We consider the control of internal conversion between the S _2(~1B _(2u)) excited electronic state of pyrazine and the S _1(~1B _(3u)) state. The study is performed both during and after the femtosecond excitation of the ground electronic state S _0(~1A _g) to form the S _2 state. The dynamics is examined using the newly developed effective modes technique which enables the full computation of quantum dynamics in multi-dimensional spaces. Using this technique, we also investigate the coherent control of population transfer from S _0 to the S _2 and S _1 electronic states. We find that the use of shaped laser pulses enables a significant delay of the internal conversion. For example, after 60 fs, the S _2 population amounts to ～60 of the initial S _0 population, and remains at ～20 after 100 fs, in contrast to the S _0 electronic state which is completely depopulated within 75 fs.
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