We analyze a recently introduced method for canonically sampling classical phase space using Nose-Hoover chain constant temperature molecular dynamics. An advantage of this method is that a thermal ensemble can be generated without the use of a Monte-Carlo rejection procedure. The method is shown to give thermal distributions for two realistic molecular model systems, representing H2O and CF3NO, including rotational degrees of freedom. We demonstrate how the method can be extended to generate a ''bithermal'' sampling in which the rotational and vibrational degrees of freedom have different effective temperatures and how to adapt the results to include excitation of an initial thermal ensemble by a monochromatic light source, We also suggest a method for approximating the corresponding quantum distribution through a simple scaling of the classical distribution. (C) 1997 American Institute of Physics.