1 Introduction

The abundance of nitrogen atoms in the Earth atmosphere and the great number of singly ionized nitrogen spectral lines (NII) in stars spectra make them important for plasma diagnostic purposes over a wide range of electron temperature. Namely, information on the chemical evolution of the elements in stars and stellar associations (Cuhna & Lambert 1994; Leuenhagen & Hamann 1998) and on the kinetics, dynamics and structure of the galaxies (Bland-Hawthorn et al. 1997), can be supplied on the basis of the NII spectral lines. If the Stark broadening is the principal pressure broadening mechanism in plasmas (with 10²²  $\rm m^{-3}-10^{27}$ $\rm m^{-3}$ electron density), on the basis of Stark width values it is possible to obtain other basic plasma parameters e.g. electron temperature (T) and density (N), essential in the modeling of the stellar atmospheres (Lesage 1994). It is of interest to find spectral lines with well-know Stark width values convenient in plasma diagnostics. A number of experimental papers deal with Stark FWHM (full-width at half intensity maximum, w) of singly ionized nitrogen spectral lines from multiplet $\ ^3{\rm P}^0 -\ ^3$P (No. 5) belonging to $\rm 3s-3p$ transition (Day & Griem 1965; Berg et al. 1967; Jalufka & Craig 1970; Konjevic et al. 1970; Popovic et al. 1975; Purcell & Barnard 1984; Puric et al. 1987; Djenize et al. 1990; Perez et al. 1997; Milosavljevic & Djenize 1998). The 463.054 nm spectral line, that belong to this multiplet, is the most investigated spectral line in the NII spectrum. Up to this time eight experiments (Berg et al. 1967; Jalufka & Craig 1970; Konjevic et al. 1970; Popovic et al. 1975; Purcell & Barnard 1984; Puric et al. 1987; Perez et al. 1997; Milosavljevic & Djenize 1998) deal with Stark FWHM investigation of this line. However, no theoretical Stark FWHM predictions exist for this line, to the knowledge of the authors (Fuhr & Lesage 1993). Experimental Stark FWHM data of the 463.054 nm spectral line lies in a wide range of the electron temperature, from 6500 K up to 54000 K. Most of the existing experimental w data lies about 22000 K electron temperature.

The aim of this paper is to provide some new experimental Stark FWHM data on 463.054 nm NII spectral line at electron temperatures between 30000 K and 38000 K. Namely, knowledge of the Stark FWHM dependence upon the electron temperature in the plasma is important for testing their theoretical predictions based on various approaches. We have measured the Stark FWHM of 436.054 nm NII spectral line at: 30000 K, 33000 K, 35000 K and 38000 K electron temperatures and correspondent electron densities: (0.75, 1.15, 1.30, 1.45) 10²³ $\rm m^{-3}$, respectively. The theoretical dependence of Stark width w on the electron temperature, on the basis of the modified semiempirical approximation (Dimitrijevic & Konjevic 1980) has been calculated as well.