  The abundance stratification in the ejecta of the normal Type Ia supernova
2002bo is derived by fitting a series of spectra obtained at close time
intervals. A Monte Carlo code, modified to include abundance stratification, is
used to compute synthetic spectra at 13 epochs in the photospheric phase,
starting 13d before B maximum. A description of the abundance distribution
above 7600 km/s is thus obtained. Abundances in deeper layers, down to zero
velocity, are derived from models of two nebular-phase spectra. Elements
synthesized in different stages of burning are significantly, but not
completely, mixed in the ejecta. A total 56Ni mass of 0.52M_sun is derived.
Evidence for intermediate-mass elements at high velocities (> 18 000 km/s) is
found, most clearly in Si II 6355A, in Ca II H&K, and in the Ca II infrared
triplet. Carbon lines are not seen at any velocity, with possible implications
for the progenitor/explosion scenario. A synthetic bolometric light curve
computed using the inferred abundance distribution is in very good agreement
with the observed one, providing an independent check. In particular, the fast
rise of the light curve is reproduced very well. This is due to outward mixing
of 56Ni, which is clearly well determined by the spectroscopic modelling.
