Quasi-metastable quartet levels in alkalilike atoms and ions.
TL;DR: The properties of a subclass of quartet levels of alkalilike atoms and ions that often retain metastability against autoionization and may have large radiative yields are described.
Abstract: We describe the properties of a subclass of quartet levels of alkalilike atoms and ions that often retain metastability against autoionization and may have large radiative yields. Gain cross sections for XUV lasers with wavelengths between 20 and 100 nm are given.
Summary (1 min read)
- Even in heavier elements, often retain relative metastability against autoionization and are radiatively allowed.the authors.
- In elements such as Cs and Ba these levels are candidates for the upper level of XUV lasers.
- The distinguishing property of, these quasi-metastable levels is that the selection rules on the spin-orbit matrix elements allow nonzero matrix elements only to doublet basis levels, which are themselves prohibited from autoionizing.
- In second order, through the diagonalization, these levels do develop components of autoionizing doublet levels and therefore do autoionize, but often sufficiently slowly that the branching ratio for XUV radiation remains large.
- Therefore, of the possible quartet levels, those that couple only to the nonautoionizing 2PI/2,3/ 2 levels are 4S3/2 and 4DI/2.
- Table 1 lists the quartet levels of the 2p53s3p configuration and their autoionizing rates as predicted by the atomic-physics code RCN/RCG,3 with only this configuration included.
- Single and double stars in the left-hand column denote predicted quasi-metastability and metastability, respectively.
- The nonzero autoionizing rates of the quasi-metastable levels result from small components of autoionizing doublet levels, which are acquired in second order through the diagonalization.
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