D. B. Popović

Studies of Dissociative Recombination in CRYRING

This article describes some of the most recent experiments at the ion storage ring CRYRING at the Manne Siegbahn Laboratory, Stockholm University. A comprehensive review of recent work at ion storage rings has recently been published,1 and there are several other reviews of recent date,2,3 as well as the proceedings from the previous dissociative recombination (DR) meeting at Nasslingen in Sweden.4 Finally, a brief review of three-body breakup dynamics has recently been published.5

Electron-impact dissociation of CH{sup +} ions: Measurement of C{sup +} fragment ions

Absolute cross sections for electron-impact dissociation of CH{sup +} producing C{sup +} fragment ions were measured in the 3-100 eV range using a crossed electron-ion beams technique with total uncertainties of about 10% near the cross-section peak. Although the measured energy dependence agrees well with two sets of storage ring measurements, the magnitude of the present results lies about 15-25 % below the other results at the cross-section peak near 40 eV. Below 10 eV, the present data tend to exceed the storage ring data, consistent with the presence of excited states in the CH{sup +} ion beam. For energies above 29 eV, the cross sections should also include contributions from dissociative ionization, though no clear onset of this channel is evident in any of the three sets of measured data.

Positive-operator-valued measures in the Hamiltonian formulation of quantum mechanics

In the Hilbert space formulation of quantum mechanics, ideal measurements of physical variables are discussed using the spectral theory of Hermitian operators and the corresponding projector-valued measures (PVMs). However, more general types of measurements require the treatment in terms of positive-operator-valued measures (POVMs). In the Hamiltonian formulation of quantum mechanics, canonical coordinates are related to PVM. In this paper the results of an analysis of various aspects of applications of POVMs in the Hamiltonian formulation are reported. Several properties of state parameters and quantum observables given by POVMs or represented in an overcomplete basis, including the general Hamiltonian treatment of the Neumark extension, are presented. An analysis of the phase operator, given by the corresponding POVMs, in the Hilbert space and the Hamiltonian frameworks is also given.

Cloning in nonlinear Hamiltonian quantum and hybrid mechanics

Possibility of state cloning is analyzed in two types of generalizations of quantum mechanics with nonlinear evolution. It is first shown that nonlinear Hamiltonian quantum mechanics does not admit cloning without the cloning machine. It is then demonstrated that the addition of the cloning machine, treated as a quantum or as a classical system, makes the cloning possible by nonlinear Hamiltonian evolution. However, a special type of quantum-classical theory, known as the mean-field Hamiltonian hybrid mechanics, does not admit cloning by natural evolution. The latter represents an example of a theory where it appears to be possible to communicate between two quantum systems at super-luminal speed, but at the same time it is impossible to clone quantum pure states.