We study the second hyperpolarizabilities ( gamma) for 1-center radicals, i
e., BH3-, CH3 and NH3+. It is found that magnitudes of gamma(\gamma\) of th
e radicals are sensitively influenced by features of each charged state. It
is also found that electron-correlation dependence of gamma can be related
to the resonance structure contributing to the ground state of the molecul
es.