I will present a simple method to analyze astrophysical spectra by comparison with line lists extracted from the NIST data base.

The method is useful when spectral features are dominated by single atomic transitions, and when a single expansion velocity

can be assumed for all relevant ions, i.e., when the photosphere is narrow in velocity space.

The method was developed for analysis of early spectra of supernovae (SNe), but is shown to be applicable to peak spectra of superluminous supernovae (SLSN).

Intriguing results are obtained when this method is applied to the excellent spectra of the recent binary neutron star kilonova source we obtained, and will be briefly discussed.