lindle, B. A. Karlin, J. C. Woicik, Rupert C. Perera

Chemistry and Biochemistry Faculty Research

A new “Cowan type” double-crystal monochromator, based on the boomerang design used at National Synchrotron Light Source (NSLS) beamline X-24A, has been developed for beamline 9.3.1 at the Advanced Light Source (ALS), a windowless ultrahigh vacuum beamline covering the 1-6 keV photon-energy range. Beamline 9.3.1 is designed to simultaneously achieve the goals of high energy resolution, high flux, and high brightness at the sample. The mechanical design of the monochromator has been simplified, and recent developments in technology have been included. Measured mechanical precision of the monochromator shows significant improvement over existing designs. In tests with x-rays at NSLS beamline …

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High-Brightness Beamline For X-Ray Spectroscopy At The Advanced Light Source, Rupert C. Perera, G. Jones, Dennis W. Lindle Feb 1995

High-Brightness Beamline For X-Ray Spectroscopy At The Advanced Light Source, Rupert C. Perera, G. Jones, Dennis W. Lindle

Chemistry and Biochemistry Faculty Research

Beamline 9.3.1 at the Advanced Light Source (ALS) is a windowless beamline, covering the 1-6 keV photon-energy range, designed to achieve the goals of high energy resolution, high flux, and high brightness at the sample. When completed later this year, it will be the first ALS monochromatic hard-x-ray beamline, and its brightness will be an order-of-magnitude higher than presently available in this energy range. In addition, it will provide flux and resolution comparable to any other beamline now in operation. To achieve these goals, two technical improvements, relative to existing x-ray beamlines, were incorporated. First, a somewhat novel optical design …

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Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra Nov 1994

Three-Body Analytical Potential For Interacting Helium Atoms, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

Large basis set ab initio calculations have been carried out for a dense grid of points on the He, potential energy surface. Three-body contributions were extracted at every point, and a number of concise functional representations for the three-body potential surface were then examined. Three-body multipolar dispersion terms and other radial and angular terms were used in the representations, and an assessment of relative importance of the different terms is presented. Combined with a two-body He-He potential, the results of this work should offer a high quality interaction potential for simulations of aggregated helium.

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Feasibility Of Using Ultrasonic Cavitation To Produce Silica Sol, Gary L. Vines Mar 1994

Feasibility Of Using Ultrasonic Cavitation To Produce Silica Sol, Gary L. Vines

Honors Capstone Projects and Theses

No abstract provided.

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The Modeling Of Phosphorus Dynamics In A Lake System, Todd N. Swift Jan 1994

The Modeling Of Phosphorus Dynamics In A Lake System, Todd N. Swift

Presidential Scholars Theses (1990 – 2006)

We have constructed a basic closed stock and flow model of lake phosphorus cycling that includes three stock concentrations: inorganic phosphorus, phosphorus in living organic material, and phosphorus in dead organic material. Stocks are connected by flows that are made stock dependent in a plausible manner. The model exhibits two equilibrium points, one stable and the other unstable, with an interesting crossover between them. Below a certain total phosphorus threshold, stable equilibrium is characterized by all of the phosphorus stock residing in the inorganic form, suggesting the collapse of the biological system. Above the threshold, this is not true. We …

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A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Mixed Alkali Halide Dimers, Robert J. Cave, Ian Ono '94 Dec 1993

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Mixed Alkali Halide Dimers, Robert J. Cave, Ian Ono '94

All HMC Faculty Publications and Research

Results are presented from ab initio calculations on several mixed alkali halide dimers made up of Li, Na, F, and Cl. All of the dimers are investigated at the restricted Hartree–Fock level to provide ab initio estimates of geometries, vibrational frequencies, and binding energies. The dimer LiNaF2 is then treated using a variety of basis sets at the Hartree–Fock level, as well as at correlated levels (second‐order Møller–Plesset and coupled‐cluster singles and doubles) to examine the sensitivity of the calculations to use of higher levels of theory. The results are then compared to the experimental data available for the LiNaF2 …

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Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry Nov 1993

Response To "Comment On 'The Weakest Bond: Experimental Observation Of Helium Dimer'", Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, Ronald Gentry

Peer Reviewed Articles

No abstract provided.

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Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry Mar 1993

Influence Of Retardation On The Vibrational Wave Function And Binding Energy Of The Helium Dimer, Fei Luo, Geunsik Kim, George C. Mcbane, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Because of the extremely small binding energy of the helium dimer, the nuclear wave function is delocalized over an extremely large range of separations. One might therefore expect the properties of this extraordinary species to be sensitive to the potential at very large internuclear distances, r, where relativistic corrections to the usual van der Waals interaction may be important. We have estimated the effect of retardation, which changes the r-6 dependence of the potential to r-7 in the limit of large r, and have found that the binding energy and expectation value (r) are …

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Angular Distributions For Near-Threshold (E,2E) Processes For Li And Mg, Cheng Pan, Anthony F. Starace Mar 1993

Angular Distributions For Near-Threshold (E,2E) Processes For Li And Mg, Cheng Pan, Anthony F. Starace

Anthony F. Starace Publications

Distorted-wave calculations of the triply differential cross sections for electron-impact ionization of Li and Mg are presented for the coplanar, θ12=π geometry in which the final-state electrons share 2 eV of excess energy equally. Our theoretical approach, described in detail elsewhere [C. Pan and A. F. Starace, Phys. Rev. A 45, 4588 (1992)], employs a partial-wave expansion of initial- and final-state wave functions, treats direct and exchange interactions of initial and final electrons with the target core, and treats the final-state interaction between the two continuum electrons by a screening potential. Li and Mg targets are found to …

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A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Alkali Halide Dimers, Robert P. Dickey '93, David Maurice '91, Robert J. Cave, Richard J. Mawhorter Feb 1993

A Theoretical Investigation Of The Geometries, Vibrational Frequencies, And Binding Energies Of Several Alkali Halide Dimers, Robert P. Dickey '93, David Maurice '91, Robert J. Cave, Richard J. Mawhorter

All HMC Faculty Publications and Research

Results are presented from ab initio calculations on the symmetrical alkali halide dimers made up of Li, Na, K, F, and Cl. We examine the sensitivity of representative monomer and dimer geometries to the variation of the basis set with and without polarization and diffuse functions. The geometries are then compared with available experimental results. We have also calculated vibrational frequencies at the restricted Hartree–Fock level and examined the changes in geometry brought about by correlation using second‐order Møller–Plesset perturbation theory. It is found that Hartree–Fock theory in a modest basis set with diffuse and polarization functions yields results comparable …

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Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra Jan 1993

Pairwise And Many-Body Contributions To Interaction Potentials In He(N) Clusters, Carol A. Parish, Clifford E. Dykstra

Chemistry Faculty Publications

High level ab initio calculations have been carried out to assess the pairwise additivity of potentials in the attractive or well regions of the potential surfaces of clusters of helium atoms. A large basis set was employed and calculations were done at the Brueckner orbital coupled cluster level. Differences between calculated potentials for several interacting atoms and the corresponding summed pair potentials reveal the three‐body and certain higher order contributions to the interaction strengths. Attraction between rare gas atoms develops from dispersion, and so helium clusters provide the most workable systems for analyzing nonadditivity of dispersion. The results indicate that …

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High-Energy Behavior Of The Double Photoionization Of Helium From 2 To 12 Kev, Jon C. Levin, Ivan A. Sellin, B. M. Johnson, Dennis W. Lindle, R. D. Miller, Y. Azuma, H. G. Berry, D.-H. Lee, N. Berrah Jan 1993

High-Energy Behavior Of The Double Photoionization Of Helium From 2 To 12 Kev, Jon C. Levin, Ivan A. Sellin, B. M. Johnson, Dennis W. Lindle, R. D. Miller, Y. Azuma, H. G. Berry, D.-H. Lee, N. Berrah

Chemistry and Biochemistry Faculty Research

We report the ratio of double-to-single photoionization of He at several photon energies from 2 to 12 keV. By time-of-Aight methods, we find a ratio consistent with an asymptote at 1.5%±0.2%, essentially reached by h v≈4 keV. Fair agreement is obtained with older shake calculations of Byron and Joachain [Phys. Rev. 164, 1 (1967)], of Aberg [Phys. Rev. A 2, 1726 (1970)], and with recent many-body perturbation theory (MBPT) of Ishihara, Hino, and McGuire [Phys. Rev. A 44, 6980 (1991)]. The result lies below earlier MPBT calculations by Amusia et al. [J. Phys. B 8 …

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The Weakest Bond: Experimental Observation Of Helium Dimer, Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, W. Ronald Gentry Dec 1992

The Weakest Bond: Experimental Observation Of Helium Dimer, Fei Luo, George C. Mcbane, Geunsik Kim, Clayton F. Giese, W. Ronald Gentry

Peer Reviewed Articles

Helium dimer ion was observed after electron impact ionization of a supersonic expansion of helium with translational temperature near 1 mK. The dependence of the ion signal on source pressure, distance from the source, and electron kinetic energy was measured. The signal was determined to arise from ionization of neutral helium dimer.

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