Hidemi NAGAO, Hiroyuki KAWABE (Kinjo College), Koichi KODAMA* (*Kanazawa Univ.), Yasuteru SHIGETA*, Kiyoshi NISHIKAWA*, Masayoshi NAKANO** (**Osaka Univ.) and Kizashi YAMAGUCHI**
[Int. J. Quantum Chemistry 60, 1261 (1997)]
We have already developed the many-electron wavepackets (MEWP) method in order to study the dynamics and electronic structure of molecular systems. We extended the MEWP method to study the nonadiabatic effects and formulated a nonadiabatic molecular theory, where both electron and nucleus are treated equivalently. Then we applied our method to the isotope series of hydrogen molecule i.e.,H2,HD and D2, and calculated the total energy and the average distance between nucleus-nucleus, electron-electron, and electron-nucleus in order to analyze numerically the nonadiabatic effect in the molecule. Finally, we calculated the real-time evolution of the polarization by means of Chebyshev scheme, and by Fourier transforming this, we found out the excitation spectrum of the system, which corresponds to the electronic excitation and the nuclear vibrational frequency.