Secondly, we also perform wave packet dynamics to probe the dynamical aspects of the RIXS process and investigate mechanism leading to the sharp feature in the RIXS at a 1g F1s XA resonance . We observe from our dynamical simulation that the steepness in potential energy surface of the intermediate state, i.e. the coreexcited state, has a profound role in the sharpness of the RIXS spectrum.