Evidence for autoionization and dielectronic recombination of SI II in the atmospheres of B-type stars.

Abstract

Observations are reported demonstrating that both of the 3s3p3d ²F⁰ levels of Si II autoionize in the atmospheres of B-type stars. A justification is given for concluding that the ²F⁰_5/2 level which lies below the laboratory position for the 3s²(¹S) limit of Si II, autoionizes in stellar atmospheres. The ²F^7/2 level lies above the 3s²(¹S) limit and satisfies the selection rules for autoionization.

The occurrence in the atmosphere of P Cygni of dielectronic recombination from the 3s3p3d ²F⁰ levels of Si II is noted.