Book Description

The equation of state of an ionized gas has been investigated for electron densities below about 10(22 power) per cubic centimeter and temperatures below about 1,000,000 K. The gas is assumed to be monatomic, electrically neutral, and in thermodynamic equilibrium, but the composition of the gas is arbitrary, that is multiple ionization of any degree is allowed. The perfect gas approximation is found to be valid for electron densities at least as high as 10(16 power) per cubic centimeter, and in some cases, even higher. It is shown that approximations to the perfect gas expressions can be made which will greatly simplify calculations. It is also shown that blackbody radiation may be important at low densities. The classical corrections to the perfect gas expressions due to electrostatic forces and the finite size of particles which are obtained from the theories of Debye and Hucke, Mayer, and others, are investigated, and their limits of validity are determined. In some cases, improved expressions are derived and suitable approximations are suggested. It is noted that a fundamental weakness of the results based on the these theories is that a basic parameter, the distance of closest approach of charged particles, is not known accurately. Several approximate expressions for this distance are given. Quantum corrections for electron degeneracy and electron interactions are also given. Theories which are applicable at higher densities and temperatures than those of interest in this investigation are also discussed briefly. Finally, the equation of state of a dense, slightly ionized gas is derived.