Journal of Physical Studies 9(2), 156–162 (2005)
DOI: https://doi.org/10.30970/jps.09.156

THE PROPERTIES OF A TWO-PHASE FLUID OF TWO-LEVEL ATOMS, A PART OF WHICH IS EXCITED. A DENSITY FUNCTIONAL APPROACH

O. V. Derzhko¹, V. M. Myhal²
^{1}Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine,
1 Svientsitskii St., Lviv, UA–79011, Ukraine
^{2}Ivan Franko National University of Lviv, Department for Theoretical Physics,
12 Drahomanov St., UA–79005, Ukraine

Within the frames of the density functional approach we consider a problem about the properties of the nonuniform (two-phase) fluid of two-level atoms, a part of which is excited. We suggest a density functional of the grand thermodynamical potential which takes into account new effective long-range interactions between the identical differently excited atoms (resonance dipole-dipole interactions). We find the critical parameters, construct the phase diagram, examine the planar and spherical interphase surfaces, calculate the surface tension and the nucleation barier for vapour-to-liquid phase transition. We discuss the influence of the excited atoms on the properties of the two-phase atomic fluid.

PACS number(s): 64.70.Fx, 82.65.Dp, 62.60.Nh, 64.60.Qb