Dmitry A. Fedorov and Sergey A. Varganov
Department of Chemistry, University of Nevada, Reno, 1664 N. Virginia St, Reno, Nevada 89557-0216.
Small molecules can be useful as qubits for quantum computing1 and for high-precision measurement of fundamental constants.2 One of the obstacles to practical implementation of these ideas is absorption of the black body radiation, which reduces the lifetime of these molecules in specific quantum state. We present the results of couple cluster and multireference configuration interaction calculations with Gaussian basis sets on diatomic and triatomic alkali molecules. In particular, we focus on dipole moment and its derivative with respect to interatomic distance, which related to the probability of transition between vibrational states. The convergence of the dipole moment with the size of the one-electron basis set is slow. A basis set of at least quadruple-zeta quality with additional core functions is required. If non-polarizable effective core potential is used the size of the core must be kept small. In contrast, the requirements for electronic structure method are mild. Accurate values of dipole moment can be obtained with couple cluster theory with singles and doubles.
1.DeMille, D. Phys. Rev. Lett. 88, 067901 (2002).
2.Vanhaecke, N. & Dulieu, O. Mol. Phys. 105, 1723-1731 (2007).
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