@misc{AckermannHELFRICH, author = {Ackermann, J{\"o}rg and HELFRICH, K.}, title = {Radius of Convergence of the 1/Z-Expansion for Diatomic Molecules: The Ground State of the Isoelectronic H2Sequence.}, url = {http://nbn-resolving.de/urn:nbn:de:0297-zib-721}, number = {SC-92-02}, abstract = {Using the perturbational-variational Rayleigh-Ritz matrix formalism, the 1/Z-expansion for the ground state of the isoelectronic \$H_2\$ sequence in the range of the internuclear distance \$0.2\le R \le 9.0\$ is calculated. Also lower bounds of the radius of convergence, based on Kato's theory of linear operators, are given. The numerical results of the 1/Z-expansion can be compared with the exact results and do not converge in the whole R-range. This behavior is in qualitative agreement with the lower bounds for the radius of convergence and enlights some still open properties of 1/Z- expansions for this sequence in the literature. {\bf PACS:} 31.15 + q; 31.20 Di; 31.20 Tz.}, language = {en} }