Isotope effects in the metastable decay of Ne2 +

Neon dimer ions undergo spontaneous dissociation (metastable decay) several microseconds after formation by electron impact ionization of neon clusters. In this contribution we compare the kinetic energy release distribution (KERD) of the previously reported isotopomer ²⁰Ne₂ ⁺ with that of ²²Ne₂ ⁺. The heavy isotopomer shows the same two components in the KERD as the lighter ones. However, the high-energy component that is due to electronic pre-dissociation is reduced in intensity. The decrease is attributed to a reduced predissociation rate from the II(1/2u) state into I(3/2u).     

HORMANDER MULTIPLIER THEOREM ON SU(2)

ＨＲＡＮＤＥＲＭＵＬＴＩＰＬＩＥＲＴＨＥＯＲＥＭＯＮＳＵ（２）￥ＦＡＮＤＡＳＨＡＮ；ＸＵＺＥＮＧＦＵ（ＤｅｐａｒｔｍｅｎｔｏｆＭａｔｈｅｍａｔｉｃｓ，ＡｕｈｕｉＵｎｉｖｅｒｓｉｔｙｔＨｅｆｅｉ２３００３９，Ｃｈｉｎａ．）Ａｂｓｔｒａｃｔ：Ａｂｏｕｎｄ...     

New parameterization of the trinucleon wave function and its application to the π <Superscript>3</Superscript>He scattering length

We present a new parameterization of the trinucleon wave function. As a novel feature a separable parameterization for the complete wave function is given. In this way any calculation that considers two-body currents only is largely simplified. To demonstrate this we calculate the π³He scattering length in chiral-perturbation theory. We find reasonable agreement with experimental values inferred from data on level shifts in pionic ³He bound states. The relevance of the π-triton system for an alternative determination of the πN scattering lengths is discussed. Received: 12 August 2002 / Accepted: 25 November 2002 / Published online: 25 February 2003 RID="a" ID="a"e-mail: c.hanhart@fz.juelich.de Communicated by V. Vento     

Perspectives of laser processing and chemistry

Laser-induced material processing is reviewed with special emphasis on recent achievements mainly obtained by the Linz group. Among those are investigations using optical fiber tips for nanoscale photophysical etching, laser-induced surface patterning using self-assembled microspheres, the pulsed-laser deposition of thin films of high-temperature superconductors and the modification and cleaning of surfaces. Received: 7 February 2003 / Accepted: 6 March 2003 / Published online: 28 May 2003 RID="*" ID="*"Corresponding author. Fax: +43-732/2468-9242, E-mail: dieter.baeuerle@jku.at     

Controlling wettability by light: illuminating the molecular mechanism

The functionalisation of a surface with an organic monolayer containing photoactive moieties such as the azobenzene chromophore opens an elegant route for controlling its wettability by light. In this paper we investigate the microscopic origin of the macroscopic change in wettability upon photo-induced cis-trans isomerization of a copolymeric diphenyl-diazene Langmuir-Blodgett monolayer. Polarised UV-Vis and FTIR spectroscopy have been used to monitor the orientational order of various functional groups, Atomic Force Microscopy and Imaging Ellipsometry is employed for the quantification of the surface roughness and morphology, contact angle and surface potential measurements are carried out for a characterisation of the polar ordering. The data analysis is further supported by semi-empirical and ab-initio calculations of the molecular dipole moments and the normal IR-modes of the fluorinated chromophore. The combination of all these techniques provides a detailed molecular picture. The data suggest that changes in the projection of the dipole moment onto the surface normal caused by isomerization of the azobenzene are responsible for the observed changes in the surface energy. This knowledge allowed us to predict guidelines for the synthesis of molecules in order to maximize the wetting contrast upon photo-irradiation. Received 5 September 2002 Published online: 16 April 2003 RID="a" ID="a"e-mail: hubert.motschmann@mpikg-golm.mpg.de     

Photoacoustic signal enhancement at visible and X-ray wavelengths

Good agreement between theory and experiment is found for photoacoustic (PA) signal enhancement by volatile liquids adsorbed on solid samples in a microphonic cell illuminated with visible light. When the same solid samples are illuminated with synchrotron X-radiation significantly smaller PA signal enhancements are observed than are predicted by theory because of radiolysis of the liquid vapors. The introduction of the volatile liquids is nevertheless valuable for the X-ray photoacoustic measurements because it raises the signal above the threshold for detectability.     

Acousto-optic amplitude modulation and demodulation of electromagnetic wave in magnetised diffusive semiconductors

Using hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave in a transversely magnetised acousto-optic semiconducting plasma. The inclusion of carriers diffusion adds new dimension in the analysis presented here. Analysis are made under different wave number regions over a wide range of cyclotron frequency. It has been seen that diffusion of charge carriers modifies amplitude modulation and demodulation processes effectively. Numerical estimations are made for n-InSb crystal irradiated by pump wave of frequency 1.6 T s^-1. Complete absorption of the waves takes place in all the possible wave lengths regimes when the cyclotron frequency becomes exactly equal to (v ² + )^1/2. Received 28 February 2002 Published online 19 July 2002     

A theory for the enhancement of the photoacoustic signals by volatile liquids

It has been shown experimentally that photoacoustic signals can be enhanced by introduction of a volatile liquid into the cell. Korpiun developed a theory which predicted the enhancement to be proportional to the mole fraction of the volatile component (y ₀) in the gas phase. His theory is, however, based on a species conservation equation valid for dilute solutions only. We present a rigorous theory for predicting the enhancement of potoacoustic signal. Our theory shows the enhancement to be proportional toy ₀/(1–y ₀) which compares well with observations of Ganguly and Somasundaram.     

High-frequency response and wavelength dispersion of the linear electro-optic effect in PZN-PT (88/12) single crystal

We have characterized the wavelength dispersion of the high- and low-frequency values of the linear electro-optic coefficient r _c = r ₃₃–(n _o/n _e)³ r ₁₃ of poled 0.88 Pb(Zn_1/3Nb_2/3)O₃–0.12 PbTiO₃ single crystal. The measurements have been investigated as a function of the laser wavelength from 0.465 to 1.32 m. Clamped r ^S and unclamped r ^T values of the electro-optic coefficient as well as the acoustic contribution r ^a have been established. We obtained a ratio of r ^S/r ^T = 30%, which is independent of the wavelength of the light beam. The value of r ^S _c at the wavelength of 633 nm was found to be equal to 50±5 pm/V, which is a rather high value.This revised version was published online in March 2005. In the previous version, the published online date was missing