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The effective electric field experienced by the unpaired electron in the ground state of PbF, which is a potential candidate in the search of electron electric dipole moment due to some special characteristics, is calculated using Z-vector method in the coupled cluster single- and double- excitation approximation with four component Dirac spinor. This is an important quantity to set the upper bound limit of the electron electric dipole moment. Further, we have calculated molecular dipole moment and parallel magnetic hyperfine structure constant (Aa) of 207Pb in PbF to test the accuracy of the wavefunction obtained in the Z-vector method. The outcome of our calculations clearly suggests that the core electrons have significant contribution to the gatom in compoundh properties. [ABSTRACT FROM AUTHOR]

Fock space multireference coupled-cluster (FSMRCC) method emerged as an efficient tool to describe the electronic structure of nearly degenerate cases. Development of linear response has been one of the challenging problems in FSMRCC due to the multiple-root nature of the effective Hamiltonian. A response from any of the roots would span the space for getting the properties. Hence, all roots perturbed by the external field would proliferate the excited states. We recently developed the FSMRCC method for the efficient evaluation of analytic response properties using a constrained variation approach. In this paper, we present analytic dipole moments and polarizabilities of H2O, O3, and CH+ molecules in low-lying excited states along with brief discussion of singlet triplet decoupling of (1,1) sector of FSMRCC resulting from spin adaptation. [ABSTRACT FROM AUTHOR]

Within the Fock-space multi-reference coupled cluster framework, we have evaluated the electronic transition dipole moments, which determine absorption intensities. These depend on matrix elements between two different wave functions (e.g., ground state to the excited state). We present two different ways, to calculate these transition moments. In the first method, we construct the ground and excited state wave functions with the normal exponential ansatz of Fock-space coupled cluster method and then calculate the relevant off-diagonal matrix elements. In the second approach, we linearize the exponential form of the wave operator which will generate the left vector, by use of Lagrangian formulation. The right vector is obtained from the exponential ansatz. In order to relate the transition moments to oscillator strengths, excitation energies need to be evaluated. The excitation energies are obtained from the Fock-space multi-reference framework. The transition dipole moments of the ground to a few excited states, together with the oscillator strengths of a few molecules, are presented. [ABSTRACT FROM AUTHOR]

Theoretical evaluation of molecular properties of excited states is extremely necessary as the lifetime of the excited states is too low for experimental probing. High level of theoretical treatment is an attractive option for the study of such states. However, theoretical calculation of this is a challenging task and in this paper we have presented such calculation using the analytic Fock space multireference coupled cluster linear response approach in a one hole-one particle model space. The results for the dipole moments of the adiabatic excited states of the water molecule are presented in this paper. The Sadlej basis set optimized for the property evaluation is used for the calculation and we address the adiabatic singlet B[sub 1] and triplet B[sub 1] excited states. The results using both the finite-field and the analytic response approach are presented. Full effective Hamiltonian including the three body terms in a singles and doubles approximation has been used for the calculation. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]