A pulsed optical–optical double resonance study of the 1 1Πg state of 7Li2

Potential Energy Curves in the CASSCF/CASPT2 and FS-MR-CC Methods: The Role of Relativistic Effects

Ab initio CASSCF/CASPT2 calculations for the electronic ground and for a wide range of excited states of Li2 and Na2 dimers are presented. The computed spectroscopic parameters agree very well with the experimental data. This indicates that the old CASSCF/CASPT2 method can be as successfully applied to study excited states of molecules as recently developed the multireference Fock-space coulped-cluster method. The role of relativistic effects in the correct description of the potential energy curves has been investigated using as an example the SiAu molecule. The accuracy of the new infinite-order two-component relativistic method has been studied and its advantage over the Douglas-Kroll-Hess method demonstrated.

Experimental Study of the NaK 3(1)Pi State

We report the results of an optical-optical double resonance experiment to determine the NaK 3(1)Pi state potential energy curve. In the first step, a narrow band cw dye laser (PUMP) is tuned to line center of a particular 2(A)1Sigma+(v', J') <-- 1(X)1Sigma+(v", J") transition, and its frequency is then fixed. A second narrowband tunable cw Ti:Sapphirelaser (PROBE) is then scanned, while 3(1)Pi --> 1(X)1Sigma+ violet fluorescence is monitored. The Doppler-free signals accurately map the 3(1)Pi(v, J) ro-vibrational energy levels. These energy levels are then fit to a Dunham expansion to provide a set of molecular constants. The Dunham constants, in turn, are used to construct an RKR potential curve. Resolved 3(1)Pi(v, J) --> 1(X)1Sigma+(v", J") fluorescence scans are also recorded with both PUMP and PROBE laser frequencies fixed. Comparison between observed and calculated Franck-Condon factors is used to determine the absolute vibrational numbering of the 3(1)Pi state levels and to determine the variation of the 3(1)Pi --> 1(X)1Sigma+ transitiondipole moment with internuclear separation. The recent theoretical calculation of the NaK 3(1)Pi state potential reported by Magnier and Millié (1996, Phys. Rev. A 54, 204) is in excellent agreement with the present experimental RKR curve. Copyright 1999 Academic Press.

Precise Molecular Constants for the 6Li2 A1Sigma+u-X1Sigma+g System by Sub-Doppler Polarization Spectroscopy

We report here new and more accurate molecular constants from sub-Doppler polarization spectroscopy of the A1Sigma+u-X1Sigma+g system of 6Li2 using single mode cw dye lasers. These new constants cover the range of vibrational levels from v" = 0-8 in the ground state and v' = 0-24 in the excited state. New molecular constants and RKR potential energy curves for the A1Sigma+u and X1Sigma+g states are given. The Te value for the A1Sigma+u state is 14068.043(34) cm-1. The analysis indicates that there is a noticeable breakdown of the Born-Oppenheimer approximation for the 6Li2 and 7Li2 isotopomers. Copyright 1998 Academic Press.