Experimental results are presented for the rotational alignment of N-2(+)(v(')=0) as a function of both rotational state and component Doppler velocity. A single-frequency ring dye laser is used to probe the alignment of N-2(+) drifted in helium in a flow-drift apparatus by the technique of polarized laser-induced fluorescence. The collision-induced quadrupole rotational alignment parameter A(0)((2)) is determined as a function of the field direction component of sub-Doppler laboratory velocity at a fixed field strength of 12 Td for five rotational states. A dramatic difference in velocity-selected alignment as a function of rotational state is observed, with the higher rotational states exhibiting a greater degree of alignment than the lower rotational states. Additionally, for sufficiently low rotational state (J=11.5), A(0)((2)) changes sign across the Doppler profile, a behavior that has not previously been reported in the literature. A companion theoretical paper presents molecular dynamics calculations that are in excellent agreement with these experimental observations.