Molecular hyperfine parameters in the 1 3Σ u + and 1 3Σ g + states of Li2, Na2, K2 and Rb2

Diagonal and off-diagonal hyperfine structure matrix elements in KCs within the relativistic Fock space coupled cluster theory

“…2. The obtained R-dependencies of the 0 − -0 + coupling elements closely resemble those reported in [9] for the Fermi-contact interaction in the a 3 Σ + u state of homonuclear alkali dimers. The widely used assumption that the hyperfine coupling matrix elements are constant is not correct for the "bonding" region of potential curves (R < 8 Å) where the deviations from the corresponding atomic values reach 15% (see Fig.…”

“…It should be emphasized that in all the previous studies of HFS in alkali dimers the non-relativistic approximation to the Hamiltonian (1) was employed; the Fermicontact term was shown to be dominant in the HFS mixing of the X 1 Σ + and a 3 Σ + states [9]. The relativistic form of the HFS Hamiltonian (1) is more general and precise, including the paramagnetic spin-orbit, Fermicontact, and spin-dipole hyperfine operators.…”

“…Since the magnetic dipole hyperfine interaction is a one-electron property essentially defined by the behavior of the wavefunctions in the vicinity of nuclei, the HFS matrix element dependencies A(R) can be calculated for the K and Cs nuclei separately. The contributions to the hyperfine structure induced by nuclear electric quadrupole moments are negligible for alkali diatomics [9,29] and hence are not considered here. The values of nuclear dipole magnetic moments, µ39 K = 0.39147µ N and µ133 Cs = 2.582025µ N , were taken from Ref.…”

“…Most nonadiabatic models of the X 1 Σ + ∼ a 3 Σ + complex constructed to date assumed hyperfine interaction matrix elements to be constant with respect to the internuclear distance R, and thus their values were derived from the atomic ones (for example, see [1] and references therein). However, there are indications that the hyperfine interaction matrix elements actually depend on R at least in the bound region of potential energy curves (PECs) [8][9][10], but the character of this dependence is quite unclear since no highly reliable calculations of the HFS matrix elements in alkali diatomics were reported. The clarification of this question can not only justify the neglect of R-dependence for large values of R, but also bring the nonadiabatic models to a new level of accuracy which will be adequate to the current level of high-resolution molecular spectroscopy.…”

Level structure of deeply bound levels of the c3Σg+ state of Rb2

“…We now compare our results for c and b F to the recent theoretical work of Lysebo et al [21]. For the relevant internuclear distances the value of b F was calculated to vary between 850 and 810 MHz × h, which agrees with the rule-of-thumb estimate of b F ≈ A HF /4 [26,27], where A HF ≈ 3.42 GHz × h is the atomic hyperfine constant for 87 Rb in the electronic ground state [28].…”