  Two vector operators aimed at shifting angular momentum quantum number l in
spherical harmonics |lm>, primarily proposed by Prof. X. L. Ka in 2001, are
further studied. For a given magnetic quantum number m, specific states |lm> in
spherical harmonics with the lowest angular momentum quantum numbers l are
obtained and the state with minimum angular momentum quantum number in whole
set of the spherical harmonics is |0,0>. How to use these states to generate
whole set of spherical harmonics is illustrated.
