N-I AND N-II SPECTRA AND MEAN LIFETIMES MEASURED BY A NEW TECHNIQUE OF BEAM-FOIL SPECTROSCOPY WITH A CHARGE-COUPLED-DEVICE

A new method for measuring spectra and decay curves in beam-foil spect roscopy is described and some initial results presented. A charge-coup led device (CCD) is used to record simultaneously all points on a deca y curve. A telecentric optical system ensures that the spectral resolv ance is close to the irreducible limit (set by angular divergence of t he atomic beam) and that no systematic distortion of the decay curve c an occur. Values of mean lifetimes are reported in N II for 11 levels derived from decay curves for 15 lines in the wavelength range 500-700 mum. In addition decay curves have been measured for 5 blends, each o f lines within the same N II multiplet; also some measurements for N I lines in the wavelength range 700-900 mum are reported.