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Atomic, Molecular and Optical Physics Commons™

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1993

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Articles 1 - 16 of 16

Full-Text Articles in Atomic, Molecular and Optical Physics

Infrared Fluorescence Studies Of Electronic-To-Vibrational Energy Transfer In A Br2:No System, Michael R. Hawks Dec 1993

Infrared Fluorescence Studies Of Electronic-To-Vibrational Energy Transfer In A Br2:No System, Michael R. Hawks

Theses and Dissertations

Steady-state photolysis techniques were used to study electronic-to- vibrational energy transfer mechanisms from atomic bromine to nitric oxide. Molecular bromine was photodissociated by 488nm radiation to produce equal parts Br(2P1/2) and Br(2P3/2). Side fluorescence intensity from Br(2P1/2) at 2.7 µm and from NO (v=1 and 2) around 5.3 µm measured as a function of bromine pressure and nitric oxide pressure. The branching ratio collisional transfer into the first and second states of NO was determined, and previously reported rates for quenching of NO by molecular bromine were verified.

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High Resolution Fourier Transform Absorption Spectrum Of 79Br2 B3Π(0U+) ← X1ΣG+, Robert E. Franklin Dec 1993

High Resolution Fourier Transform Absorption Spectrum Of 79Br2 B3Π(0U+) ← X1ΣG+, Robert E. Franklin

Theses and Dissertations

High Resolution Fourier Transform Spectroscopy has been conducted for the 79Br2 B3π(0u+) ← X1Σg+ system of 79Br2. A total of 64 vibrational levels, including v"= 0-3 and v' = 10-33, have been observed and assigned. Rotational levels as high as J=76 were observed. A global fitting routine has been developed to fit the rotational spectra to the Dunham Expansion. Using Bv and Dv for both the X and B state, rotational transitions were calculated to within 0. 02 cm-1. The expansions of …

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Hyperspectral Analysis Of Space Objects: Signal To Noise Evaluation, Daniel Hrovat Dec 1993

Hyperspectral Analysis Of Space Objects: Signal To Noise Evaluation, Daniel Hrovat

Theses and Dissertations

Hyperspectral analysis of space objects is being considered as a means of enhancing Space Object Identification. SOI capabilities. This study develops a mathematical simulation based on fundamental radiometry principles to evaluate the feasibility of hyperspectral analysis of space objects. The study uses Signal to Noise Ratio SNR as the basis for the feasibility evaluation, and addresses the question Is there enough target signal in narrow wavelength bandwidths to conduct hyperspectral measurements of space objects The analysis characterizes the target signal and noise sources using fundamental radiometry, and develops a flexible radiometry model which calculates the target signal count rate, and …

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Vibrational Energy Transfer Within The B3Π(0+U) State Of 79Br2 Upon Collision With N2, O2, No, And Sf6, Gregory S. Williams Dec 1993

Vibrational Energy Transfer Within The B3Π(0+U) State Of 79Br2 Upon Collision With N2, O2, No, And Sf6, Gregory S. Williams

Theses and Dissertations

Vibrational transfer and electronic quenching in the lower vibrational levels of the 79Br2(B; v'≤3) were investigated using spectrally resolved, temporally resolved pulsed laser induced fluorescence techniques. Spectrally resolved emissions from collisionally populated Br2(B) vibrational levels were observed for N2, O2, NO, and SF6collision partners. The vibrational transfer was efficient in the nonpredissociative vibrational levels and is adequately described by the Montroll-Shuler model. An average fundamental vibrational transfer rate coefficient of kv(l,0)=3.4(±0.6) x 10-11 cm3/molec-sec predicts the vibrational transfer rates for the 0≤v'≤3 collisions with …

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Observation Of Non-Isotropic Auger Angular Distribution In The C(1s) Shape Resonance Of Co, Oliver Hemmers, Franz Heiser, J. Eiben, R. Wehlitz, U. Becker Aug 1993

Observation Of Non-Isotropic Auger Angular Distribution In The C(1s) Shape Resonance Of Co, Oliver Hemmers, Franz Heiser, J. Eiben, R. Wehlitz, U. Becker

Environmental Studies Faculty Publications

Angle-resolved high-resolution C(KVV) Auger spectra of CO were taken in the vicinity of the C(1s) σ* shape resonance. These spectra show clear evidence for the theoretically predicted anisotropic K-shell Auger emission in molecules. Complementary results from angle-resolved photoion spectroscopy show that the small size of the observed effect is, besides the varying intrinsic anisotropy of the Auger decay, also due to a smaller anisotropy in the primary absorption process than originally predicted but in good agreement with more recent calculations. Contrary to this, satellite Auger transitions show unexpectedly large anisotropies.

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Orientational Phase Transition In Na_{X}C_{60} (1, T. Yildirim, J. E. Fischer, A. B. Harris, Peter W. Stephens, Dengfa Liu, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii Aug 1993

Orientational Phase Transition In Na_{X}C_{60} (1, T. Yildirim, J. E. Fischer, A. B. Harris, Peter W. Stephens, Dengfa Liu, Laurent Brard, Robert M. Strongin, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

X-ray diffraction and calorimetry data on cubic NaxC60(1<x60, e.g., Tm(x=1.3)=325 K. The ordered phases are the same as in pure C60: simple cubic, space group Pa3¯, but the orientations in the disordered phase are more restricted. We explain how Na stabilizes the ordered phase to rather high T, while K and Rb do not, in terms of Coulomb interactions between C60 molecules and and Na ions which we calculate from the local charge density of C60.

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Design And Construction Of A Lithium Vapor Oven, Corey A. Leon Jul 1993

Design And Construction Of A Lithium Vapor Oven, Corey A. Leon

Honors Theses

A lithium vapor oven to be used as a source of lithium target atoms in atomic collision experiments was designed and constructed. The oven was installed in the beamline of the Van de Graaff accelerator at Western Michigan University. Test results indicated the oven produced a diffuse cloud of evaporated lithium instead of the intended concentrated jet spray. Recommendations concerning the design are made for future efforts.

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Self-Consistent Determination Of Electronic Structure And Elementary Excitations Of Finite Modulation-Doped Superlattices, Roger H. Yu Jun 1993

Self-Consistent Determination Of Electronic Structure And Elementary Excitations Of Finite Modulation-Doped Superlattices, Roger H. Yu

All Faculty Scholarship for the College of the Sciences

A self-consistent framework for the study of the electronic level structure of finite superlattices has been proposed. One of the surface states (Tamm states) found in our calculation crosses the Fermi energy in the energy gap when the depletion effect near the surface increases. We have shown the existence of low-energy Tamm states in our calculation when the surface barrier is lower than that of the interior. The electronic excitations of the superlattice have been studied via the electron-energy-loss function within the random-phase approximation. Two plasmon modes (well above the phonon response frequency) due to the Tamm states have also …

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Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston Mar 1993

Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston

Theses and Dissertations

This investigation designed and developed a miniature gas chromatograph (GC) using silicon micromachining techniques. The GC is composed of a miniature sample injector (10 µl sample loop); a 0.9 m long, rectangular-shaped (300 µm width and 10 micrometers height) capillary column coated with a 0.2 µm thick copper phthalocyanine (CuPc) stationary phase; and a dual-detector scheme incorporating a CuPc-coated chemiresistor and a 125 µm diameter thermal conductivity detector bead. Micromachining was employed to fabricate the sample injector interface, the GC column, and the dual-detector cavity. A novel processing technique was developed to sublime the CuPc stationary phase coating on the …

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Multiplet-Changing Auger Transitions In Valence Double Photoionization, U. Becker, Oliver Hemmers, B. Langer, I. Lee, A. Menzel, R. Wehlitz, M. Ya Amusia Feb 1993

Multiplet-Changing Auger Transitions In Valence Double Photoionization, U. Becker, Oliver Hemmers, B. Langer, I. Lee, A. Menzel, R. Wehlitz, M. Ya Amusia

Environmental Studies Faculty Publications

The decay of valence satellite states in neon above the first double-ionization threshold has been studied experimentally and theoretically. Special emphasis was given to differentiate between two decay modes: valence Auger and valence-multiplet Auger decay. It is shown that the latter process is predominant in the low kinetic energy part of the spectrum. The main structures of this low-energy Auger spectrum could be designated by help of calculated transition energies and decay rates.

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Measurement Of The Casimir-Polder Force, C. I. Sukenik, M. G. Boshier, S. Cho, V. Sandoghdar, E. A. Hinds Feb 1993

Measurement Of The Casimir-Polder Force, C. I. Sukenik, M. G. Boshier, S. Cho, V. Sandoghdar, E. A. Hinds

Physics Faculty Publications

The authors have studied the deflection of ground-state sodium atoms passing through a micron-sized parallel-plate cavity by measuring the intensity of a sodium atomic beam transmitted through the cavity as a function of cavity plate separation. This experiment provides clear evidence for the existence of the Casimir-Polder force, which is due to modification of the ground-state Lamb shift in the confined space of a cavity. The results confirm the magnitude of the force and the distance dependence predicted by quantum electrodynamics.

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Temporal Development Of Electric Field Structures In Photoconductive Gaas Switches, K. H. Schoenbach, J. S. Kenney, F.E. Peterkin, R. J. Allen Jan 1993

Temporal Development Of Electric Field Structures In Photoconductive Gaas Switches, K. H. Schoenbach, J. S. Kenney, F.E. Peterkin, R. J. Allen

Bioelectrics Publications

The temporal development of the electric field distribution in semi‐insulating GaAs photoconductive switches operated in the linear and lock‐on mode has been studied. The field structure was obtained by recording a change in the absorption pattern of the switch due to the Franz–Keldysh effect at a wavelength near the band edge of GaAs. In the linear mode, a high field layer develops at the cathode contact after laser activation. With increasing applied voltage, domainlike structures become visible in the anode region and the switch transits into the lock‐on state, a permanent filamentary electrical discharge. Calibration measurements show the field intensity …

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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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Determination Of The Neutron Spin Structure Function, P. L. Anthony, R. G. Arnold, H. R. Band, H. Borel, P.E. Bosted, V. Breton, G. D. Cates, T. E. Chupp, F. S. Dietrich, J. Dunne, R. Erbacher, J. Fellbaum, H. Fonvielle, R. Gearhart, R. Holmes, E. W. Hughes, J. R. Johnson, D. Kawall, C. Keppel, S. E. Kuhn, R. M. Lombard-Nelsen, J. Marroncle, T. Maruyama, W. Meyer, Z. E. Meziani, H. Middleton, J. Morgenstern, N. R. Newbury, G. G. Petratos, R. Pitthan, R. Prepost, Y. Roblin, S. E. Rock, S. H. Rokni, G. Shapiro, T. Smith, P. A. Souder, M. Spengos, F. Staley, L. M. Stuart, Z. M. Szalata, Y. Terrien, A. K. Thompson, J. L. White, M. Woods, J. Xu, C. C. Young, G. Zapalac, E142 Collaboration Jan 1993

Determination Of The Neutron Spin Structure Function, P. L. Anthony, R. G. Arnold, H. R. Band, H. Borel, P.E. Bosted, V. Breton, G. D. Cates, T. E. Chupp, F. S. Dietrich, J. Dunne, R. Erbacher, J. Fellbaum, H. Fonvielle, R. Gearhart, R. Holmes, E. W. Hughes, J. R. Johnson, D. Kawall, C. Keppel, S. E. Kuhn, R. M. Lombard-Nelsen, J. Marroncle, T. Maruyama, W. Meyer, Z. E. Meziani, H. Middleton, J. Morgenstern, N. R. Newbury, G. G. Petratos, R. Pitthan, R. Prepost, Y. Roblin, S. E. Rock, S. H. Rokni, G. Shapiro, T. Smith, P. A. Souder, M. Spengos, F. Staley, L. M. Stuart, Z. M. Szalata, Y. Terrien, A. K. Thompson, J. L. White, M. Woods, J. Xu, C. C. Young, G. Zapalac, E142 Collaboration

Physics Faculty Publications

The spin structure function of the neutron g1n has been determined over the range 0.03 < x < 0.6 at an average Q2 of 2 (GeV/c)2 by measuring the asymmetry in deep inelastic scattering of polarized electrons from a polarized 3He target at energies between 19 and 26 GeV. The integral of the neutron spin structure function is found to be f-10 gn1(x)dx = -0.022 ± 0.011. Earlier reported proton results together with the Bjorken sum rule predict f-10 gn1(x)dx = -0.059 ± 0.019.

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A Study Of Molecular Order And Motion In Nematic Liquid Crystal Mixtures, Jon Michael Goetz Jan 1993

A Study Of Molecular Order And Motion In Nematic Liquid Crystal Mixtures, Jon Michael Goetz

Dissertations, Theses, and Masters Projects

Materials which flow like fluids, but possess anisotropic properties like molecular crystals, are called 'liquid crystals'. Studies of liquid crystals contribute to our understanding of how molecular orientation influences macroscopic properties. This thesis presents experimental and theoretical investigations of molecular order and dynamics in nematic liquid crystal systems. First, deuterium nuclear magnetic resonance is used to determine the degree of orientational order of both components of a liquid crystal mixture simultaneously. The temperature dependence of the four order parameters is interpreted using a newly developed mean field theory of nematic binary mixtures composed of biaxial molecules. Next, mean field theory …

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Photoabsorption Spectra Of Hydrogen In Magnetic Fields, John A. Shaw Jan 1993

Photoabsorption Spectra Of Hydrogen In Magnetic Fields, John A. Shaw

Dissertations, Theses, and Masters Projects

Measurements of the absorption spectrum of atomic H in strong magnetic fields have been analyzed. The measurements, performed by the Bielefeld, Germany experimental group, investigated the photoabsorption to levels near the ionization threshold in magnetic fields ranging from 2.7 to 6 Tesla. Taking advantage of a classical scaling law, the photon energy and the magnetic field strength were varied simultaneously in the experiment and the absorption rate vs. B{dollar}\sp{lcub}-1/3{rcub}{dollar} at fixed scaled-energy, {dollar}\varepsilon{dollar} = E/(B/B{dollar}\sb{lcub}\rm o{rcub})\sp{lcub}2/3{rcub}{dollar} was measured. The absorption rate was observed to exhibit sinusoidal fluctuations which we correlate with closed classical orbit of the electron. A Fourier transformation …

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