The electron nuclear dynamics theory (END) extended to include a time-
dependent external field is briefly described. The dynamical equations
, in addition to the full electron nuclear coupling Germs, now also co
ntain the interactions of both the nuclei and the electrons with the e
xternal field. This extended END theory is applied to the study of vib
rational excitations of the simple diatomics HF and LiH. The END resul
ts using an intense infrared laser field are compared with those of mo
lecular dynamics as well as those from quantum wave-packet calculation
s. While the effect of the nonadiabatic electron-nuclear coupling term
s on the vibrational dynamics is negligible for the chosen application
, the electron-field coupling has a significant impact. [S1050-2947(97
)04412-0].