Cascade-corrected lifetimes of the 3p4 D3/2,5/2,7/2 energy levels in N III.

Abstract

A detailed cascade-corrected energy-level lifetime analysis of the 3${\mathit{p}}^{4}$ ${\mathit{D}}_{3/2,5/2,7/2}$ energy levels in N iii was undertaken by studying the 3p $^{4}$${\mathit{D}}_{\mathit{J}}$--3s $^{4}$${\mathit{P}}_{\mathit{J}}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$ transitions, as well as incorporating cascading from the higher-lying 3d $^{4}$${\mathit{P}}_{\mathit{J}}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$, 3d $^{4}$${\mathit{D}}_{\mathit{J}}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$, and 3d $^{4}$${\mathit{F}}_{\mathit{J}}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$ energy levels. The present paper therefore describes beam-foil measurements of the decay times of a number of 2${\mathit{s}}^{1}$2${\mathit{p}}^{1}$${(}^{3}$${\mathit{P}}^{\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}$)3p and 3d levels in N iii. These 3d levels were found to have a very marked influence of approximately 15% on the lifetimes of the 3p $^{4}$${\mathit{D}}_{\mathit{J}}$ energy levels. This influence was studied using a multiexponential curve-fitting technique, as well as the now well-proved (arbitrarily normalized decay curve) technique. The beam-foil method using these techniques is expected to provide a reliable and consistent experimental check on lifetime calculations.