Abstract: Two vector operators aimed at shifting angular momentum quantum number l in spherical harmonics ｜lm〉,primarily proposed by X.L.Ka in 1999,are in fact first rank irreducible tensor operators.For a given magnetic quantum number m,specific state ｜lm〉 in spherical harmonics with the lowest angular momentum quantum number l is obtained and how to use this state to generate whole set of spherical harmonics is illustrated.

Key words: quantum mechanics, angular momentum, quantum number, raising and lowering operators