Relativistically prolonged lifetime of the 2s2p 3P0 level of zero nuclear-spin beryllium-like ions

S Fritzsche,A Surzhykov,A Volotka

doi:10.1088/1367-2630/17/10/103009

Abstract

The E1M1 transition rate of the line in beryllium-like ions has been calculated within the framework of relativistic second-order perturbation theory. Both multiconfiguration and quantum-electrodynamical computations have been carried out independently to better understand and test for all major electron–electron correlation contributions in the representation of the initial, intermediate and final states. By comparing the results from these methods, which agree well for all ions along the beryllium isoelectronic sequence, the lifetime of the metastable 2s2p 3P0 level is found to be longer by about 2–3 orders of magnitude for all medium and heavy elements than was estimated previously. This makes the 3P0 level of beryllium-like ions to one of the longest living (low-lying) electronic excitations of a tightly bound system with potential applications for atomic clocks and in astro physics and plasma physics.

Highlights

Since the beginning of atomic spectroscopy, metastable states have attracted much interest in studying electronic excitations in many-electron atoms and ions and their interaction with light and matter
The major difficulty in calculating the two-photon transition amplitude (1) and rates arises from the summation over the intermediate states and the extent to which the electron–electron correlation is taken into account in the representation of the atomic bound states
For the 1s22s2 1S0 ground state of beryllium-like ions, for example, sizeable correlation contributions are added by virtual double excitations of the 2s2 electrons into the 2p and 3s shells, and which can be omitted only for high-Z ions

Summary

Introduction

Since the beginning of atomic spectroscopy, metastable states have attracted much interest in studying electronic excitations in many-electron atoms and ions and their interaction with light and matter. E1M1 transition rates for beryllium-like ions with zero nuclear spin within the framework of relativistic second-order perturbation theory Both a series of multiconfiguration and quantum-electrodynamic computations have been carried out independently in order to explore how the correlated and relativistic motion of the electrons in the initial, intermediate, and final states affect the two-photon rates and lifetimes. From these computations, it is found that the lifetime of the metastable 2s2p 3P0 level is larger by about 2–3 orders of magnitude for all medium and heavy ions along the beryllium isoelectronic sequence than estimated previously. Apart from the relativistic contraction of the wave functions and the proper excitation energies to the levels nearby, especially the electronic correlations in the 2s2 1S0 ground state has been found relevant for predicting reasonably accurate lifetimes

Theory and computations

Results and discussion

Conclusions