No abstract

Accurate ab initio calculations are presented of the electronic factor F for the field isotope shift in the resonance line in K and for the hyperfine structure of the states involved. The relation between our calculated F value and that obtained from experimental hyperfine structure data is discussed. The isotope shift data by Touchard et al for the chain 38-47K are reanalysed and revised values for 8 ( r 2 ) are presented and compared with corresponding results for neighbouring Ca isotones.

We have combined the quasiparticle method in many-body perturbation theory with methods used when solving the coupled-cluster equations in order to evaluate the proper self-energy potential beyond second order in perturbation theory. The method is used to calculate the affinities of Ca and Sr including second-order relativistic effects. The result is 19 meV for Ca 2 4p 1͞2 and 54 meV for Sr 2 5p 1͞2 , which are in fair agreement with experiment. [S0031-9007(96)00040-3]

In this paper we apply the single-particle Green's-function method to the atomic many-body perturbation theory. We present an all-order evaluation scheme for the proper self-energy operator based on the systematic use of Dyson's integral equations. The method is complete to third order in perturbation theory and, in addition, large classes of higher-order effects are included by solving the Dyson equations. Certain classes of many-body correlation effects beyond the pair-correlation approximation are included. The proposed method is tested by calculating the ground-state valence-electron binding energy for the alkali-metal atoms Li, Na, and K. Agreement with experimental results corresponds to an error in the correlation energy contribution of 3-4 %. If certain three-particle effects, not evaluated in this work, are added, the agreement with experiments is, for sodium and potassium, approximately within 1% of the correlation energy.