This paper reports the experimental observation of the 2 3Σ+g, 3 3Σ+g, and 4 3Σ+g states of 7Li2 by cw perturbation facilitated optical–optical double resonance spectroscopy. Molecular constants and RKR potential curves have been obtained. Our experimental Te and Re for the 2 3Σ+g state are 27 297.45(16) cm−1 and 3.0797(18) Å, respectively, and for the 3 3Σ+g state are 31 043.93(53) cm−1 and 3.0378(19) Å, respectively. The above values are in very good agreement with theoretical calculations. Hyperfine splitting for both states has been resolved. Both states follow Hund’s case (bβS) hyperfine coupling scheme. The experimental Fermi contact parameter, bF, is approximately 96±2 MHz for the 2 3Σ+g state and 95.6±3 MHz for the 3 3Σ+g state. These values are in good agreement with the previously obtained value 98.6±4 MHz [Li et al., J. Chem. Phys. 96, 3342 (1992)]. One level of the 4 3Σ+g state has been observed and its hyperfine structure has been resolved and characterized with Hund’s coupling case (bβS).

This paper reports the first experimental observation of the doubly excited valence (2p+2p)3Σ−g state of 7Li2. We used cw perturbation-facilitated optical–optical double resonance (PFOODR) fluorescence excitation and resolved fluorescence spectroscopic techniques. All the observed levels have been detected through perturbations by the 2 3Πg state. The deperturbed primary molecular constants of this 1 3Σ−g state are Te=34 045.354(43) cm−1, ωe=216.820(37) cm−1, Be=0.673 69(47) cm−1, Re=2.670 81(94) Å, and De=4279.306(43) cm−1. The equilibrium internuclear distance of the 1 3Σ−g state is smaller than that of the X 1Σ+g ground state.

Articles you may be interested inHyperfine structures of the 7Li2 b 3Π u , 23Π g , and 33Π g states: Continuous wave perturbation facilitated optical-optical double resonance spectroscopy Perturbation facilitated optical-optical double resonance spectroscopy of the 23Σ+ g , 33Σ+ g , and 43Σ+ g Rydberg states of 7Li2 A pulsed optical-optical double resonance study of the 11Π g state of 7Li2The (2pϩ2p) 2 3 ⌸ g and (2sϩ3 p) 3 3 ⌸ g states of 7 Li 2 have been studied both experimentally and theoretically. Vibrational levels vϭ0 -41 of the 2 3 ⌸ g state and vϭ6 -10 of the 3 3 ⌸ g state have been observed by perturbation facilitated optical-optical double resonance ͑PFOODR͒ spectroscopy. Our ab initio calculations show that the 2 3 ⌸ g state, although dissociating into 2 pϩ2 p atomic limit, is a Rydberg state and strongly mixed with the (2sϩ3p) 3 3 ⌸ g and (2sϩ3d) 4 3 ⌸ g Rydberg states. Our theoretical calculations show good agreement with our experimental results.

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This paper reports measurements of the homogeneous predissociation of the Li2 F 1Σg+ state due to electrostatic interaction with the E 1Σg+ state. Ab initio potential energy curves have been calculated for both states which in the adiabatic representation show two avoided crossings. However, predissociation was not previously predicted. Our experimental results show that the three isotopomers Li27, Li76Li, and Li26 all strongly predissociate above the 2s+3s atomic limit. We report high resolution measurements of linewidths for a large number of F–state levels spread across the 2600 cm−1 energy region between the 2s+3s and 2p+2p atomic limits, which yield systematic information regarding the rotational, vibrational, and isotopomer dependence of the predissociation rate. An experimental RKR potential energy curve for the F state is derived and used to calculate predissociation rates whose trends show good agreement with the experimental values. This paper presents the first complete data set of observations on the predissociation rate of a diatomic molecule and its variation with v and J when the interaction with the perturbing state takes place at two distinct internuclear distances.