Radiative Lifetimes for uv Multiplets of N II through N V

Abstract

The foil-excitation technique has been used to measure radiative lifetimes of eighteen uv multiplets in N II through N V. The multiplets were produced by passing a ${\mathrm{N}}^{+}$ beam of known energy through a thin carbon foil that could be moved in small steps along the axis of the beam. The beam energy was either 1 or 2 MeV and the foil thickness either 500 or 1000 ÅA. A grazing-incidence monochromator instrumented for photoelectric counting was used to measure the decay of the multiplet as a function of distance downstream from the intersection of the foil and beam. The wavelengths of the measured multiplets were from 1085 ÅA (N II) to 162 ÅA (N V). Most of the multiplets were transitions to the ground-term configuration. The mean lifetimes range from about 3×${10}^{-9\mathrm{}}$ to 0.5×${10}^{-10\mathrm{}}$ sec, the measured accuracy being between 5 and 15%. Corrections for cascading were necessary for many of the multiplets. Transition probabilities obtained from the lifetime measurements are compared with other experimental and theoretical determinations.