Laser-stimulated desorption of potassium atoms

Desorption of K atoms by laser-excitation of surface plasmons in small K particles is reported. The desorption rate has been measured for different laser wavelengths and particle sizes. Time-of-flight measurements reveal a kinetic energy of the desorbed atoms of E_kin=0.13(3) eV. From the experimental data it is concluded that the desorption mechanism is non-thermal in nature. Comparison of the results reported here with our earlier work on Na desorption is made.     

Streuwirkungsquerschnitte12C(p,p)12C undl2C(d,d)12C im EnergiebereichE p=350...550 keV,bzw.E d=600...1100 keV

Scattering Cross Sections¹²C(p, p)¹²C and^l2C(d, d)¹²C in the Energy Range E_p=350...550 keV resp. E_d=600...1,100 keV For an application in a work in nuclear solid state physics (elastic recoil detection with fast¹²C-ions) the scattering cross sections were measured. When adapting excitation functions with a Breit-Wigner formalism it was found that a satisfactory adaptation needed the reduction of one hard-sphere phase by the factor 0.4, and smaller, in order to maintain a reasonable value of the interaction radius.     

Exact penalty results for mathematical programs with vanishing constraints

A mathematical program with vanishing constraints (MPVC) is a constrained optimization problem arising in certain engineering applications. The feasible set has a complicated structure so that the most familiar constraint qualifications are usually violated. This, in turn, implies that standard penalty functions are typically non-exact for MPVCs. We therefore develop a new MPVC-tailored penalty function which is shown to be exact under reasonable assumptions. This new penalty function can then be used to derive (or recover) suitable optimality conditions for MPVCs.     

Lineare funktionale Differentialgleichungen

Ohne Zusammenfassung     

First-and second-order optimality conditions for mathematical programs with vanishing constraints

We consider a special class of optimization problems that we call Mathematical Programs with Vanishing Constraints, MPVC for short, which serves as a unified framework for several applications in structural and topology optimization. Since an MPVC most often violates stronger standard constraint qualification, first-order necessary optimality conditions, weaker than the standard KKT-conditions, were recently investigated in depth. This paper enlarges the set of optimality criteria by stating first-order sufficient and second-order necessary and sufficient optimality conditions for MPVCs. Dedicated to Jiří V. Outrata on the occasion of his 60th birthday. This research was partially supported by the DFG (Deutsche Forschungsgemeinschaft) under grant KA1296/15-1.     

Transport coefficients of liquid N2 computed by molecular dynamics

Summary With three potential functions including quadrupole interaction, we computed the shear and the bulk viscosity coefficients as well as the thermal conductivity by molecular dynamics for a number of states of liquid nitrogen. The results indicated that the transport coefficients are determinable with a statistical error of about 10 per cent, even for the angledependent molecular potentials in the rigid-rotor approximation. An exception represents the bulk viscosity, for which systems of large particle numbers are necessary to reach the few perent accuracy for states near the triple point. The quadrupole interaction affects weakly the time correlation functions and thus the transport coefficients. In several cases, it improves, however, the agreement with experimental data. Paper presented at the workshop ?Highlights on Simple Liquids?, held in Turin at ISI on 1–3 May, 1989.     

Time-dependent properties of the fluid mixture Ne/Kr in the region of the critical mixing point at about 2000 bar

In continuation of our previous molecular dynamics calculations [1], the dynamic structure of the fluid mixture Ne/Kr is investigated in the region of its upper critical mixing point at high pressures. The time-dependent pair-distribution functions have been found to change anomalously near the critical point, relative to the range far above. These changes can be explained by a large increase in the characteristic time of the system close to its critical point, in agreement with experimental findings on other liquids and binary mixtures and theoretical predictions. Our calculations yield a correlation time which is about four times larger than for the non-critical system, in accord with light scattering experiments on similar systems. It is therefore confirmed again that MDC, using effective Lennard-Jones (12–6) potentials, is able to simulate satisfactorily many features of the real Ne/Kr system, including its gas-gas equilibrium of the second kind.