Improvement of average laser power and beam divergence of a high pulse repetition frequency excimer laser

Received: 3 January 1997/Revised version: 13 May 1997     

A possible mechanism for benzene formation during the pyrolysis of poly(vinyl chloride)

We studied the evolution of hydrogen chloride and benzene from two PVC samples differing only in molecular weight, during a slow pyrolysis experiment. It appears that the evolution rates and total amount of benzene decrease rapidly when molecular weight increases. Twenty to 30 benzene molecules are formed per initial chain-end. The proposed radical mechanism involves a cyclohexadienyl radical as intermediate and initiation from terminal 1-chloro-vinyl units.     

Synthesis of nanostructured metal-organic films: surface X-ray radiolysis of silver ions using a langmuir monolayer as a template

An application of the radiolysis method using an X-ray synchrotron beam is developed as a novel approach to the synthesis of metal-organic films with controlled shapes and thickness. We demonstrate that a Langmuir monolayer deposited onto a silver ion containing subphase, irradiated by an incident beam impinging below the critical angle for total reflection, induces the synthesis of a stable nanostructured silver-organic ultrathin film at the air-water interface. The X-ray scattering is also used to monitor in situ the structure of the silver layer during the synthesis process. The layer is observed by atomic force microscopy after its transfer onto a silicon substrate. One observes a film thickness of 4.6 nm, in good agreement with the X-ray penetration depth, about 4.5 nm. The silver structure is oriented by the initial organic film phase. This experiment demonstrates the considerable potential of this approach to produce various controlled metal-organic films with a surfactant self-assembly as a template.     

Lattice systems with a continuous symmetry

We investigate a continuous Ising system on a lattice, equivalently an anharmonic crystal, with interactions: $$\sum\limits_{\left\langle {x,y} \right\rangle } {\left( {\phi _x - \phi _y } \right)} ^2 + \lambda \left( {\phi _x - \phi _y } \right)^4 , \phi _x \in \mathbb{R}, x \in \mathbb{Z}^d .$$ We prove that the perturbation expansion for the free energy and for the correlation functions is asymptotic about λ=0, despite the fact that the reference system (λ=0) does not cluster exponentially. The results can be extended to more general systems of this type, e.g. an even polynomial semibounded from below instead of a quartic interaction. By a suitable scaling, λ corresponds to the temperature.     

Infrared bounds and the peierls argument in two dimensions

We propose a definition of contours for spin systems which leads to improved estimates on the region of parameters where several phases coexist. We discuss as examples anisotropic rotators and a ⁴ lattice field theory. Our contours are estimated using infrared bounds and they are related to those of Euclidean Field Theory.Part of this work was done while Jean Bricmont was at the Mathematics Department of Princeton University and Jean-Raymond Fontaine was at the Mathematics Department of Rutgers University. This work was supported by NSF Grant No. MCS 78-01885 at Princeton University and by NSF Grant No. PHY 78-15920 at Rutgers University