His more recent research is focused on theoretical studies of the electronic structure of molecules. Efforts in this area are directed at extending the quantum Monte Carlo method to the range of chemical problems that form the traditional domain of quantum chemistry, and beyond because of the capability of not imposing the Born-Oppenheimer approximation. Research by the Lester group has confirmed that highly accurate ground state and excited state energies are attainable by the method. Properties other than the energy including dipole and quadrupole moments as well as matrix elements connecting different electronic states have been determined following algorithms developed by his group. Dr. Lester's professional experience includes senior staff positions at the University of Wisconsin, Madison, and the IBM Research Division. During the period 1978-81, he was Director of the National Resource for Computation in Chemistry at Lawrence Berkeley National Laboratory and concurrently an Associate Director of the Laboratory. He is a Fellow of the American Physical Society, the American Association for the Advancement of Science, and of the California Academy of Science. He is a past member of the Department of Energy Advanced Scientific Computing Advisory Committee (2000-2004) and the Committee on the National Medal of Science (2000-2002) among others.