2 edition of Formation and destruction of fast metastable helium beams. found in the catalog.
Formation and destruction of fast metastable helium beams.
Kenneth Francis Dunn
Written in English
Thesis (Ph. D.)--The Queen"s University of Belfast, 1970.
|The Physical Object|
Abstract. It is possible to cool metastable (2 3 S 1) Helium by interaction with a laser at μm, since the transition 2 3 S 1 – 2 3 P 2 is a closed transition. Helium is a very attractive system for many reasons: for example it is a simple atom, and progress in its spectroscopic measurements may lead to improved accuracy in fundamental constants (α). The formation of metastable helium in large amounts on exoplanets was theorized a long time ago but up until now, it had never actually been detected. This .
Fast Beam Experiment This charge exhange method is used in the fast beam experiment. A RF ion source produces a keV He + beam. The ion beam is passed through a cesium vapor target to produce the metastable helium atoms. The remaining ions are deflected out of the way with a set of deflection plates in the next chamber, leaving only the. An illustration of an open book. Books. An illustration of two cells of a film strip. Video. An illustration of an audio speaker. Audio. An illustration of a " floppy disk. Full text of "Sputtering and ionization by helium and argon in the microsecond pulsed glow discharge using time-of-flight mass spectrometry".
Electron and Metastable Production Profiles In Helium Fast Ionization Waves B. R. Weatherford1, E. V. Barnat1, Z. Xiong2, and M. J. Kushner2 1Sandia National Laboratories, Albuquerque, NM USA; 2University of Michigan, Ann Arbor, MI, USA Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed.  Models of metastable helium, He(2 3 S), production in the upper thermosphere and lower exosphere show that creation by recombination of He + may be nonnegligible relative to the photoelectron impact on He(1 1 S) source. Owing to large ground state He abundance in the winter and to photoelectrons from an illuminated conjugate thermosphere, the strongest nm intensities (arising from He.
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Formation and destruction of fast metastable helium beams. Author: Dunn, K. ISNI: Awarding Body: Queen's University Belfast Current Institution: Queen's University Belfast Date of Award: Availability of Full Text: Full text unavailable from EThOS.
collisions during passage of fast helium beams through hydrogen To cite this article: H B Gilbody et al J. Phys. B: At. Mol. Phys. 2 View the article online for updates and enhancements. Related content Formation and destruction of fast metastable helium atoms in charge-changing collisions H B Gilbody, R Browning, G Levy et al.-Cited by: Surface Science 92() North-Holland Publishing Company CONTAMINATION OF A BEAM OF METASTABLE HELIUM ATOMS BY FAST NEUTRAL ATOMS Characteristics of the secondary emission of these atoms at low energy ( eV) in interaction with the surface of a solid Centre d'Etudes Nucleaires de Sac-lay, Service (ie Cited by: Download Citation | Destruction of fast metastable hydrogen atoms passing through atomic helium | The first Born approximation is used to calculate cross sections for excitation or de-excitation.
quence, the most rapid decay process from the metastable to the ground state is via a magnetic-dipole-allowed, single-photon transition at nm in the XUV region.
FIG. 1 (color online). Energy level diagram for helium. Excited-state decays to the ground state are indicated, along with laser transitions from the metastable 23S 1 by: Abstract. Total cross sections in the energy range keV for destruction of metastable helium atoms (i.e., electron loss and deexcitation) penetrating H 2, He, N 2, Ne, or Ar gas targets have been measured by the beam-attenuation fast, metastable helium atoms were formed by electron detachment from He-ions in either a strong electric field or under single-collision.
Exited atoms may relax to the ground state by radiative decay, a process which is usually very fast (of order nanoseconds). However, quantum-mechanical selection rules can prevent such rapid decay, in which case these "metastable" states can have lifetimes of order seconds or longer. In this Letter, we determine experimentally the lifetime of the longest-lived neutral atomic state-the first.
The role of fast metastable helium atoms in the formation of He-ions by charge-changing collisions during the passage of kev helium beams through hydrogen has been investigated quantitatively.
It is shown that He-ions are formed by collisions involving one-electron capture by fast metastable helium atoms while all other possible production mechanisms are found. The laser beam passed through the second cell, 9-cm long and 5 cm in diameter.
The helium pressure was equal to p He = 6 15 Torr. Molecular gas pressures were changed in a range of 5 mTorr when the rate quenching constants of MS He (2 1 S 0) was helium pressure was chosen such that the collisional broadening of the line on the transition (2 1 P 1 0 − 2 1. Formation of High Helium Gases: A Guide for Explorationists* Alton A.
Brown 1 Search and Discovery Article # () Posted Octo *Adapted from poster presentation at AAPG Convention, New Orleans, Louisiana, April1Consultant, Richardson, TX ([email protected]).
Abstract In this note we report on simple estimates of the properties of metastable solid helium that is at a pressure below the normal melting pressure.
We calculate the nucleation rate for formation of the liquid phase and estimate the “spinodal” pressure at which the solid becomes macroscopically unstable. The role of fast metastable helium atoms in the formation of He- ions by charge-changing collisions during the passage of kev helium beams through hydrogen has been investigated quantitatively.
Ratios R of the cross sections for associative to the sum of associative and Penning ionization have been measured using molecular beams of thermal energy (°K) metastable atoms, A *, incident on a gas B confined in a collision chamber at low pressures, where A * is either 2 1,3 S helium or 3 P 2,0 neon and B is argon or krypton.
By determining R as a function of the collision chamber. 0 Reviews. A consistent, up-to-date description of the extremely manifold and varied experimental techniques which nowadays enable work with neutral particles.
Th book lays the physical foundations. This dissertation describes experiments to develop and realize an atomic decelerator (or "slower") for metastable helium using the optical bichromatic force (BCF).
The research comprises two subtopics—using the bichromatic force at very large detunings, and developing a chirped BCF slower.
There is experimental evidence that as bichromatic detunings approach times the natural. We studied the dynamics of thermoluminescence during destruction of porous structures formed by nanoclusters of nitrogen molecules containing high concentrations of stabilized nitrogen atoms.
The porous structures were formed in bulk superfluid helium by injection of the products of discharges in nitrogen–helium gas mixtures through the liquid helium surface. A calculation of the cross section for the reaction He′+He′=He+He + +e (destruction of the metastable 2 3 S state by ionization) has been performed by means of the perturbed stationary state method.
The cross section obtained is of the order of magnitude 10 —18 cm 2 at room temperature and increases slowly with decreasing kinetic energy of the colliding particles. Understanding the migration of either positive or negative charges in liquid helium is essential to comprehend charge-induced processes in molecular systems embedded in helium droplets.
Here, we report the resonant formation of excited metastable atomic and molecular helium anions in superfluid helium droplets upon electron impact.
Chemi-ionization reactions involving metastable helium atoms at high energy P. Pradel and J. Laucagne Service de Physique des Atomes et des Surfaces, Centre d Etudes Nucléaires de Saclay, Gif-sur-Yvette Cedex, France (Reçu le 2 mairevise le 7 juillet, accepte le 28 juillet ) Résumé.
Nous avons utilisé un faisceau rapide d atomes d hélium métastable en. Abstract A compact, high-intensity helium metastable source is described for use in surface spectroscopy experiments. This source, based on electron bombardment of a helium beam, produces a helium metastable flux of 4 x atoms s-1 sr-l, with a stability of 2%, and an effective ultraviolet photon content of less than 1 %.
ection of metastable helium atoms using resonant nm laser light is described. By scattering photons, the metastable helium atoms gain the momentum of the absorbed photons in the direction of illumination. This results in a de ection of the atom beam.
The main goal of this research is to determine the relation between the de ection of the atom.texts All Books All Texts latest This Just In Smithsonian Libraries FEDLINK (US) Genealogy Lincoln Collection. National Emergency Library. Top American Libraries Canadian Libraries Universal Library Community Texts Project Gutenberg Biodiversity Heritage Library Children's Library.
Open Library.of which only two i.e. helium-3 (with 1 neutron) and helium-4 (with 2 neutrons) are -3 atoms are fermions and the helium-4 atoms are bosons.
Due to low molar mass, helium has greater thermal conductivity, specific heat and sound speed than any other gas except hydrogen. Helium has high diffusivity through solids. Helium is the.