Stark broadening data for many transitions of many atoms and ions are needed for diagnosis of laboratory and astrophysical plasmas. As an example, data for more than 106 transitions, including line-profile parameters, are needed for the calculation of stellar opacities (Seaton 1988). With the development of space-borne spectroscopy, interest increases even more for a large number of spectral line profile parameters. For example, Leckrone et al. (1993) stated that with the Goddard High Resolution Spectrograph (GHRS) on Hubble Space Telescope they "have doubled the number of heavy elements () for which abundances in Lupi can be estimated, compared to ground-based data alone". Cardelli et al. (1991) have used the GHRS for investigation of spectra of the interstellar medium, which more accurately represents the pre-stellar material from which the Ap and Bp stars (where Stark broadening data are of interest) are formed (Leckrone et al. 1993). For the first time, they have begun to detect elements such as krypton and germanium.
Stark broadening for Kr II lines has additional theoretical interest for the investigation of regularities and systematic trends for singly-charged noble gas ions (e.g. Dimitrijevic & Popovic 1989; Di Rocco 1990; Puric et al. 1991; Bertuccelli & Di Rocco 1993). Stark broadening data for Xe II, which is homologous with Kr II, have been published recently (Popovic & Dimitrijevic 1996a). A consistent set of Stark broadening data for Kr II and Xe II enables the investigation and testing of regularities in the case of homologous atoms, as well as Stark width estimates for homologous sequences for noble gas ions.
Stark broadening of Kr II lines have been considered experimentally (see e.g. Brandt et al. 1981; Pittman & Konjevic 1986; Vitel & Skowronek 1987; Uzelac & Konjevic 1989; Lesage et al. 1989; Bertuccelli & Di Rocco 1991) and theoretically (see e.g. Bertuccelli & Di Rocco 1993). Bertuccelli & Di Rocco (1993) have calculated Kr II Stark widths for several lines by using analytical expressions for the cross sections and rate coefficients based on the Born approximation, with and without the empirical modification for the collision strength suggested by Robb and with the help of a semiempirical method (Griem 1968). Estimates also exist based on the dependence on atomic number and the upper level ionization potential, established from the consideration of regularities (Di Rocco 1990; Puric et al. 1991; Bertuccelli & Di Rocco 1991, 1993). Here we present Stark widths for 37 spectral lines from the transition array of singly-charged krypton, calculated by using a modified semiempirical approach (Dimitrijevic & Konjevic 1980; Dimitrijevic & Krsljanin 1986). Due to the complexity of the Kr II spectrum, calculations were performed as in Popovic & Dimitrijevic (1996b). Our results for Stark widths and shifts are compared with the available experimental and theoretical data.