The equilibrium geometries of heteroatomic cluster AlLi~3 have been optimized with the energy gradient method using double-zeta plus polarization (DZP) basis set. The vertical excited energies and the oscillatior strengths have obtained from ab initio configuration interaction method. Transitions to 1^1B~1, 2^1B~1, 5^1A~1 of AlLi~3(C~2~v) and 1^1B~2, 2^1A~1, 3^1A~1 of AlLi~3(D~3~h→C~2~v) and 3^1B~2, 1^1B~1, 4^1A~1 of B~2Li~2(C~2~v) and 1^1B~2~u, 2^1B~1~u, 3^1B~3~u of Li~2B~2(D~2~h) have considerable values of oscillator. They are the single excitations (particle-hole transitions) dominate in states with large intensity.

Key words: QUANTUM CHEMISTRY, CLUSTER COMPOUND, EXCITED STATE, OSCILLATOR STRENGTH, VERTICAL, HETEROKARYON