Close coupling results for inelastic collisions of NH3 and Ar. A stringent test of a spectroscopic potential

We have calculated state-to-state total cross sections for rotational excitation and inversion of NH3 by collisions with Ar using the close coupling method. The Ar-NH3 interaction potential has been obtained from a fit to the spectrum of this van der Waals molecule. The calculated cross sections agree to within about 30% with the measured values; the estimated error in the latter is 10% to 20%.     

Longitudinal-transverse interference structure function in the reaction2H(e,e′ p)

The longitudinal-transverse interference structure functionf ₀₁ has been measured in deuterium electrodisintegration experiments at various values of the four-momentum transferQ ². Data taken at different laboratories and at roughly the same value ofQ ² are shown to be consistent. When compared to non-relativistic impulse-approximation calculations mostf ₀₁ data show an enhancement. A relativistic treatment of the reaction²H(e, e p) removes the discrepancy. More definite evidence for relativistic effects in deuterium electrodisintegration can be obtained at higher values of the recoil momentum. The experimental implications for such²H(e, e p) experiments are discussed as well.Dedicated to Prof. Werner Sandhas on the occasion of his 60th birthday     

Photorefractive properties of ruthenium-doped potassium niobate

Photoconductivities and photovoltaic currents of ruthenium-doped KNbO₃ are orders of magnitude larger than that of undoped and ion-doped crystals. KNbO₃:Ru is very sensitive for holographic recording with red light and the photovoltaic current increases sublinearly with light intensity.     

A matrix integral solution to [P,Q]=P and matrix laplace transforms

In this paper we solve the following problems: (i) find two differential operatorsP andQ satisfying [P, Q]=P, whereP flows according to the KP hierarchy P/t _n =[(P ^n/p )₊,P], withp:=ordP2; (ii) find a matrix a integral representation for the associated -function. First we construct an infinite dimensional spaceW= span{ ₀(z, ₁(z,...)} of functions ofz invariant under the action of two operators, multiplication byz ^p andA _c :=z/z–z+c. This requirement is satisfied, for arbitraryp, if ₀ is a certain function generalizing the classical Hänkel function (forp=2); our representation of the generalized Hänkel function as adouble Laplace transform of a simple function, which was unknown even for thep=2 case, enables us to represent the -function associated with the KP time evolution of the spaceW as a double matrix Laplace transform in two different ways. One representation involves an integration over the space of matrices whose spectrum belongs to a wedge-shaped contour ^-+ ^- defined by ^± = ₊e^±i/p. The new integrals above relate to matrix Laplace transforms, in contrast with matrix Fourier transforms, which generalize the Kontsevich integrals and solve the operator equation [P, Q]=1.The support of a National Science Foundation grant #DMS-95-4-51179 is gratefully acknowledged.The hospitality of the Volterra Center at Brandeis University is gratefully acknowledged.The hospitality of the University of Louvain and Brandeis University is gratefully acknowledged.The support of a National Science Foundation grant #DMS-95-4-51179, a Nato, an FNRS and a Francqui Foundation grant is gratefully acknowledged.