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Using the temperature and ionization calculated in our previous paper, wemodel the spectral evolution of SN 1987A. The IR-catastrophe is seen in themetal lines as a transition from thermal to non-thermal excitation, mostclearly in the [O I] 6300, 6364 lines. The distribution of the different zones,and therefore the gamma-ray deposition, is determined from the line profiles ofthe most important lines, where possible. We find the total mass ofhydrogen-rich gas to be ~7.7 Msun. The helium mass derived from the line fluxesis sensitive to assumptions about the degree of redistribution in the line. Themass of the helium dominated zone is consistent with ~1.9 Msun, with a further~3.9 Msun of helium residing in the hydrogen component. Because ofuncertainties in the modeling of the non-thermal excitation of the [O I] lines,the uncertainty in the oxygen mass is considerable. In addition, masses ofnitrogen, neon, magnesium, iron and nickel are estimated. The dominantcontribution to the line luminosity often originates in a different zone fromwhere most of the newly synthesized material resides. This applies to e.g.carbon, calcium and iron. The [C I] lines, mainly arising in the helium zone,indicate a substantially lower abundance of carbon mixed with helium thanstellar evolution models give, and a more extended zone with CNO processed gasis indicated. The [Fe II] lines have in most phases a strong contribution fromprimordial iron, and at t > 600 - 800 days this component dominates the [Fe II]lines. The wings of the [Fe II] lines may therefore come from primordial iron,rather than synthesized iron mixed to high velocity. Lines from ions with lowionization potential indicate that the UV field below at least 1600 AA isseverely quenched by dust absorption and resonance scattering.Comment: 63 pages, including 22 figures; ApJ (Main Journal); scheduled for  April 10, 1998, Vol. 49

Late Spectral Evolution of SN 1987A. II. Line Emission