Theory of collision-induced ionization of adsorbed species on solid surfaces in the presence of laser radiation

A formalism is proposed for treating the problem of ionization of adsorbed species on solid surfaces. The ionizing agents are taken to be impact atoms and laser radiation with frequency low compared to the inverse of characteristic collision times. The physical constraints of short collision times and low laser frequency then allow one to treat the adatom-surface-plus-field system under the quasi-static approximation (QSA) and the impact-atom-adatom-surface collision dynamics under the impulse approximation (IMA). The latter leads to a time-dependent ionization cross-section which is factorizable into the square of an electron-atom scattering matrix element and a spectral function describing the energy-momentum distribution of electrons in the adatom-surface-plus-field system. The formalism focuses on the spectral function which is shown to be derivable from a single-particle Green's function exactly calculable for the present problem.     

The 6− analog-antianalog states of 28Si

A resonance is observed in the ²⁷Al(p, γ)²⁸Si reaction at E_p=2876±2 keV, which corresponds to an excitation energy of 14356±2 keV. The 14.36 MeV level decays to a new level at 11577±2 keV, which is turn decays to the known level at 9701.8±0.5 keV. With previous information on the 9.70 MeV level and the present γ-ray angular distributions, obtained from singles spectra as recorded by a 40 cm³ Ge(Li) detector, the spins of the three levels can be limited to J=5, 6; J=6; and J=5, respectively. Transition strength arguments based on measurements of the strength of the 2876 keV resonance and the lifetime of the 11.58 MeV level indicate that the 14.36 MeV level has J^π=6^?, T=1 and that the 11.58 MeV level has J^π=6^?, T=0.     

Electric field penetration into a hemispherical indentation

In studying the receiving properties of certain aircraft antennas a Dirichlet boundary value problem arises, which consists in determining the penetration of an electric field into a hemispherical indentation in an infinite conducting plane. The problem is solved exactly by performing an inversion transformation on the known potential function for a perfectly conducting right-angled wedge. The electrostatic potential, the surface charge density, and the induced electric dipole moment are obtained in closed form.

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Zusammenfassung Bei der Untersuchung von Flugzeugantennenempfangseigenschaften tritt das Dirichletsche Randwertproblem auf, die Eindringung eines elektrischen Feldes in eine halbkugelförmige Höhlung zu bestimmen, die auf einer vollkommen leitenden, unendlichen Ebene liegt. Dieses Problem wird exakt gelöst, indem man eine Kugelspiegelung auf die bekannte, für einen vollkommen leitenden, rechteckigen Keil geltende Potentialfunktion durchführt. Dabei werden die elektrostatische Potential, die Flächenladungsdichte, sowie das induzierte elektrische Dipolmoment der Höhlung analytisch in geschlossener Form berechnet.

     

Ground state condensate fraction of liquid 4He

An optimal Jastrow correlation function with intermediate- and long-range structure gives a larger condensate fraction at equilibrium density than a simple short-range correlation function. The condensate fraction is also sensitive to the potentials used in the calculation.     

Dye-sensitized photoinitiated cationic polymerization

Several dyes have been discovered which sensitize the photolysis of diaryliodonium salts at visible wavelengths. By using the combination of a dye and a diaryliodonium salt, visible light can be used to photoinitiate cationic polymerization. In this article, the dye-sensitized photopolymerizations of cyclohexene oxide, epichlorohydrin, and 2-chloroethyl vinyl ether are described.     

Barium ferrite (BaFe12O19) thin films prepared by pulsed laser deposition on MgO buffered Si substrates

Barium ferrite (BaFe₁₂O₁₉) thin films have been deposited by pulsed laser deposition (PLD) on Si substrates with MgO underlayers. The films were deposited in oxygen atmosphere by excimer laser (=248 nm, pulse duration=23 ns) in the temperature range 750–900 °C. The experiments showed that the substrate temperature has remarkable effect on the films magnetic and structural properties. The BaFe₁₂O₁₉ films deposited at 900 °C in 200 mTorr oxygen showed some perpendicular orientation, with a perpendicular squareness of 0.5 and an in-plane squareness of 0.3. Such thin BaFe₁₂O₁₉ films have platelet grains with a size of about 300 nm. The perpendicular saturation magnetization and coercivity are 185 emu/cm³ and 1.4 kOe, respectively. PACS 81.15.Fg.; 75.70.Ak; 75.50.Pp; 68.55.j