On the thermal decomposition of COS

The thermal dissociation of COS was investigated in shock waves with argon as carrier gas. The concentration was varied between 0.05 and 0.5% COS in argon, the total density from 2.5 × 10^?5 mole/cm³ to 2.5 × 10^?3 mole/cm³. Temperatures between 1500°K and 3100°K were applied. For the reaction the rate constant was found to be in the low pressure range of the unimolecular reaction and in the high pressure range.     

Charge referencing issues in XPS of insulators as evidenced in the case of Al‐Si‐N thin films

Accurate charge referencing in XPS of insulating specimens is a delicate issue. This difficulty is illustrated in the case of Al‐Si‐N composite thin films deposited by reactive magnetron sputtering with variable composition from pure aluminum nitride to pure silicon nitride. The samples were mounted with Au‐coated metallic clamps. Argon sputter cleaning was required to remove a surface native oxide before analysis. For charge referencing implanted argon atoms from the sputter gas and a small amount of gold re‐deposited from the metallic clamps onto the specimen surface during sputter cleaning were evaluated. For the argon atoms, a surprisingly large chemical shift (～1 eV) and a significant peak broadening (0.6 eV) of the Ar 2p_3/2 photoelectron line were found with varying the Si content of the films. This could be related to chemical and structural changes of the Al‐Si‐N films. Hence implanted argon could not be used for charge referencing of Al‐Si‐N samples. In contrast to the implanted argon, the Au 4f_7/2 line width of the gold re‐deposited onto the sample surface did not depend on the Si content of Al‐Si‐N films. A constant energy shift (～1.2 eV) of the Au 4f_7/2 line as compared with bulk gold was, however, found, which was related to the size of gold particles formed on the insulating films. Therefore gold could be reliably used to study chemical shifts of sample‐relevant species in Al‐Si‐N films, but the absolute binding energies of Al 2p, Si 2p and N 1s photoelectrons could not be determined. Copyright © 2011 John Wiley & Sons, Ltd.     

Laser spectroscopy of nuclear reaction products: recent results and future prospects

Laser spectroscopic observations of nuclear reaction products produced with intensities of less than 10⁴ atoms/second are now possible with several different methods. We describe the recoil into gas method which has recently been successful. This method is not Dopplerfree, but can give reasonable spectra if the resolution requirements of the spectra are not too high. It has the great advantage that it very efficiently uses the atoms, and spectra have been observed with primary production rates of less than 10³ atoms/sec. Our recent work has concentrated on developing the recoil into gas method for the refractory element Hf. In order that the atoms could be cycled to produce many fluorescence photons, nitrogen and hydrogen impurity gases were added to the argon buffer gas to quench metastable levels to the ground state. In this way spectra could be obtained with fluxes of 10⁴ atoms/second. Future prospects for trapping radioactive atoms in a magneto-optic trap will be discussed.     

Extrapolation of Laboratory Reaction Kinetic Data for Relief Vent Design in the Case of a Heterogeneous Runaway Reaction

The relief area sizing of safety devices in the case of a postulated thermal runaway condition requires reaction kinetic data, usually measured in dedicated adiabatic calorimeters. In the course of the design, it is then assumed that the same reaction kinetic data prevail on the laboratory and production scale. This assumption seems to be valid in the case of homogeneous reaction systems. In contrast to this the results of experiments with a heterogeneous system have shown that the stirring intensity and the reactor size have a considerable influence on the reaction progress.This revised version was published online in November 2005 with corrections to the Cover Date.     

Subharmonic resonant optical excitation of confined acoustic modes in a free-standing semiconductor membrane at GHz frequencies with a high-repetition-rate femtosecond laser

We propose subharmonic resonant optical excitation with femtosecond lasers as a new method for the characterization of phononic and nanomechanical systems in the gigahertz to terahertz frequency range. This method is applied for the investigation of confined acoustic modes in a free-standing semiconductor membrane. By tuning the repetition rate of a femtosecond laser through a subharmonic of a mechanical resonance we amplify the mechanical amplitude, directly measure the linewidth with megahertz resolution, infer the lifetime of the coherently excited vibrational states, accurately determine the system's quality factor, and determine the amplitude of the mechanical motion with femtometer resolution.     

Beyond metric gravity: Progress on PS-200

The reconciliation of quantum mechanics and gravity on varying distance scales requires changes to General Relativity that may have testable implications. We briefly review the status of tests with matter of the inverse square law and the principle of equivalence, then report on progress on the drift-tube measurement section of PS-200, the experiment to measure the gravitational acceleration of antiprotons.     

Über die Menge der Zahlen,die als Minima quadratischer formen auftreten

It is proved that the Markoff spectrum and the Perron spectrum both contain the interval with endpoints 0 and $\text{1}\text{(21)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$. Both sets have a gap near $\text{1}\text{4,5217}$.     

Isotope shift measurements and charge radii of152–158Yb

Isotope shifts have been measured for the neutron deficient even Yb isotopes up to the neutron shell closure at N=82. The isotope shifts were measured using the 556-nm atomic resonance transition from the¹ S ₀ ground state to the³ P ₁ level. The heavier isotopes of Yb have been investigated by Buchinger et al./1/. The change in (r ²) observed for Yb isotopes with N=82–90 has considerably different behavior than for the lighter rare earths.