We investigate nuclear matter on a cubic lattice. An exact thermal formalism is applied to nucleons with a Hamiltonian that accommodates on-site and next-neighbor parts of the central, spin-, and isospin-exchange interactions. We describe the nuclear matter Monte Carlo methods which contain elements from shell model Monte Carlo methods and from numerical simulations of the Hubbard model. We show that energy and basic saturation properties of nuclear matter can be reproduced. Evidence of a first-order phase transition from an uncorrelated Fermi gas to a clustered system is observed by computing mechanical and thermodynamical quantities such as compressibility, heat capacity, entropy, and grand potential. We compare symmetry energy and first sound velocities with literature and find reasonable agreement.PACS number͑s͒: 21.65.ϩf, 21.60.Ka II. THEORY OF NUCLEONIC MATTER ON A LATTICEThe general concept of the nuclear matter calculation consists of nucleons interacting via a variety of components of PHYSICAL REVIEW C, VOLUME 61, 044320

We perform Hartree-Fock calculations to show that quantum dots ͑i.e., two-dimensional systems of up to twenty interacting electrons in an external parabolic potential͒ undergo a gradual transition to a spin-polarized Wigner crystal with increasing magnetic-field strength. The phase diagram and ground-state energies have been determined. We tried to improve the ground state of the Wigner crystal by introducing a Jastrow ansatz for the wave function and performing a variational Monte Carlo calculation. The existence of so-called magic numbers was also investigated. Finally, we also calculated the heat capacity associated with the rotational degree of freedom of deformed many-body states. ͓S0163-1829͑96͒04544-4͔

Crossed-beam measurements of rotationally inelastic scattering of H − ions from H 2 are reported for collision energies in the range E rel = 1.66-2.79 eV. From the energy-loss spectra of the scattered H − ions, state-specific differential cross sections in the CM system are derived for rotational transitions ranging from j = 1 → 3 to j = 1 → 13. Absolute units are obtained by using elastic H − + He scattering as a reference system. The measurements show a strong rotational excitation of the target molecule, while elastic scattering is nearly absent. The rotational levels j = 5, 7, 9 are found to be dominantly excited. The observations can be understood qualitatively from the properties of the H − 3 potential energy surface. Integral cross sections for rotationally inelastic scattering are estimated and compared with those for reactive scattering and electron detachment.

Experimental data for the Sherman function of xenon at collision energies between 50 and 150 eV are presented. The main idea of this investigation was to check the reliability of the experimental techniques by using two different and independent methods: the measurement of the polarization after scattering of unpolarized electrons and the measurement of the intensity asymmetry of polarized electrons scattered through the same scattering angle to the left and to the right. The agreement of the data from the two approaches is good. The results are compared with latest theories.

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