Stanke, MonikaKedziera, DariuszBubin, SergiyAdamowicz, Ludwik2016-02-012016-02-012007Monika Stanke, Dariusz Ke˛dziera, Sergiy Bubin, Ludwik Adamowicz; 2007; Lowest Excitation Energy of 9Be; PHYSICAL REVIEW LETTERShttp://nur.nu.edu.kz/handle/123456789/1128Variational calculations employing explicitly correlated Gaussian functions and explicitly including the nuclear motion [i.e., without assuming the Born-Oppenheimer (BO) approximation] have been performed to determine the lowest singlet transition energy in the 9Be atom. The non-BO wave functions were used to calculate the 2 relativistic corrections ( 1=137:035 999 679). With those corrections and with the 3 and 4 QED corrections determined previously by others, we obtained 54 677:35 cm 1 for the 31S ! 21S transition energy. This result falls within the error bracket for the experimental transition of 54 677:26 10 cm 1. This is the first time an electronic transition of Be has been calculated from first principles with the experimental accuracyenAttribution-NonCommercial-ShareAlike 3.0 United StatesResearch Subject Categories::NATURAL SCIENCES::Physics9Be atomBorn-Oppenheimer approximationArticle