Regional Stratigraphic Framework of Surficial Sediments and Bedrock Beneath Lake Ontario

Approximately 2550 km of single-channel high-resolution seismic reflection profiles have been interpreted and calibrated with lithological and geochronological information from four representative piston cores and one grab sample to provide a regional stratigraphie framework for the subbottom deposits of Lake Ontario. Five units overlying Paleozoic bedrock were identified and mapped. These are classified as informal units and represent, from oldest to youngest: (A) subglacial till (?) deposited by the Port Huron ice at the end of the Wisconsin glaciation; (B) an ice-marginal (?) unit confined to the western part of the lake that was probably deposited during retreat of the Port Huron ice shortly after 13 ka; (C) a regionally extensive unit of laminated glacio-lacustrine clay that accumulated until about 11 ka; (D) a weakly laminated to more massive lake clay deposited during a period of reduced water supply and rising water levels after the drawdown of the high-level glacial lakes (Iroquois and successors); and (E) modern lake clay less than 10 m thick that began accumulating around 6-8 ka with the subsequent return of upper Great Lakes drainage through the Ontario basin. Seismic reflections also define the configuration of the bedrock surface and pre-glacial stream valleys incised in the bedrock surface. Several anomalous bottom and subbottom features in the surficial sediments are mapped, such as discontinuous and offset reflections, furrows, gas pockets, and areas of large subbottom relief. None of these features appear to be spatially correlative with the diffuse seismicity that characterizes the lake area or with deeper structures such as Paleozoic bedrock faults or crustal-penetrating faults in the Precambrian basement.On a interprété et étalonné environ 2550 km de profils de sismique réflexion monocanal à haute résolution selon les données lithologiques et géochronologique de quatre sondages représentatifs faits par carottier à piston et un échantillon prélevé avec une benne afin d'établir le cadre stratigraphique des dépôts accumulés sous le fond du lac Ontario. Cinq unités recouvrant le substratum paiéozoïque ont été identifées et cartographiées. Ces unités informelles, de la plus ancienne à la plus jeune, sont : (A) un till sous-glaciaire (?) déposé par les glaces de Port Huron à la fin de la glaciation wisconsienne; (B) une unité de limite glaciaire (?) confinée à la partie ouest du lac et qui a probablement été déposée pendant le retrait des glaces de Port Huron, peu après 13 ka; (C) une unité d'étendue régionale d'argile glaciolacustre feuilletée qui s'est accumulée jusqu'à environ 11 ka; (D) une argile lacustre, de faiblement feuilletée à massive, mise en place au cours d'une période où il y eut approvisionnement en eau réduit et hausse du niveau de l'eau après l'abaissement des lacs glaciaires (Iroquois et ultérieurs); et (E) une argile lacustre moderne de moins de 10 m d'épaisseur qui a commencé à s'accumuler à partir de 6-8 ka après la reprise du drainage des Grands Lacs par le bassin Ontario. La sismique réflexion a aussi permis de délimiter la configuration de la surface du socle et des vallées pré-glaciaires qui y sont entaillées. Plusieurs éléments des sédiments de surface du fond du lac et sous le fond ont été cartographies, comme des réflexions de discontinuités et de décalages, des rainures, des poches de gaz et des zones de grandes formes enfouies. Aucun de ces éléments ne semble correspondre spatialement à la sis-micité diffuse qui caractérise la région du lac ou aux structures profondes comme les failles de substratum paiéozoïque ou celle du socle précambrien.Ungefàhr 2550 km seismischer Reflexionsprofile wurden interpretiert und kalibiriert mit lithologischen und geochronologischen Informationen von vier repràsentativen Kolbenbohrkernen und einer ausges-chùrften Probe, um den regionalen stratigraphischen Rahmen fur die unter dem Bett des Ontariosees gelegenen Ablagerungen zu erhalten. Man hat fùnf Einheiten, die das anstehende Gestein aus dem Palàozoikum ùberlagern, identifiziert und kartographiert: (A) eine subglaziale Grundmoràne (?), die durch das Eis von Port Huron am Ende der Wisconsin-Vereisung abgelagert wurde; (B) eine auf den westlichen Teil des Sees begrenzte Eisrand (?)-Einheit, die wahrs-cheinlich wàhrend des Rùckzugs des Port Huron-Eises kurz nach 13ka abgelagert wurde; (C) eine regional ausgedehnte Einheit von blâttrigem glaziallimnischem Lehm, die sien bis etwa 11 ka ansammelte, (D) ein schwachbis massivblàttriger Seelehm, der wàhrend einer Période verminderter Wasserzufuhr und steigenden Wasserspiegeln sich ansammelte; und (E) moderner Seelehm von weniger als 10 m Dicke, der sich um etwa 6-8 ka anzusammeln begann, mit der Rùckkehr der Drainage der oberen GroRen Seen durch das Ontariobecken. Seismische Reflexionen las-sen auch die Konfiguration der Sockeloberflàche und der pràglazialen in die Sockeloberflàche eingeschnittenen FluBtàler erkennen. Mehrere unregelmàfîige Grundund Untergrunderscheinungen der Oberflàchensedimente wurden kartographiert, wie Diskontinuitàt und Hôhenunschiede der Reflexionen, Mulden, Gastaschen und Gebiete mit breitem Untergrundrelief. Keine dieser Erscheinungen scheint ràumlich mit der fur das Seen-Gebiet charakteristischen Seismik zu korrelieren oder mit tieferen Strukturen, wie die Verwerfungen des anstehenden Gestems aus dem Palàozoikum order durch die Kruste dringende Verwergungen im pràkambrischen Untergrund

Quantum Dot Potentials: Symanzik Scaling, Resurgent Expansions and Quantum Dynamics

This article is concerned with a special class of the ``double-well-like'' potentials that occur naturally in the analysis of finite quantum systems. Special attention is paid, in particular, to the so-called Fokker-Planck potential, which has a particular property: the perturbation series for the ground-state energy vanishes to all orders in the coupling parameter, but the actual ground-state energy is positive and dominated by instanton configurations of the form exp(-a/g), where a is the instanton action. The instanton effects are most naturally taken into account within the modified Bohr-Sommerfeld quantization conditions whose expansion leads to the generalized perturbative expansions (so-called resurgent expansions) for the energy values of the Fokker-Planck potential. Until now, these resurgent expansions have been mainly applied for small values of coupling parameter g, while much less attention has been paid to the strong-coupling regime. In this contribution, we compare the energy values, obtained by directly resumming generalized Bohr-Sommerfeld quantization conditions, to the strong-coupling expansion, for which we determine the first few expansion coefficients in powers of g^(-2/3). Detailed calculations are performed for a wide range of coupling parameters g and indicate a considerable overlap between the regions of validity of the weak-coupling resurgent series and of the strong-coupling expansion. Apart from the analysis of the energy spectrum of the Fokker-Planck Hamiltonian, we also briefly discuss the computation of its eigenfunctions. These eigenfunctions may be utilized for the numerical integration of the (single-particle) time-dependent Schroedinger equation and, hence, for studying the dynamical evolution of the wavepackets in the double-well-like potentials.Comment: 13 pages; RevTe

Nonstationary Collisional Dynamics in Determining Nitric Oxide Laser-Induced Flourescence Spectra

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77237/1/AIAA-8783-947.pd

Modified two-potential approach to tunneling problems

One-body quantum tunneling to continuum is treated via the two-potential approach, dividing the tunneling potential into external and internal parts. We show that corrections to this approach can be minimized by taking the separation radius inside the interval determined by simple expressions. The resulting two-potential approach reproduces the resonance energy and its width, both for narrow and wide resonances. We also demonstrate that, without losing its accuracy, the two-potential approach can be modified to a form resembling the R-matrix theory, yet without any uncertainties of the latter related to the choice of the matching radius.Comment: 7 two-column pages, 3 figures, extra-explanation added, Phys. Rev. A, in pres

The 4-particle hydrogen-antihydrogen system revisited: twofold Hamiltonian symmetry and natural atom antihydrogen

Modern ab initio treatments of H-Hbar systems are inconsistent with the logic behind algebraic Hamiltonians H(+-)=H(0)+/-deltaH for charge-symmetrical and charge-asymmetrical 4 unit charge systems like H(2) and HHbar. Since these 2 Hamiltonians are mutually exclusive, only the attractive one can apply for stable natural molecular H(2). A wrong choice leads to problems with antiatom Hbar. In line with earlier results on band and line spectra, we now prove that HL chose the wrong Hamiltonian for H(2). Their theory explains the stability of attractive system H(2) with a repulsive Hamiltonian instead of with the attractive one, representative for charge-asymmetrical system HHbar. A new second order symmetry effect is detected. Repulsive HL Hamiltonian H(+) applies at long range but at the critical distance, attractive charge-inverted Hamiltonian H(-)takes over and leads to bond H(2) but in reality, HHbar, for which we give an analytical proof. Another wrong asymptote choice in the past also applies for atomic antihydrogen Hbar, which has hidden the Mexican hat potential for natural hydrogen. This generic solution removes most problems, physicists and chemists experience with atomic Hbar and molecular HHbar, including the problem with antimatter in the Universe.Comment: at the instituional UGent archive, 37 pag, 10 fig, tabb, version as submitted, abstract shortene

Nonperturbative Coherent Population Trapping: An Analytic Model

Coherent population trapping is shown to occur in a driven symmetric double-well potential in the strong-field regime. The system parameters have been chosen to reproduce the $0^{-}\leftrightarrow 3^{+}$ transition of the inversion mode of the ammonia molecule. For a molecule initially prepared in its lower doublet we find that, under certain circumstances, the $3^{+}$ level remains unpopulated, and this occurs in spite of the fact that the laser field is resonant with the $0^{-}\leftrightarrow 3^{+}$ transition and intense enough so as to strongly mix the $0^{+}$ and $0^{-}$ ground states. This counterintuitive result constitutes a coherent population trapping phenomenon of nonperturbative origin which cannot be accounted for with the usual models. We propose an analytic nonperturbative model which accounts correctly for the observed phenomenon.Comment: 5 pages, 2 figure

CPT\cal CPT-invariant two-fermion Dirac equation with extended hyperfine operator

For the S-states of muonium and positronium, the hyperfine shifts to the order $\alpha^6$ of a recently derived two-fermion equation with explicit $\cal CPT$-invariance are checked against the results of a nonrelativistic reduction, and the leading $\alpha^8$ shifts are calculated. An additional hyperfine operator is discovered which can milden the singularity for $r\to 0$ of the Dirac hyperfine operator, such that the resulting extended operator can be used nonperturbatively. The binding correction to magnetic moments is mentioned

Majorana: from atomic and molecular, to nuclear physics

In the centennial of Ettore Majorana's birth (1906-1938?), we re-examine some aspects of his fundamental scientific production in atomic and molecular physics, including a not well known short communication. There, Majorana critically discusses Fermi's solution of the celebrated Thomas-Fermi equation for electron screening in atoms and positive ions. We argue that some of Majorana's seminal contributions in molecular physics already prelude to the idea of exchange interactions (or Heisenberg-Majorana forces) in his later workson theoretical nuclear physics. In all his papers, he tended to emphasize the symmetries at the basis of a physical problem, as well as the limitations, rather than the advantages, of the approximations of the method employed.Comment: to appear in Found. Phy

Vibrational dynamics and band structure of methyl-terminated Ge(111)

A combined synthesis, experiment, and theory approach, using elastic and inelastic helium atom scattering along with ab initio density functional perturbation theory, has been used to investigate the vibrational dynamics and band structure of a recently synthesized organic-functionalized semiconductor interface. Specifically, the thermal properties and lattice dynamics of the underlying Ge(111) semiconductor crystal in the presence of a commensurate (1 × 1) methyl adlayer were defined for atomically flat methylated Ge(111) surfaces. The mean-square atomic displacements were evaluated by analysis of the thermal attenuation of the elastic He diffraction intensities using the Debye-Waller model, revealing an interface with hybrid characteristics. The methyl adlayer vibrational modes are coupled with the Ge(111) substrate, resulting in significantly softer in-plane motion relative to rigid motion in the surface normal. Inelastic helium time-of-flight measurements revealed the excitations of the Rayleigh wave across the surface Brillouin zone, and such measurements were in agreement with the dispersion curves that were produced using density functional perturbation theory. The dispersion relations for H-Ge(111) indicated that a deviation in energy and lineshape for the Rayleigh wave was present along the nearest-neighbor direction. The effects of mass loading, as determined by calculations for CD_3-Ge(111), as well as by force constants, were less significant than the hybridization between the Rayleigh wave and methyl adlayer librations. The presence of mutually similar hybridization effects for CH_3-Ge(111) and CH_3-Si(111) surfaces extends the understanding of the relationship between the vibrational dynamics and the band structure of various semiconductor surfaces that have been functionalized with organic overlayers

Hybridization of Surface Waves with Organic Adlayer Librations: A Helium Atom Scattering and Density Functional Perturbation Theory Study of Methyl-Si(111)

The interplay of the librations of a covalently bound organic adlayer with the lattice waves of an underlying semiconductor surface was characterized using helium atom scattering in conjunction with analysis by density functional perturbation teory. The Rayleigh wave dispersion relation of CH_(3)- and CD_(3)-terminated Si(111) surfaces was probed across the entire surface Brillouin zone by the use of inelastic helium atom time-of-flight experiments. The experimentally determined Rayleigh wave dispersion relations were in agreement with those predicted by density functional perturbation theory. The Rayleigh wave for the CH_(3)- and CD_(3)-terminated Si(111) surfaces exhibited a nonsinusoidal line shape, which can be attributed to the hybridization of overlayer librations with the vibrations of the underlying substrate. This combined synthetic, experimental, and theoretical effort clearly demonstrates the impact of hybridization between librations of the overlayer and the substrate lattice waves in determining the overall vibrational band structure of this complex interface