Free states and automorphisms of the Clifford algebra

We study automorphisms of the Clifford algebra which map the set of quasi-free states onto itself. We show that they are quasi-free if the one-particle space is infinite dimensional, and give counter examples in finite dimensions.     

An optically-pumped proton maser

The nuclear polarization of protons in a Yb-doped yttrium ethyl sulfate crystal is found to invert by simply illuminating the crystal with near-infrared radiation. A nuclear enhancement of −15 is observed at 1.4 K and H = 15 kOe. This novel dynamic polarization effect is apparently caused by optical pumping of the paramagnetic Yb³⁺ spin. When the crystal is placed in a high-Q NMR circuit at 60 MHz, maser oscillations are induced by the incident light.     

Glass column connector for a gas chromatograph

A cheap glass—metal connector is described for use with glass columns, to avoid the problems of O-rings or special ferrules. The device is valuable in gas chromatography of amino acid derivatives.     

On the unimodality of spherically symmetric stable distribution functions

Several theorems are obtained concerning the unimodality of spherically symmetric distribution functions. These theorems are used to show that a class of spherically symmetric infinitely divisible distribution functions that contains the class of spherically symmetric stable distribution functions is unimodal.     

On the finite series expansion of multivariate characteristic functions

Three theorems are obtained that relate the asymptotic behavior of a distribution function with the behavior of its characteristic function at the origin. These theorems generalize one dimensional results that have been obtained by the author and by others.     

Atomic oxygen reactions with semifluorinated and n-alkanethiolate self-assembled monolayers

The interaction of atomic oxygen (O(3P)) with semifluorinated self-assembled monolayers (CF-SAMs), two different n-alkanethiolate self-assembled monolayers, and a carbonaceous overlayer derived from an x-ray modified n-alkanethiolate SAM have been studied using in situ x-ray photoelectron spectroscopy. For short atomic oxygen exposures, CF-SAMs remain intact, an effect ascribed to the inertness of C-F and C-C bonds toward atomic oxygen and the well-ordered structure of the CF-SAMs. Following this initial induction period, atomic oxygen permeates through the CF3(CF2)7 overlayer and initiates reactions at the film/substrate interface, evidenced by the formation of sulfonate (RSO3) species and Au2O3. These reactions lead to the desorption of intact adsorbate chains, evidenced by the loss of carbon and fluorine from the film while the C(1s) spectral envelope and the C(1s)/F(1s) ratio remain virtually constant. In contrast, the reactivity of atomic oxygen with alkanethiolate SAMs is initiated at the vacuum/film interface, producing oxygen-containing carbon functional groups. Subsequent reactions of these new species with atomic oxygen lead to erosion of the hydrocarbon film. Experiments on the different hydrocarbon-based films reveal that the atomic oxygen-induced kinetics are influenced by the thickness as well as the structural and chemical characteristics of the hydrocarbon overlayer. Results from this investigation are also discussed in the context of material erosion by AO in low Earth orbit.