In experiments on excitons and spin-polarized atomic hydrogen, one deals with a gas involving two Bose branches (for example, paraexcitons and orthoexcitons). Based on a simple model for the coupling between these two components, we discuss how interconversion processes affect Bose condensation in such a system. Our analysis is based on an exact transformation to renormalized Bose particles which are uncoupled. We give results for the condensate fraction as a function of the temperature in the case when the two original Bose particles (a and b) are not in chemical equilibrium (i.e., the chemical potentials ${\mathrm{\mu }}_{\mathit{a}}$ and ${\mathrm{\mu }}_{\mathit{b}}$ are not equal) as well as in the case of chemical equilibrium (${\mathrm{\mu }}_{\mathit{a}}$=${\mathrm{\mu }}_{\mathit{b}}$). Our results are of interest in connection with current attempts to observe Bose condensation in atomiclike gases.

• Received 30 September 1994

DOI:https://doi.org/10.1103/PhysRevE.51.1075