1999ApJ...525..881H

Synthetic spectra generated with the parameterized supernova synthetic-spectrum code SYNOW are compared with spectra of the Type Ia SN 1994D that were obtained before the time of maximum brightness. Evidence is found for the presence of two-component Fe II and Ca II features, forming in high-velocity (≥20,000 km.s^–1) and lower velocity (≤16,000 km.s^–1) matter. Possible interpretations of these spectral splits, and implications for using early-time spectra of Type Ia supernovae to probe the metallicity of the progenitor white dwarf and the nature of the nuclear burning front in the outer layers of the explosion, are discussed.