We propose a nonperturbative quantum dissipation theory, in term of
hierarchical quantum master equation. It may be used with a great degree of
confidence to various dynamics systems in condensed phases. The theoretical
development is rooted in an improved semiclassical treatment of Drude bath,
beyond the conventional high temperature approximations. It leads to the new
theory a simple modification but important improvement over the conventional
stochastic Liouville equation theory, without extra numerical cost. Its broad
range of validity and applicability is extensively demonstrated with two--level
electron transfer model systems, where the new theory can be considered as the
modified Zusman equation. We also present a criterion, which depends only on
the system--bath coupling strength, characteristic bath memory time, and
temperature, to estimate the performance of the hierarchical quantum master
equation.Comment: 10 pages, 8 figures, submitted to J. Chem. Phys. on 2009-08-0