1. Department of Physics, Faculty of Science, J. E. Purkinje University, Ústí n. Lab., Czech Republic
2. E. Hála Laboratory of Thermodynamics, Institute of Chemical Process Fundamentals of the ASCR, v. v. i., Prague 6-Suchdol, Czech Republic
3. U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005-5066